Editing Tsetse fly

{{short description|Genus of disease-spreading insects}}
{{use dmy dates |date=April 2023}}
{{redirect|Tsetse}}
{{Automatic taxobox
| image = Glossina-morsitans.jpg
| image_caption = ''[[Glossina morsitans]]''
| display_parents = 6
| fossil_range = [[Eocene]] - [[Recent]] {{fossilrange|34|0}}
| parent_authority = [[Frederick Vincent Theobald|Theobald]], 1903
| taxon = Glossina
| authority = [[Christian Rudolph Wilhelm Wiedemann|Wiedemann]], 1830
| subdivision_ranks = Species groups
| subdivision = * '''''Morsitans''''' ("savannah" subgenus)
* '''''Fusca''''' ("forest" subgenus)
* '''''Palpalis''''' ("riverine" subgenus)
| range_map = Tsetse distribution.png
| range_map_caption = Range of the tsetse fly
}}

'''Tsetse''' ({{IPAc-en|ˈ|s|iː|t|s|i}} {{respell|SEET|see}}, {{IPAc-en|us|ˈ|t|s|iː|t|s|i}} {{respell|TSEET|see}} or {{IPAc-en|uk|ˈ|t|s|ɛ|t|s|ə}} {{respell|TSET|sə}}) (sometimes spelled '''tzetze'''; also known as '''tik-tik''' flies) are large, [[biting flies]] that inhabit much of tropical [[Africa]].<ref>{{Cite journal |last=Ford |first=J. |title=The distribution of the vectors of African pathogenic trypanosomes |url=https://iris.who.int/bitstream/handle/10665/266946/PMC2554952.pdf |journal= Bulletin of the World Health Organization|date=1963 |volume=28 |issue=5–6 |pages=653–669 |pmid=13958704 |pmc=2554952 }}</ref><ref>{{Citation |last1=Rogers |first1=D. J. |title=Tsetse distribution. |date=January 2004 |work=The trypanosomiases |pages=139–179 |editor-last=Maudlin |editor-first=I. |url=http://www.cabidigitallibrary.org/doi/10.1079/9780851994758.0139 |access-date=2024-10-28 |edition=1 |place=UK |publisher=CABI Publishing |language=en |doi=10.1079/9780851994758.0139 |isbn=978-0-85199-475-8 |last2=Robinson |first2=T. P. |editor2-last=Holmes |editor2-first=P. H. |editor3-last=Miles |editor3-first=M. A.}}</ref><ref name=":0">{{Cite book |last1=Cecchi |first1=G. |url=https://openknowledge.fao.org/handle/20.500.14283/cd2022en |title=The continental atlas of the distribution of tsetse flies in Africa |last2=Paone |first2=M. |last3=de Gier |first3=J. |last4=Zhao |first4=W. |date=2024 |publisher=FAO |isbn=978-92-5-139040-5 |series=PAAT Technical and Scientific Series, No. 12. |location=Rome |language=English |doi=10.4060/cd2022en}}</ref> Tsetse flies include all the species in the [[genus]] '''''Glossina''''', which are placed in their own family, '''Glossinidae'''. The tsetse is an [[obligate parasite]], which lives by feeding on the [[blood]] of [[vertebrate]] animals. Tsetse has been extensively studied because of their role in transmitting disease. They have pronounced economic and public health impacts in sub-Saharan Africa as the [[Vector (epidemiology)|biological vectors]] of [[trypanosomes]], causing [[African trypanosomiasis|human]] and [[animal trypanosomiasis]].<ref>{{Cite book |last=Swallow |first=B. M. |url=https://openknowledge.fao.org/handle/20.500.14283/x4755en |title=Impacts of Trypanosomiasis on African agriculture |publisher=FAO |year=2000 |isbn=978-92-5-104413-1 |series=PAAT Technical and Scientific Series, No. 2 |location=Rome}}</ref><ref>{{Cite journal |last1=Büscher |first1=Philippe |last2=Cecchi |first2=Giuliano |last3=Jamonneau |first3=Vincent |last4=Priotto |first4=Gerardo |date=November 2017 |title=Human African trypanosomiasis |url=https://linkinghub.elsevier.com/retrieve/pii/S0140673617315106 |journal=The Lancet |language=en |volume=390 |issue=10110 |pages=2397–2409 |doi=10.1016/S0140-6736(17)31510-6|pmid=28673422 }}</ref> 

Tsetse can be distinguished from other large flies by two easily-observed features: primarily, tsetse fold their wings over their [[abdomen]]s completely when they are resting (so that one wing rests directly on top of the other); Secondly, tsetse also have a long [[proboscis]], extending directly forward, which is attached by a distinct bulb to the bottom of their heads.

[[Fossilized]] tsetse has been recovered from [[Paleogene]]-aged rocks in the United States and Germany. Twenty-three extant species of tsetse flies are known from the African continent as well as the Arabian Peninsula.

==Terminology==
''Tsetse'' without the "fly" has become more common in [[English language|English]], particularly in the scientific and development communities.

The word is pronounced {{IPA|tn|tsɛtsɛ|}} (''tseh-tseh'') in the [[Sotho languages]] and is easily rendered in other African languages. During World War II, a British [[de Havilland]] antisubmarine aircraft known as the ''[[De Havilland Mosquito#Strike ("fighter-bomber") variants|Tsetse Mosquito]]''<ref>{{cite book |title=Anti-Submarine Warfare: An Illustrated History |year=2007 |author-first=David | author-last=Owen |page=170 |publisher= Naval Institute Press| isbn= 9781591140146 | url= https://books.google.com/books?id=gCrYwAEACAAJ}}</ref> helped establish the term in commonplace use among native English speakers.

==Biology==
The biology of tsetse is relatively well understood by [[Entomology|entomologists]]. They have been extensively studied because of their medical, veterinary, and economic importance, because the flies can be raised in a laboratory, and because they are relatively large, facilitating their analysis.

===Morphology===
Tsetse flies can be seen as independent individuals in three forms: as third-[[instar]] larvae, pupae, and adults.

Tsetse first becomes separate from their mothers during the third larval instar, during which they have the typical appearance of [[Fly#Maggots|maggots]]. However, this life stage is short, lasting at most a few hours, and is almost never observed outside of the laboratory.

Tsetse next develops a hard external case, the puparium, and become pupae - small, hard-shelled oblongs with two distinctively small, dark lobes at the tail (breathing) end. Tsetse pupae are under {{ convert | 1 | cm | in | frac=4 }} long.<ref name="Jordan">{{Cite book |author=A. M. Jordan |year=1986 |title=Trypanosomaisis control and African rural development |publisher=London and New York: [[Longman]]}}</ref> Within the puparial shell, tsetse complete the last two larval instars and the pupal stage.

At the end of the pupal stage, tsetse emerges as adult flies. The adults are relatively large flies, with lengths of {{ convert | 0.5 | - | 1.5 | cm | in | frac=8 }},<ref name="Jordan"/> and have a recognizable shape, or [[bauplan]], which makes them easy to distinguish from other flies. Tsetse have large heads, distinctly separated eyes, and unusual antennae. The [[Thorax (insect anatomy)|thorax]] is quite large, while the abdomen is wider, rather than elongated, and shorter than the wings.

Four characteristics collectively separate adult tsetse from other kinds of flies:
{|class="wikitable"
|-
| '''Proboscis''' || Tsetse have a distinct proboscis, a long and thin structure attached to the bottom of the head, pointing forward. || [[Image:tsetse head-proboscis.jpeg|center|70px|A photograph of the head of a tsetse illustrating the forward pointing proboscis]]
|-
| '''Folded wings''' || When at rest, tsetse fold their wings completely, one-on-top of the other. || [[Image:tsetse foldedWings.jpeg|center|200px|A photograph of the whole body of a tsetse illustrating the folded wings when at rest]]
|-
| '''Hatchet cell''' || The discal medial ("middle") cell of the wing has a characteristic hatchet shape, resembling a meat cleaver or a hatchet. || [[Image:tsetse hatchetCell.jpeg|center|140px|A photograph of the wing of a tsetse illustrating the hatchet shaped central cell]]
|-
| '''Branched arista hairs''' || The antennae have arista with hairs which are, themselves, branched. || [[Image:tsetse aristaHairs labeled.jpeg|center|140px|A photograph and diagram of the head of a tsetse illustrating the branched hairs of the antenna's arista]]
|}

===Anatomy===
Like all other [[insect]]s, tsetse flies have an adult body comprising three visibly distinct parts: the head, the thorax, and the abdomen.

The head has large eyes, distinctly separated on each side, and a distinct, forward-pointing proboscis attached underneath by a large bulb. The thorax is large, made of three fused segments. Three pairs of legs are attached to the thorax, as are two wings and two [[halteres]]. The abdomen is short but wide and changes dramatically in volume during feeding.

[[File:Gándulas de la leche de Glossina .gif|thumb|left|Reproductive anatomy sketch]]
The internal anatomy of the tsetse is fairly typical of the [[insect]]s; the [[crop (anatomy)|crop]] is large enough to accommodate a huge increase in size during feeding, as tsetse can take a blood meal equal in weight to themselves. The [[dipteran crop]] is heavily understudied, with ''Glossina'' being one of the few genera having relatively reliable information available: Moloo and Kutuza 1970 for ''G. brevipalpis'' (including its innervation) and Langley 1965 for ''G. morsitans''.<ref name="Stoffolano-Haselton-2013" /> The reproductive tract of adult females includes a [[uterus]], which can become large enough to hold the third-instar [[larva]] at the end of each [[pregnancy]].[[File:Dipteran-fly-structure.jpg|thumb|upright=1.75|1-Complex mouthparts, 2-Paired antennae, 3-Head, 4-Compound eye, 5-Thorax, 6-Open tube heart, 7-Salivary gland, 8-One pair of wings, 9-Halter, 10-Excretory (Malpighian) tube, 11-Gut, 12-Ovary (or testis), 13-Abdomen, 14-Legs (3 pairs), 15-Thoracic ganglion of nervous system, 16-Spiracle opening to respiratory tube (trachea)]]

Most tsetse flies are, physically, very tough. Houseflies, and even horseflies, are easily killed with a flyswatter, for example; a great deal of effort is needed to crush a tsetse fly.<ref name="Mavhunga-2018">{{cite book |author=[[Clapperton Chakanetsa Mavhunga]] |url=https://mitpress.universitypressscholarship.com/view/10.7551/mitpress/9780262535021.001.0001/upso-9780262535021-chapter-001 |title=The Mobile Workshop: The Tsetse Fly and African Knowledge Production |year=2018 |isbn=978-0-262-53502-1 |doi=10.7551/mitpress/9780262535021.001.0001}}</ref>

{{clear}}

===Life cycle===
[[File:glossina palpalis morsitans.jpg |upright=1.35|right|thumb|''Glossina palpalis'' and ''G. morsitans'' from a 1920 lexicon]]

Tsetse has an unusual [[Biological life cycle|life cycle]], which may be due to the richness of their blood food source. A female fertilizes only one egg at a time; she will retain each egg within her uterus, the offspring developing internally (during the first three [[Instar|larval stages]]), in an adaptation called [[adenotrophic viviparity]].<ref name="Vreysen-et-al-2013">{{cite journal | last1=Vreysen | first1=Marc J.B. | last2=Seck | first2=Momar Talla | last3=Sall | first3=Baba | last4=Bouyer | first4=Jérémy | title=Tsetse flies: Their biology and control using area-wide integrated pest management approaches | journal=[[Journal of Invertebrate Pathology]] | publisher=[[Academic Press]] ([[Elsevier]])| volume=112 | year=2013 | issn=0022-2011 | doi=10.1016/j.jip.2012.07.026 | pages=S15–S25 | s2cid=20005358 | pmid=22878217}}</ref> During this time, the female feeds the developing offspring with a milky substance (secreted by a modified gland) in the uterus.<ref>{{cite journal |author1=Geoffrey M. Attardoa |author2=Claudia Lohs |author3=Abdelaziz Heddi |author4=Uzma H. Alama |author5=Suleyman Yildirim |author6=Serap Aksoy |title=Analysis of milk gland structure and function in ''Glossina morsitans'': Milk protein production, symbiont populations and fecundity |journal=Journal of Insect Physiology |volume=54 |issue=8 |date=August 2008 |pages=1236–1242 |doi=10.1016/j.jinsphys.2008.06.008|pmid=18647605 |pmc=2613686 }}</ref>
In the third larval stage, the tsetse larvae leave the uterus and begin an independent life. The newly-birthed larvae crawl into the ground and develop a hard outer shell (called the [[puparium|puparial case]]), within which they complete their morphological transformations into adult flies.<ref name=slapeta2024>{{cite web|url=https://www.merckvetmanual.com/integumentary-system/flies/tsetse-flies|title=Tsetse Flies, Professional Version|last=Šlapeta|first=Jan|website=Merck Manual Veterinary Manual|version=Professional Version|access-date=18 February 2025|date=September 2024|orig-date=Originally published August 2022}}</ref><ref>{{cite web|url=https://animaldiversity.org/accounts/Glossina_morsitans/|title=''Glossina morsitans''|last=Fraumann|first=Robert|website=Animal Diversity Web|editor-last1=Diamond|editor-first1=Sara|editor-last2=David|editor-first2=Solomon|year=2003|access-date=18 February 2025}}</ref>

The larval life stage has a variable duration, ranging from four<ref name=benoit2021>{{cite journal|last1=Benoit|first1=Joshua B.|last2=Lahondère|first2=Chloé|last3=Attardo|first3=Geoffrey M.|last4=Michalkova|first4=Veronika|last5=Oyen|first5=Kennan|last6=Xiao|first6=Yanyu|last7=Aksoy|first7=Serap|title=Warm Blood Meal Increases Digestion Rate and Milk Protein Production to Maximize Reproductive Output for the Tsetse Fly, ''Glossina morsitans''|journal=Insects|volume=13|issue=11|year=2021|doi=10.3390/insects13110997|doi-access=free|id=Art. No. 997|hdl=10919/112559|hdl-access=free}}</ref> to ten days,<ref name=slapeta2024/> and the larvae must rely on the resources shared by the mother. The importance of the richness and quality of blood to this stage can be seen; all tsetse development (prior to emerging from the puparial case as a full adult after 35 days<ref name=slapeta2024/>) occurs with only the nutrition provided by the mother fly. She must get enough energy for her own survival, as well as for the resources that her offspring, whose mass can exceed that of the mother,<ref>{{cite journal|last1=Haines|first1=Lee R.|last2=Vale|first2=Glyn A.|last3=Barreaux|first3=Antoine M.G.|last4=Ellstrand|first4=Norman C.|last5=Hargrove|first5=John W.|last6=English|first6=Sinead|title=Big Baby, Little Mother: Tsetse Flies Are Exceptions to the Juvenile Small Size Principle|journal=BioEssays|volume=42|issue=11|id=Art. No. 2000049|year=2020|doi=10.1002/bies.202000049|doi-access=free}}</ref> will require until it emerges as an adult.<ref name=benoit2021/>  Both the male and female tsetse flies feed on blood, however.<ref>{{cite journal|title=Blood meal analysis of tsetse flies (''Glossina pallidipes'': Glossinidae) reveals higher host fidelity on wild compared with domestic hosts|journal=Wellcome Open Research|volume=6|year=2021|last1=Channumsin|first1=Manun|last2=Ciosi|first2=Marc|last3=Masiga|first3=Dan|last4=Auty|first4=Harriet|last5=Turner|first5=C. Michael|last6=Kilbride|first6=Elizabeth|last7=Mable|first7=Barbara K.|doi=10.12688/wellcomeopenres.16978.1|pmid=34703903|pmc=8513123|doi-access=free|id=Art. No. 213|version=Version 1}}</ref>

Technically, these insects undergo the standard [[morphogenesis|development]] process of insects, beginning with [[oocyte]] formation, ovulation, fertilization, and development of the egg; following egg development and birth is the three [[larva]]l stages, a [[pupa]]l stage, and the emergence and maturation of the adult.{{citation needed|date=September 2019}}

===Hosts===
Overall [[Suidae]] are the most important hosts. [[Waterbuck]] (''Kobus ellipsiprymnus'') are unmolested by ''Glossina''<ref name="FAO-distro" /><ref name="Glasgow-1967">{{cite journal |last=Glasgow |first=J. P. |year=1967 |title=Recent Fundamental Work on Tsetse Flies |journal=[[Annual Review of Entomology]] |publisher=[[Annual Reviews (publisher)|Annual Reviews]] |volume=12 |issue=1 |pages=421–438 |doi=10.1146/annurev.en.12.010167.002225 |issn=0066-4170 |pmid=5340724}}</ref> because they produce [[Volatile organic compound#Biologically generated VOCs|volatiles]] which act as [[Insect repellent|repellents]]. Waterbuck odor volatiles are under testing and development as repellents to protect [[livestock]].<ref name="Abro-et-al-2021">{{cite journal |last1=Abro |first1=Zewdu |last2=Kassie |first2=Menale |last3=Muriithi |first3=Beatrice |last4=Okal |first4=Michael |last5=Masiga |first5=Daniel |last6=Wanda |first6=Gift |last7=Gisèle |first7=Ouedraogo |last8=Samuel |first8=Abah |last9=Nguertoum |first9=Etienne |last10=Nina |first10=Rock Aimé |last11=Mansinsa |first11=Philémon |last12=Adam |first12=Yahaya |last13=Camara |first13=Mamadou |last14=Olet |first14=Pamela |last15=Boucader |first15=Diarra |display-authors=5 |date=2021-07-20 |editor-last=Simuunza |editor-first=Martin Chtolongo |title=The potential economic benefits of controlling trypanosomiasis using waterbuck repellent blend in sub-Saharan Africa |journal=[[PLoS ONE]] |publisher=[[Public Library of Science]] |volume=16 |issue=7 |page=e0254558 |bibcode=2021PLoSO..1654558A |doi=10.1371/journal.pone.0254558 |issn=1932-6203 |pmc=8291668 |pmid=34283848 |id=MK [[ORCID]] [http://orcid.org/0000-0002-6754-2432 0000-0002-6754-2432] |doi-access=free |last16=Jamal |first16=Susana |last17=Garba |first17=Abdoul Razak Issa |last18=Ajakaiye |first18=Joseph Joachim |last19=Kinani |first19=Jean Felix |last20=Hassan |first20=Mohamed Adam |last21=Nonga |first21=Hezron |last22=Daffa |first22=Joyce |last23=Gidudu |first23=Ambrose |last24=Chilongo |first24=Kalinga}}</ref><ref name="Cook-et-al-2007">{{cite journal |last1=Cook |first1=Samantha M. |last2=Khan |first2=Zeyaur R. |last3=Pickett |first3=John A. |year=2007 |title=The Use of Push-Pull Strategies in Integrated Pest Management |journal=[[Annual Review of Entomology]] |publisher=[[Annual Reviews (publisher)|Annual Reviews]] |volume=52 |issue=1 |pages=375–400 |doi=10.1146/annurev.ento.52.110405.091407 |issn=0066-4170 |pmid=16968206 |s2cid=23463014}}</ref>{{rp|Suppl T1}} By species, bloodmeals are derived from:<ref name="FAO-distro">{{cite web | title=Tsetse biology, systematics and distribution, techniques | website=[[Food and Agriculture Organization]] of the [[United Nations]] | url=https://www.fao.org/3/p5178e/P5178E06.htm | access-date=2021-02-20 | archive-date=30 November 2021 | archive-url=https://web.archive.org/web/20211130072337/https://www.fao.org/3/p5178e/P5178E06.htm | url-status=dead }}</ref>
{| class="wikitable"
|+
!Species
!Hosts
|-
|''[[Glossina swynnertoni|G. swynnertoni]]''
|
* 60{{endash}}70% from [[warthog]]
* ~8% from [[giraffe]]
|-
|''[[Glossina austeni|G. austeni]]'' 
|
* 50{{endash}}60% from [[bushpig]]
* ~33% from [[Bovidae]]
* possibly 10% from various [[duiker]]
|-
|''[[Glossina fuscipleuris|G. fuscipleuris]]'' 
|
* 65% from bushpig and [[giant forest hog]]
* up to 20% from [[hippopotamus]]
|-
|''[[Glossina tabaniformis|G. tabaniformis]]'' 
|
* 70% from [[red river hog]]
* >7% from [[Old World porcupine|porcupine]]s
|-
|''[[Glossina morsitans|G. morsitans]]''
|
* 30{{endash}}45% from warthog
* 25{{endash}}40% from various Bovidae, especially [[kudu]], [[African buffalo|buffalo]], [[Cape bushbuck|bushbuck]], and [[Taurotragus|eland]], most especially [[domestic cattle]]
* ~2% from [[hartebeest]]
|-
|''[[Glossina fusca|G. fusca]]'' 
|
* 55{{endash}}90% from [[Cape bushbuck|bushbuck]]
* 15% from red river hog
* ~12% from [[aardvark]]
|-
|''[[Glossina brevipalpis|G. brevipalpis]]'' 
|
* up to 40% (high variability with geography) from bushpig
* up to 36% from hippopotamus
* ~25% from Bovidae, especially buffalo and bushbuck
|-
|''[[Glossina palpalis|G. palpalis]]'' 
|
* ~3% from wild Suidae, more substantial amounts from [[domestic pig|domestic Suidae]] when available
* ~20{{endash}}40% from Bovidae (including domestic cattle) depending on geography
* ~10% from waterside birds including [[cormorant]]s
* 25{{endash}}30% from ''[[Varanus]]'' and [[crocodile]] (possibly higher in natural settings
* 50% from crocodile in particular locations)
|-
|''[[Glossina fuscipes|G. fuscipes]]''
|
* ~3% from wild Suidae
* ~20{{endash}}40% from Bovidae (including domestic cattle) depending on geography
* ~10% from waterside birds including [[cormorant]]s
* 25{{endash}}30% from ''[[Varanus]]'' and [[crocodile]] (possibly higher in natural settings)
|-
|''[[Glossina tachinoides|G. tachinoides]]''
|
* ~3% from wild Suidae, more substantial amounts from [[domestic pig|domestic Suidae]] when available
* ~20{{endash}}40% from Bovidae (including domestic cattle) depending on geography
* >7% from porcupines
|-
|''[[Glossina pallidipes|G. pallidipes]]'' 
|
* 55{{endash}}90% from [[Cape bushbuck|bushbuck]]
|-
|''[[Glossina longipalpis|G. longipalpis]]''
|
* 55{{endash}}90% from [[Cape bushbuck|bushbuck]]
|-
|''[[Glossina longipennis|G. longipennis]]'' 
|
* unusually dependant (~60%) on [[rhinoceros]]
* ~20% from Bovidae
* variably up to 12% from [[elephant]]
* up to 7% from [[ostrich]]
|-
|''[[Glossina morsitans submorsitans|G. m. submorsitans]]''
|
* ~6% from various birds excluding ostrich
|}

===Genetics===
The genome of ''Glossina morsitans'' was sequenced in 2014.<ref name="Watanabe-et-al-2014">{{cite journal | last1=International Glossina Genome Initiative: Attardo | first1=G. M. | last2=Abila | first2=P. P. | last3=Auma | first3=J. E. | last4=Baumann | first4=A. A. | last5=Benoit | first5=J. B. | last6=Brelsfoard | first6=C. L. | last7=Ribeiro | first7=J. M. C. | last8=Cotton | first8=J. A. | last9=Pham | first9=D. Q. D. | last10=Darby | first10=A. C. | last11=Van Den Abbeele | first11=J. | last12=Denlinger | first12=D. L. | last13=Field | first13=L. M. | last14=Nyanjom | first14=S. R. G. | last15=Gaunt | first15=M. W. | last16=Geiser | first16=D. L. | last17=Gomulski | first17=L. M. | last18=Haines | first18=L. R. | last19=Hansen | first19=I. A. | last20=Jones | first20=J. W. | last21=Kibet | first21=C. K. | last22=Kinyua | first22=J. K. | last23=Larkin | first23=D. M. | last24=Lehane | first24=M. J. | last25=Rio | first25=R. V. M. | last26=Macdonald | first26=S. J. | last27=Macharia | first27=R. W. | last28=Malacrida | first28=A. R. | last29=Marco | first29=H. G. | last30=Marucha | first30=K. K. | last31=Masiga | first31=D. K. | last32=Meuti | first32=M. E. | last33=Mireji | first33=P. O. | last34=Obiero | first34=G. F. O. | last35=Koekemoer | first35=J. J. O. | last36=Okoro | first36=C. K. | last37=Omedo | first37=I. A. | last38=Osamor | first38=V. C. | last39=Balyeidhusa | first39=A. S. P. | last40=Peyton | first40=J. T. | last41=Price | first41=D. P. | last42=Quail | first42=M. A. | last43=Ramphul | first43=U. N. | last44=Rawlings | first44=N. D. | last45=Riehle | first45=M. A. | last46=Robertson | first46=H. M. | last47=Sanders | first47=M. J. | last48=Scott | first48=M. J. | last49=Dashti | first49=Z. J. S. | last50=Snyder | first50=A. K. | last51=Srivastava | first51=T. P. | last52=Stanley | first52=E. J. | last53=Swain | first53=M. T. | last54=Hughes | first54=D. S. T. | last55=Tarone | first55=A. M. | last56=Taylor | first56=T. D. | last57=Telleria | first57=E. L. | last58=Thomas | first58=G. H. | last59=Walshe | first59=D. P. | last60=Wilson | first60=R. K. | last61=Winzerling | first61=J. J. | last62=Acosta-Serrano | first62=A. | last63=Aksoy | first63=S. | last64=Arensburger | first64=P. | last65=Aslett | first65=M. | last66=Bateta | first66=R. | last67=Benkahla | first67=A. | last68=Berriman | first68=M. | last69=Bourtzis | first69=K. | last70=Caers | first70=J. | last71=Caljon | first71=G. | last72=Christoffels | first72=A. | last73=Falchetto | first73=M. | last74=Friedrich | first74=M. | last75=Fu | first75=S. | last76=Gade | first76=G. | last77=Githinji | first77=G. | last78=Gregory | first78=R. | last79=Hall | first79=N. | last80=Harkins | first80=G. | last81=Hattori | first81=M. | last82=Hertz-Fowler | first82=C. | last83=Hide | first83=W. | last84=Hu | first84=W. | last85=Imanishi | first85=T. | last86=Inoue | first86=N. | last87=Jonas | first87=M. | last88=Kawahara | first88=Y. | last89=Koffi | first89=M. | last90=Kruger | first90=A. | last91=Lawson | first91=D. | last92=Lehane | first92=S. | last93=Lehvaslaiho | first93=H. | last94=Luiz | first94=T. | last95=Makgamathe | first95=M. | last96=Malele | first96=I. | last97=Manangwa | first97=O. | last98=Manga | first98=L. | last99=Megy | first99=K. | last100=Michalkova | first100=V. | last101=Mpondo | first101=F. | last102=Mramba | first102=F. | last103=Msangi | first103=A. | last104=Mulder | first104=N. | last105=Murilla | first105=G. | last106=Mwangi | first106=S. | last107=Okedi | first107=L. | last108=Ommeh | first108=S. | last109=Ooi | first109=C.-P. | last110=Ouma | first110=J. | last111=Panji | first111=S. | last112=Ravel | first112=S. | last113=Rose | first113=C. | last114=Sakate | first114=R. | last115=Schoofs | first115=L. | last116=Scolari | first116=F. | last117=Sharma | first117=V. | last118=Sim | first118=C. | last119=Siwo | first119=G. | last120=Solano | first120=P. | last121=Stephens | first121=D. | last122=Suzuki | first122=Y. | last123=Sze | first123=S.-H. | last124=Toure | first124=Y. | last125=Toyoda | first125=A. | last126=Tsiamis | first126=G. | last127=Tu | first127=Z. | last128=Wamalwa | first128=M. | last129=Wamwiri | first129=F. | last130=Wang | first130=J. | last131=Warren | first131=W. | last132=Watanabe | first132=J. | last133=Weiss | first133=B. | last134=Willis | first134=J. | last135=Wincker | first135=P. | last136=Zhang | first136=Q. | last137=Zhou | first137=J.-J. | display-authors=5 | title=Genome Sequence of the Tsetse Fly (''Glossina morsitans''): Vector of African Trypanosomiasis | id=NIHMSID: NIHMS591386 | journal=[[Science (journal)|Science]] | publisher=[[American Association for the Advancement of Science]] (AAAS) | volume=344 | issue=6182 | date=2014-04-24 | issn=0036-8075 | doi=10.1126/science.1249656 | pages=380–386 | s2cid=206554402 | pmc=4077534 | pmid=24763584| bibcode=2014Sci...344..380. }}</ref>

===Symbionts===
Tsetse flies have at least three bacterial [[Endosymbiont|symbionts]]. The primary symbiont is ''Wigglesworthia'' (''[[Wigglesworthia glossinidia]]''), which live within the fly's [[bacteriocyte]]s. The second symbiont is ''[[Sodalis (genus)|Sodalis]]'' (''[[Sodalis glossinidius]]'') intercellularly or intracellularly, and the third is some kind of ''[[Wolbachia]]''.<ref name="Kanté TagueuFarikou2018">{{cite journal|last1=Kanté Tagueu |first1=Sartrien|last2=Farikou|first2=Oumarou|last3=Njiokou|first3=Flobert|last4=Simo|first4=Gustave|title=Prevalence of ''Sodalis glossinidius'' and different trypanosome species in ''Glossina palpalis palpalis'' caught in the Fontem sleeping sickness focus of the southern Cameroon|journal=Parasite |volume=25|year=2018|page=44|issn=1776-1042|doi=10.1051/parasite/2018044|pmid=30117802|pmc=6097038}} {{open access}}</ref><ref name="SimoKanté2019">{{cite journal|last1=Simo|first1=Gustave|last2=Kanté |first2=Sartrien Tagueu|last3=Madinga|first3=Joule|last4=Kame|first4=Ginette|last5=Farikou|first5=Oumarou |last6=Ilombe|first6=Gillon|last7=Geiger|first7=Anne|last8=Lutumba|first8=Pascal|last9=Njiokou |first9=Flobert |title=Molecular identification of ''Wolbachia'' and ''Sodalis glossinidius'' in the midgut of ''Glossina fuscipes quanzensis'' from the Democratic Republic of Congo|journal=Parasite |volume=26|year=2019|page=5|issn=1776-1042|doi=10.1051/parasite/2019005|pmid=30729921|pmc=6366345}} {{open access}}</ref>

===Diseases===
The salivary gland hypertrophy virus causes abnormal bleeding in the lobes of the [[crop (dipteran)|crop]] of ''[[Glossina morsitans centralis|G. m. centralis]]'' and ''[[Glossina morsitans morsitans|G. m. morsitans]]''.<ref name="Stoffolano-Haselton-2013">{{cite journal | last1=Stoffolano | first1=John G. | author-link=John Stoffolano | last2=Haselton | first2=Aaron T. | title=The Adult Dipteran Crop: A Unique and Overlooked Organ | journal=[[Annual Review of Entomology]] | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=58 | issue=1 | date=2013-01-07 | issn=0066-4170 | doi=10.1146/annurev-ento-120811-153653 | pages=205–225| pmid=23317042 }}</ref>

==Systematics==
Tsetse flies are members of the order [[Diptera]], the true flies. They belong to the superfamily Hippoboscoidea, in which the tsetse's family, the Glossinidae, is one of four families of blood-feeding obligate parasites.

Up to 34 species and subspecies of tsetse flies are recognized, depending on the particular classification used.

Current classifications place all species of tsetse fly in a single genus named ''Glossina'', with most considering the genus as the sole member of the family Glossinidae.

===Species===
{{more citations needed section|date=October 2020}}
The tsetse genus is generally split into three groups of species based on a combination of distributional, ecological, behavioral, molecular and morphological characteristics.<ref name="Krafsur-2009">{{cite journal | last=Krafsur | first=E.S. | title=Tsetse flies: Genetics, evolution, and role as vectors | journal=[[Infection, Genetics and Evolution]] | publisher=[[Elsevier]] | volume=9 | issue=1 | year=2009 | issn=1567-1348 | doi=10.1016/j.meegid.2008.09.010 | pages=124–141 | s2cid=36305169 | pmid=18992846 | pmc=2652644}}</ref><ref>{{Cite journal |last=Cecchi |first=G. |last2=Mattioli |first2=R. C. |last3=Slingenbergh |first3=J. |last4=De La Rocque |first4=S. |title=Land cover and tsetse fly distributions in sub‐Saharan Africa |url=https://resjournals.onlinelibrary.wiley.com/doi/10.1111/j.1365-2915.2008.00747.x |journal=Medical and Veterinary Entomology |language=en |volume=22 |issue=4 |pages=364–373 |doi=10.1111/j.1365-2915.2008.00747.x |issn=0269-283X}}</ref> The genus includes; savannah flies, forest flies and riverine and lacustrine flies.<ref>{{Cite journal |last=Marchiori |first=Carlos Henrique |date=2021 |title=Study of the characteristics of the Glossinidae family (Muscoidea, Oestroidea) |url=https://sciresjournals.com/ijstra/content/study-characteristics-glossinidae-family-muscoidea-oestroidea |journal=International Journal of Science and Technology Research Archive |language=en |volume=1 |issue=2 |pages=088–107 |doi=10.53771/ijstra.2021.1.2.0050 |issn=0799-6632}}</ref>

==== Savannah flies ====
[[File:Geographic distribution of the morsitans group, subgenus Glossina s.s., as reported in scientific papers – Publication period 1990–2020.png|thumb|Geographic distribution of the morsitans group, subgenus Glossina s.s., as reported in scientific papers – Publication period 1990–2020]]
The 'savannah' flies: (''Morsitans group'', subgenus ''Glossina'' s.s.):
* ''[[Glossina austeni]]'' <small>([[Robert Newstead|Newstead]], 1912) [[patronymic taxon|patr.]] of [[Ernest Edward Austen|Austen]]</small>
* ''[[Glossina longipalpis]]'' <small>(Wiedemann, 1830)</small>
* ''[[Glossina morsitans]]'' <small>(Westwood, 1851)</small>
** ''[[Glossina morsitans morsitans]] (Westwood, 1850)''
** ''[[Glossina morsitans submorsitans]]''<ref name="Gooding-Krafsur-2005" />
** ''[[Glossina morsitans centralis]]'' (Machado, 1970) 
* ''[[Glossina pallidipes]]'' <small>([[Ernest Edward Austen|Austen]], 1903)</small>
* ''[[Glossina swynnertoni]]'' <small>([[Ernest Edward Austen|Austen]], 1923)<ref name="swyn-GBIF">[[GBIF]]: {{GBIF|id=5055987}} 5055987</ref><ref name="Austen-1922" /> [[patronymic taxon|patr.]] of [[Charles Francis Massy Swynnerton|Swynnerton]]</small><ref name="Austen-1922">{{cite journal | last=Austen | first=E. E. | author-link=Ernest Edward Austen | title=A New East African Tsetse-fly (Genus ''Glossina'', Wied.), which apparently disseminates sleeping sickness | journal=[[Bulletin of Entomological Research]] | publisher=[[Cambridge University Press|CUP]] | volume=13 | issue=3 | date=1922 | issn=0007-4853 | doi=10.1017/s0007485300045417 | pages=311–315 | s2cid=86238434| url=https://www.biodiversitylibrary.org/part/49465 }}</ref>

==== Forest flies ====
[[File:Geographic distribution of the fusca group, subgenus Austenina, as reported in scientific papers – Publication period 1990–2020.png|thumb|Geographic distribution of the fusca group, subgenus Austenina, as reported in scientific papers – Publication period 1990–2020]]
The 'forest' flies: (''Fusca'' group, subgenus ''Austenina''):
<!--<small>(Newstead and Evans, 1921)</small> [what is this - G.fusca austenia?] -->
* ''[[Glossina brevipalpis]]'' <small>(Newstead, 1910)</small>
* ''[[Glossina fusca]]'' <small>(Walker, 1849)</small>
** ''[[Glossina fusca fusca]]'' <small>(Walker, 1849)</small>
** ''[[Glossina fusca congolensis]]'' <small>(Newstead and Evans, 1921)</small>
* ''[[Glossina fuscipleuris]]'' <small>([[Ernest Edward Austen|Austen]], 1911)</small>
* ''[[Glossina frezili]]'' <small>(Gouteux, 1987)</small><ref name="Gouteux-1987">{{cite journal |author=J. P. Gouteux |title=Une nouvelle glossine du Congo: ''Glossina'' (''Austenina'') ''frezili'' sp. nov. (Diptera: Glossinidae) |journal=[[Tropical Medicine and Parasitology]]|volume=38 |issue=2 |year=1987 |pages=97–100 |pmid=3629143|s2cid=91006636|trans-title=A new tsetse fly from the Congo: ''Glossina (Austenina) frezili'' sp. nov. (Diptera: Glossinidae)|publisher=[[Deutsche Tropenmedizinische Gesellschaft]]|language=fr}}</ref>
* ''[[Glossina haningtoni]]'' <small>([[Robert Newstead|Newstead]] and Evans, 1922)</small>
* ''[[Glossina longipennis]]'' <small>(Corti, 1895)</small>
* ''[[Glossina medicorum]]'' <small>([[Ernest Edward Austen|Austen]], 1911)</small>
* ''[[Glossina nashi]]'' <small>(Potts, 1955)</small>
* ''[[Glossina nigrofusca]] <small>([[Robert Newstead|Newstead]], 1911)</small>''
** ''[[Glossina nigrofusca nigrofusca]]'' <small>([[Robert Newstead|Newstead]], 1911)</small>
** ''[[Glossina nigrofusca hopkinsi]]'' <small>(van Emden, 1944)</small>
* ''[[Glossina schwetzi]]'' <small>([[Robert Newstead|Newstead]] and Evans, 1921)</small>
* ''[[Glossina severini]]'' <small>([[Robert Newstead|Newstead]], 1913)</small>
* ''[[Glossina tabaniformis]]'' <small>(Westwood, 1850)</small>
* ''[[Glossina vanhoofi]]'' <small>(Henrard, 1952)</small>

==== Riverine and lacustrine flies ====
[[File:Geographic distribution of palpalis group, subgenus Nemorhina, as reported in scientific papers – Publication period 1990–2020.png|thumb|Geographic distribution of palpalis group, subgenus Nemorhina, as reported in scientific papers – Publication period 1990–2020]]
The 'riverine' and 'lacustrine' flies: (''Palpalis'' group, subgenus ''Nemorhina''):
* ''[[Glossina caliginea]]'' <small>([[Ernest Edward Austen|Austen]], 1911)</small>
* ''[[Glossina fuscipes]]'' <small>([[Robert Newstead|Newstead]], 1911)</small>
** ''[[Glossina fuscipes fuscipes]]'' <small>([[Robert Newstead|Newstead]], 1911)</small><ref name="Gooding-Krafsur-2005" />
** ''[[Glossina fuscipes martinii]]'' <small>(Zumpt, 1935)</small>
** ''[[Glossina fuscipes quanzensis]]'' <small>(Pires, 1948)</small>
* ''[[Glossina pallicera]] <small>(Bigot, 1891)</small>''
** ''[[Glossina pallicera pallicera]]'' <small>(Bigot, 1891)</small>
** ''[[Glossina pallicera newsteadi]]'' <small>([[Ernest Edward Austen|Austen]], 1929) [[patronymic taxon|patr.]] of [[Robert Newstead|Newstead]]</small>
* ''[[Glossina palpalis]]'' <small>(Robineau-Desvoidy, 1830)</small>
** ''[[Glossina palpalis palpalis]]'' <small>(Robineau-Desvoidy, 1830)</small>
** ''[[Glossina palpalis gambiensis]]'' <small>(Vanderplank, 1911)</small>
* ''[[Glossina tachinoides]]'' <small>(Westwood, 1850)</small>

=== Evolutionary history ===
Fossil glossinids are known from the [[Florissant Formation]] in North America and the [[Enspel Lagerstätte]] of Germany, dating to the late [[Eocene]] and late [[Oligocene]] respectively.<ref>{{Cite journal|last1=Wedmann|first1=Sonja|last2=Poschmann|first2=Markus|last3=Hörnschemeyer|first3=Thomas|date=2010-03-01|title=Fossil insects from the Late Oligocene Enspel Lagerstätte and their palaeobiogeographic and palaeoclimatic significance|journal=Palaeobiodiversity and Palaeoenvironments|language=en|volume=90 |issue=1|pages=49–58|doi=10.1007/s12549-009-0013-5|bibcode=2010PdPe...90...49W |issn=1867-1608|doi-access=free}}</ref>

==Range==
[[File:Geographic_distribution_of_tsetse_flies,_genus_Glossina,_in_Africa_as_reported_in_scientific_papers_%E2%80%93_Publication_period1990%E2%80%932020.png|thumb|400px|Geographic distribution of tsetse flies, genus Glossina, in Africa as reported in scientific papers – Publication period1990–2020]]
''Glossina'' is almost entirely restricted to wooded grasslands and forested areas of the [[Afrotropics]]. As of 1990, tsetse flies were reported from a maximum latitude of approximately 15° north in Senegal (Niayes Region), to a minimum of 28.5° south in South Africa (KwaZulu-Natal Province).<ref name=":0" />

Only two subspecies - ''[[Glossina fuscipes fuscipes|G. f. fuscipes]]'' and ''[[Glossina morsitans submorsitans|G. m. submorsitans]]'' - are present in the very southwest of Saudi Arabia. Although Carter found ''[[Glossina tachinoides|G. tachiniodes]]'' in 1903 nearby, near [[Aden]] in southern Yemen, there have been no confirmations since.<ref name="Gooding-Krafsur-2005">{{cite journal | last1=Gooding | first1=R.H. | last2=Krafsur | first2=Elliot Scoville | title=Tsetse Genetics: Contributions to Biology, Systematics, and Control of Tsetse Flies | journal=[[Annual Review of Entomology]] | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=50 | issue=1 | year=2005 | issn=0066-4170 | doi=10.1146/annurev.ento.50.071803.130443 | pages=101–123| pmid=15355235 | pmc=1462949 }}</ref>

==Trypanosomiasis==
[[File:Trypanosoma sp. PHIL 613 lores.jpg|thumb|[[Trypanosomes]] in a blood smear]]

Tsetse are [[Vector (epidemiology)|biological vectors]] of [[trypanosomes]], meaning that in the process of feeding, they acquire and then transmit small, single-celled trypanosomes from [[infection|infected]] [[vertebrate]] [[host (biology)|hosts]] to uninfected animals. Some tsetse-transmitted trypanosome species cause [[trypanosomiasis]], an infectious disease. In humans, tsetse transmitted trypanosomiasis is called [[African trypanosomiasis|sleeping sickness]].<ref>{{cite web |title=Trypanosomiasis, human African (sleeping sickness) |url=https://www.who.int/en/news-room/fact-sheets/detail/trypanosomiasis-human-african-(sleeping-sickness) |website=www.who.int |access-date=14 May 2020 |language=en}}</ref> In animals, tsetse-vectored trypanosomiases include ''nagana'', ''souma'' (a French term which may not be a distinct condition<ref name="Battista-Researchgate">{{ cite web | url=https://www.researchgate.net/publication/40893277 | title=Capanna E. Battista Grassi entomologist and the Roman School of Malariology. Parassitologia. 2008 Dec;50(3-4):201-11. PMID: 20055229.
 }}</ref>), and ''[[surra]]'' according to the animal infected and the trypanosome species involved. The usage is not strict and while ''nagana'' generally refers to the disease in cattle and horses it is commonly used for any of the animal trypanosomiases.

Trypanosomes are animal [[parasite]]s, specifically [[protozoa]]ns of the genus ''Trypanosoma''. These organisms are about the size of red blood cells. Different species of trypanosomes infect different hosts. They range widely in their effects on the vertebrate hosts. Some species, such as ''T. theileri'', do not seem to cause any health problems except perhaps in animals that are already sick.<ref name="Hoare">{{cite book |author=C. A. Hoare |chapter=Systematic Description of the Mammalian Trypanosomes of Africa |editor1=H. Mulligan |editor2=W. Potts |year=1970 |title=The African Trypanosomiases |publisher=London, UK: [[Allen and Unwin|George Allen and Unwin Ltd.]] |isbn=0-04-614001-8}}</ref>

Some [[strain (biology)|strains]] are much more [[virulence|virulent]]. Infected flies have an altered salivary composition which lowers feeding efficiency and consequently increases the feeding time, promoting trypanosome transmission to the vertebrate host.<ref>{{cite journal |title=Trypanosoma brucei Modifies the Tsetse Salivary Composition, Altering the Fly Feeding Behavior That Favors Parasite Transmission|journal=[[PLOS Pathogens]] |year=2010 |volume=6 |issue=6 |author1=Jan Van Den Abbeele |author2=Guy Caljon |author3=Karin De Ridder |author4=Patrick De Baetselier |author5=Marc Coosemans |doi=10.1371/journal.ppat.1000926 |pmid=20532213 |pages=e1000926|pmc=2880569 |doi-access=free }}</ref> These trypanosomes are highly evolved and have developed a life cycle that requires periods in both the vertebrate and tsetse hosts.

Tsetse transmit trypanosomes in two ways, mechanical and biological transmission.
*Mechanical transmission involves the direct transmission of the same individual trypanosomes taken from an infected host into an uninfected host. The name 'mechanical' reflects the similarity of this mode of transmission to mechanical injection with a [[syringe]]. Mechanical transmission requires the tsetse to feed on an infected host and acquire trypanosomes in the blood meal, and then, within a relatively short period, to feed on an uninfected host and regurgitate some of the infected blood from the first blood meal into the tissue of the uninfected animal. This type of transmission occurs most frequently when tsetse are interrupted during a blood meal and attempt to satiate themselves with another meal. Other flies, such as [[horse-fly|horse-flies]], can also cause mechanical transmission of trypanosomes.<ref>{{cite journal |title=Seasonal prevalence of bovine trypanosomosis in a tsetse-infested zone and a tsetse-free zone of the Amhara Region, north-west Ethiopia |journal=Onderstepoort Journal of Veterinary Research|year=2004 |volume=71 |issue=4 |pages=307–12 |author1=T. Cherenet |author2=R. A. Sani |author3=J. M. Panandam |author4=S. Nadzr |author5=N. Speybroeck |author6=P. van den Bossche |pmid=15732457 |doi=10.4102/ojvr.v71i4.250|doi-access=free }}</ref>
*Biological transmission requires a period of incubation of the trypanosomes within the tsetse host. The term 'biological' is used because trypanosomes must reproduce through several generations inside the tsetse host during the period of incubation (development within the fly is known as the extrinsic incubation period), which requires extreme [[Adaptation (biology)|adaptation]] of the trypanosomes to their tsetse host. In this mode of transmission, trypanosomes reproduce through several generations, changing in morphology at certain periods. This mode of transmission also includes the sexual phase of the trypanosomes. Tsetse are believed to be more likely to become infected by trypanosomes during their first few blood meals. Tsetse infected by trypanosomes are thought to remain infected for the remainder of their lives. Because of the adaptations required for biological transmission, trypanosomes that can be transmitted biologically by tsetse cannot be transmitted in this manner by other insects.

The relative importance of these two modes of transmission for the propagation of tsetse-vectored trypanosomiases is not yet well understood. However, since the sexual phase of the trypanosome life cycle occurs within the tsetse host, biological transmission is a required step in the life cycle of the tsetse-vectored trypanosomes.

The cycle of biological transmission of trypanosomiasis involves two phases, one inside the tsetse host and the other inside the vertebrate host. Trypanosomes are not passed between a pregnant tsetse and her offspring, so all newly emerged tsetse adults are free of infection. An uninfected fly that feeds on an infected vertebrate animal may acquire trypanosomes in its proboscis or gut. These trypanosomes, depending on the species, may remain in place, move to a different part of the digestive tract, or migrate through the tsetse body into the salivary glands. When an infected tsetse bites a susceptible{{dubious | reason=Unlikely to selectively transmit only to susceptible hosts |date=October 2020}} host, the fly may regurgitate part of a previous blood meal that contains trypanosomes, or may inject trypanosomes in its saliva. Inoculation must contain a minimum of 300 to 450 individual trypanosomes to be successful, and may contain up to 40,000 cells.<ref name="Hoare"/>

In the case of ''T. b. brucei'' infecting ''G. p. gambiensis'', during this time the parasite changes the [[proteome]] contents of the fly's head. This may be the reason/a reason for the behavioral changes seen, especially the unnecessarily increased feeding frequency, which increases transmission opportunities. This may be due in part to the altered [[glucose]] metabolism observed, causing a perceived need for more calories. (The metabolic change, in turn, being due to complete absence of [[Glucose-6-phosphate dehydrogenase|glucose-6-phosphate 1-dehydrogenase]] in infected flies.) [[Monoamine neurotransmitter]] synthesis is also altered: Production of [[aromatic L-amino acid decarboxylase]] - involved in [[dopamine]] and [[serotonin]] synthesis - and [[α-methyldopa hypersensitive protein]] was induced. This is very similar to the alterations in ''other'' [[fly|dipteran]] vectors' head proteomes under infection by ''other'' eukaryotic parasites of mammals, found in another study by the same team in the same year.<ref name="Lefevre-et-al-2007">{{cite journal | last1=Lefèvre | first1=T. | last2=Thomas | first2=F. | last3=Ravel | first3=S. | last4=Patrel | first4=D. | last5=Renault | first5=L. | last6=Le Bourligu | first6=L. | last7=Cuny | first7=G. | last8=Biron | first8=D. G. | title=''Trypanosoma brucei brucei'' induces alteration in the head proteome of the tsetse fly vector ''Glossina palpalis gambiensis'' | journal=[[Insect Molecular Biology]] | publisher=[[Royal Entomological Society]] ([[Wiley Publishing|Wiley]]) | volume=16 | issue=6 | date=2007-12-17 | issn=0962-1075 | doi=10.1111/j.1365-2583.2007.00761.x | pages=651–660 | pmid=18092995 | s2cid=3134104| url=https://hal.archives-ouvertes.fr/hal-02308250 }}</ref>

The trypanosomes are injected into vertebrate muscle tissue,{{citation needed|date=December 2015}} but make their way, first into the [[lymphatic system]], then into the bloodstream, and eventually into the brain. The disease causes the swelling of the lymph glands, emaciation of the body, and eventually leads to death. Uninfected tsetse may bite the infected animal prior to its death and acquire the disease, thereby closing the transmission cycle.

===Disease hosts and vectors===

The tsetse-vectored trypanosomiases affect various vertebrate species including humans, antelopes, bovine cattle, camels, horses, sheep, goats, and pigs. These diseases are caused by several different trypanosome species that may also survive in wild animals such as crocodiles and monitor lizards. The diseases have different distributions across the African continent, so are transmitted by different species. This table summarizes this information:<ref name="Hoare"/><ref>{{cite web |author=R. C. Hunt |year=2004 |url=http://www.med.sc.edu:85/trypanosomiasis.htm |title=Trypanosomiasis page, "Microbiology and Immunology On-line" |publisher=[[University of South Carolina]] |access-date=2005-04-02 }}{{Dead link|date=September 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
{| class="wikitable"
|-
! Disease !! Species affected !! ''Trypanosoma'' agents !! Distribution !! ''Glossina'' vectors
|-
| '''[[African trypanosomiasis|Sleeping sickness]]''' — chronic form || humans || ''T. brucei gambiense'' || Western Africa ||
* ''G. palpalis''
* ''G. tachinoides''
* ''G. fuscipes''
* ''G. morsitans''
|-
| '''[[African trypanosomiasis|Sleeping sickness]]''' — acute form || humans || ''T. brucei rhodesiense'' || Eastern Africa ||
* ''G. morsitans''
* ''G. swynnertoni''
* ''G. pallidipes''
* ''G. fuscipes''
|-
| '''[[Nagana]]''' — acute form || antelope<br />cattle<br />camels<br />horses || ''T. brucei brucei'' || Africa ||
* ''G. morsitans''
* ''G. swynnertoni''
* ''G. pallidipes''
* ''G. palpalis''
* ''G. tachinoides''
* ''G. fuscipes''
|-
| '''[[Nagana]]''' — chronic form || cattle<br />camels<br />horses || ''T. congolense'' || Africa ||
* ''G. palpalis''
* ''G. morsitans''
* ''G. austeni''
* ''G. swynnertoni''
* ''G. pallidipes''
* ''G. longipalpis''
* ''G. tachinoides''
* ''G. brevipalpis''
|-
| '''[[Nagana]]''' — acute form || domestic pigs<br />cattle<br />camels<br />horses || ''T. simiae''<ref name="CABI-ISC">{{ cite web | url=http://www.cabi.org/isc/datasheet/60778 | title=Trypanosoma simiae - CABI Invasive Species Compendium|website=Cabi.org}}</ref> || Africa ||
* ''G. palpalis''
* ''G. fuscipes''
* ''G. morsitans''
* ''G. tachinoides''
* ''G. longipalpis''
* ''G. fusca''
* ''G. tabaniformis''
* ''G. brevipalpis''
* ''G. vanhoofi''
* ''G. austeni''
|-
| '''[[Nagana]]''' — acute form || cattle<br />camels<br />horses || ''T. vivax'' || Africa ||
* ''G. morsitans''
* ''G. palpalis''
* ''G. tachinoides''
* ''G. swynnertoni''
* ''G. pallidipes''
* ''G. austeni''
* ''G. vanhoofi''
* ''G. longipalpis''
|-
| '''[[Surra]]''' — chronic form || domestic pigs<br />[[warthog]]<br/>—(''Phacochoerus aethiopicus'')<br />forest hogs<br/>—(''[[Hylochoerus]] spp.'') || ''T. suis'' || Africa ||
* ''G. palpalis''
* ''G. fuscipes''
* ''G. morsitans''
* ''G. tachinoides''
* ''G. longipalpis''
* ''G. fusca''
* ''G. tabaniformis''
* ''G. brevipalpis''
* ''G. vanhoofi''
* ''G. austeni''<ref>{{Cite journal |last1=Desquesnes |first1=Marc |last2=Holzmuller |first2=Philippe |last3=Lai |first3=De-Hua |last4=Dargantes |first4=Alan |last5=Lun |first5=Zhao-Rong |last6=Jittaplapong |first6=Sathaporn |date=2013 |title=Trypanosoma evansi and surra: a review and perspectives on origin, history, distribution, taxonomy, morphology, hosts, and pathogenic effects |journal=BioMed Research International |volume=2013 |pages=194176 |doi=10.1155/2013/194176 |doi-access=free |issn=2314-6141 |pmc=3760267 |pmid=24024184}}</ref>
|}

=== In humans ===
{{main article|African trypanosomiasis}}
Human African trypanosomiasis, also called [[African trypanosomiasis|sleeping sickness]], is caused by trypanosomes of the species ''Trypanosoma brucei''. This disease is invariably fatal if left untreated, but can almost always be cured with current medicines if the disease is diagnosed early enough.

Sleeping sickness begins with a tsetse bite leading to an inoculation in the subcutaneous tissue. The infection moves into the [[lymphatic system]], leading to a characteristic swelling of the lymph glands called ''Winterbottom's sign''.<ref>{{Cite web|url=https://sc.edu/study/colleges_schools/medicine/education/basic_science_departments/pathology_microbiology_and_immunology/index.php|title=Pathology, Microbiology and Immunology - School of Medicine {{pipe}} University of South Carolina|website=Sc.edu|access-date=12 November 2020}}</ref> The infection progresses into the blood stream and eventually crosses into the [[central nervous system]] and invades the [[brain]] leading to extreme [[lethargy]] and eventually to [[death]].

The species ''Trypanosoma brucei'', which causes the disease, has often been subdivided into three subspecies that were identified based either on the vertebrate hosts which the strain could infect or on the virulence of the disease in humans. The trypanosomes infectious to animals and not to humans were named ''Trypanosoma brucei brucei''. Strains that infected humans were divided into two subspecies based on their different virulences: ''Trypanosoma brucei gambiense'' was thought to have a slower onset and ''Trypanosoma brucei rhodesiense'' refers to strains with a more rapid, virulent onset. This characterization has always been problematic but was the best that could be done given the knowledge of the time and the tools available for identification. A recent molecular study using [[restriction fragment length polymorphism]] analysis suggests that the three subspecies are [[polyphyletic]],<ref>{{cite journal |author=G. Hide |year=1999 |title=History of Sleeping Sickness in East Africa |journal=[[Clinical Microbiology Reviews]] |volume=12 |issue=1 |pages=112–125|doi=10.1128/CMR.12.1.112 |pmid=9880477 |pmc=88909 |doi-access=free }}</ref> so the elucidation of the strains of ''T. brucei'' infective to humans requires a more complex explanation. [[Procyclin]]s are [[protein]]s developed in the surface coating of trypanosomes whilst in their tsetse fly vector.<ref>{{Cite journal|doi=10.1073/pnas.98.4.1513 |pmid=11171982|title=The surface coat of procyclic Trypanosoma brucei: Programmed expression and proteolytic cleavage of procyclin in the tsetse fly|year=2001|last1=Acosta-Serrano|first1=A. |last2=Vassella|first2=E.|last3=Liniger|first3=M.|last4=Renggli|first4=C. K.|last5=Brun|first5=R. |last6=Roditi|first6=I.|last7=Englund|first7=P. T.|journal=Proceedings of the National Academy of Sciences |volume=98|issue=4|pages=1513–1518 |bibcode=2001PNAS...98.1513A|pmc=29288|doi-access=free}}</ref>{{clarify |reason=This seems unrelated. Are these molecules the sequencing targets that suggested ''brucei'' is not one species? Otherwise why is this mentioned here. |date=October 2020}}

Other forms of human trypanosomiasis also exist but are not transmitted by tsetse. The most notable is American trypanosomiasis, known as [[Chagas disease]], which occurs in [[South America]], caused by ''Trypanosoma cruzi'', and transmitted by certain insects of the [[Reduviidae]], members of the [[Hemiptera]].

===In domestic animals===
{{main article|Animal trypanosomiasis}}
Animal [[trypanosomiasis]], also called ''nagana'' when it occurs in [[cattle|bovine cattle]] or [[horse]]s or ''sura'' when it occurs in domestic [[pig]]s, is caused by several trypanosome species. These [[disease]]s reduce the growth rate, [[milk]] productivity, and strength of [[farm]] animals, generally leading to the eventual [[death]] of the infected animals. Certain species of cattle are called ''[[trypanotolerance|trypanotolerant]]'' because they can survive and grow even when infected with trypanosomes although they also have lower productivity rates when infected.

The course of the disease in animals is similar to the course of [[African trypanosomiasis|sleeping sickness]] in humans.

''Trypanosoma congolense'' and ''Trypanosoma vivax'' are the two most important species infecting bovine cattle in [[sub-Saharan Africa]]. ''Trypanosoma simiae'' causes a virulent disease in [[swine]].

Other forms of animal trypanosomiasis are also known from other areas of the globe, caused by different species of trypanosomes and transmitted without the intervention of the tsetse fly.

The tsetse fly vector ranges mostly in the central part of Africa.

[[Trypanosomiasis]] poses a considerable constraint on livestock agricultural development in tsetse fly-infested areas of sub-Saharan Africa, especially in West and Central Africa. International research conducted by [[ILRI]] in [[Nigeria]], the [[Democratic Republic of the Congo]] and [[Kenya]] has shown that the [[N'Dama]] is the most resistant breed.<ref>{{Cite web |last=Agyemang |first=K. |year=2004 |title=Trypanotolerant livestock in the context of trypanosomiasis intervention strategies |url=https://openknowledge.fao.org/handle/20.500.14283/y5832e |access-date= |series=PAAT Technical and Scientific Series, No. 7. |publisher=FAO |publication-place=Rome}}</ref><ref>{{Cite web|url=https://www.slideshare.net/mobile/ILRI/animal-genetic-resources-characterization-and-conservation-research-in-africa-an-overview|title=Animal genetic resources characterization and conservation research i...|website=Slideshare.net|date=9 January 2012|access-date=12 November 2020}}</ref>

==Control==
The conquest of [[African trypanosomiasis|sleeping sickness]] and [[nagana]] would be of immense benefit to rural development and contribute to poverty alleviation and improved food security in sub-Saharan Africa. Human African trypanosomosis ('''HAT''') and animal African trypanosomosis ('''AAT''') are sufficiently important to make virtually any intervention against these diseases beneficial.<ref>{{Cite book |last1=Shaw |first1=A. P. M. |url=https://openknowledge.fao.org/handle/20.500.14283/y4972e |title=Economic Guidelines for Strategic Planning of Tsetse and Trypanosomiasis Control in West Africa |publisher=FAO |year=2003 |isbn=9789251050064 |series=PAAT Technical and Scientific Series, No. 5. |location=Rome |language=en}}</ref>
[[File:Tsetse-BKF-3.jpg|right|thumb|Tsetse fly from Burkina Faso]]
The disease can be managed by controlling the vector and thus reducing the incidence of the disease by disrupting the transmission cycle. Another tactic to manage the disease is to target the disease directly using surveillance and [[curative care|curative]] or [[prophylactic]] treatments to reduce the number of hosts that carry the disease.

Economic analysis indicates that the cost of managing [[trypanosomosis]] through the elimination of important populations of major tsetse vectors will be covered several times by the benefits of tsetse-free status.<ref name="Budd, L 1999"/> Area-wide interventions against the tsetse and trypanosomosis problem appear more efficient and profitable if sufficiently large areas, with high numbers of cattle, can be covered.

Vector control strategies can aim at either continuous [[Pest control|suppression or eradication]] of target populations. Tsetse fly eradication programmes are complex and logistically demanding activities and usually involve the integration of different control tactics, such as [[trypanocidal]] drugs, [[impregnated treated targets]] (ITT), [[insecticide-treated cattle]] (ITC), [[aerial spraying]] ([[Sequential Aerosol Technique]] - SAT) and in some situations the release of sterile males ([[sterile insect technique]] – SIT). To ensure sustainability of the results, it is critical to apply the control tactics on an area-wide basis, i.e. targeting an entire tsetse population that is preferably [[genetic isolation|genetically isolated]].

===Control techniques===
Many techniques have reduced tsetse populations, with earlier, crude methods recently replaced by methods that are cheaper, more directed, and ecologically better.

====Slaughter of wild animals====
One early technique involved slaughtering all the wild animals tsetse fed on. For example, the island of [[Principe]] off the west coast of Africa was entirely cleared of [[feral]] pigs in the 1930s, which led to the [[Local extinction|extirpation]] of the fly. While the fly eventually re-invaded in the 1950s, the new population of tsetse was free from the disease.<ref name="Headrick-2014">{{cite journal | last=Headrick | first=Daniel R. | editor-last=Büscher | editor-first=Philippe | title=Sleeping Sickness Epidemics and Colonial Responses in East and Central Africa, 1900–1940 | journal=[[PLOS Neglected Tropical Diseases]] | publisher=[[Public Library of Science]] | volume=8 | issue=4 | date=2014-04-24 | issn=1935-2735 | doi=10.1371/journal.pntd.0002772 | page=e2772 | pmid=24763309 | pmc=3998934 | s2cid=18378553| doi-access=free }}</ref><ref name="Costa-et-al-1915">{{cite book |date=30 March 1915 |title=Sleeping sickness - A record of four years' war against it in Principe, Portuguese West Africa |last1=Bruto da Costa |first1=Bernardo Francisco |last2=Sant' Anna |first2=José Firmino |last3=Correia dos Santos |first3=A. |last4=Araujo Alvares |first4=M. G. de |translator-last=Wyllie |translator-first=John Alfred |via=[[Internet Archive]] |url=https://archive.org/details/sleepingsickness00brutrich |access-date=2021-03-20}}</ref><ref name="WHO-tsetse-traps">{{cite web | url=http://www.who.int/tdr/publications/documents/tsetse_traps.pdf | title=STRATEGIC REVIEW OF TRAPS AND TARGETS FOR TSETSE AND AFRICAN TRYPANOSOMIASIS CONTROL|website=who.int | publisher=[[UNICEF]]/[[United Nations Development Programme|UNDP]]/[[World Bank]]/[[World Health Organization|WHO]]/Special Programme for Research and Training in Tropical Diseases |author=F.A.S. Kuzoe |author2=C.J. Schofield | date=2004}}</ref><ref name="McCowen-1913">{{ Cite journal | s2cid=44666631 | title=A Note on Sleeping Sickness in Principe Island and Angola, West Coast of Africa|journal=[[Proceedings of the Royal Society of Medicine]]| year=1913| last1=McCowen| first1=Surgeon| volume=6| issue=Sect Epidemiol State Med| pages=191–194| pmid=19977233| pmc=2006480| doi=10.1177/003591571300601409}}</ref>

====Land clearing====
Another early technique involved [[land clearing|complete removal of brush and woody vegetation from an area]].<ref name="Willett-1963" /> However, the technique was not widely used and has been abandoned.{{cn|date=November 2021}} Tsetse tend to rest on the trunks of trees so removing woody vegetation made the area inhospitable to the flies. Until about 1959 this was done by hand and so was quite time consuming. Glover et al 1959 describes the technique which they call "[[chain clearing]]". Chain clearing drags a chain forward between two heavy vehicles and thereby does the same job much more quickly - but still at some expense.<ref name="Willett-1963">{{cite journal | last=Willett | first=K. C. | title=Trypanosomiasis and the Tsetse Fly Problem in Africa | journal=[[Annual Review of Entomology]] | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=8 | issue=1 | pages=197–214 | year=1963 | issn=0066-4170 | doi=10.1146/annurev.en.08.010163.001213 | pmid=14000804 }}</ref> Preventing regrowth of woody vegetation requires continuous clearing efforts which is even more expensive,<ref name="Willett-1963" /> and only practical where large human populations are present. Also, the clearing of woody vegetation has come to be seen as an environmental problem more than a benefit.{{cn|date=November 2021}}

====Pesticide campaigns====
[[Pesticides]] have been used to control tsetse starting initially during the early part of the twentieth century in localized efforts using the inorganic metal-based pesticides, expanding after the Second World War into massive aerial- and ground-based campaigns with organochlorine pesticides such as [[DDT]] applied as [[aerosol]] sprays at [[Ultra-Low Volume]] rates. Later, more targeted techniques used ''pour-on'' [[pesticide formulation|formulations]] in which advanced organic pesticides were applied directly to the backs of cattle.

====Trapping====
[[Image:TsetseTrap.jpg|right|thumb|Tsetse trap]]
Tsetse populations can be monitored and effectively controlled using simple, inexpensive [[trapping|traps]]. These often use blue cloth, either in sheet or biconical form, since this color attracts the flies. The traps work by channeling the flies into a collection chamber, or by exposing the flies to [[insecticide]] sprayed on the cloth. Early traps mimicked the form of cattle, as tsetse are also attracted to large dark colors like the hides of [[cow]]s and [[Bubalina|buffaloes]]. Some scientists put forward the idea that [[zebra]] have stripes, not as a camouflage in long grass, but because the black and white bands tend to confuse tsetse and prevent attack.<ref>{{cite news|last=Doyle-Burr |first=Nora |title=Scientists unravel mystery of zebra stripes |newspaper=Christian Science Monitor |url=http://www.csmonitor.com/Science/2012/0209/Scientists-unravel-mystery-of-zebra-stripes |access-date=May 15, 2012}}</ref><ref>{{Cite journal| title=Polarotactic tabanids find striped patterns with brightness and/or polarization modulation least attractive: An advantage of zebra stripes| journal=Journal of Experimental Biology| volume=215| issue=5| pages=736–745| year=2012| last1=Egri| first1=A.| last2=Blaho| first2=M.| last3=Kriska| first3=G.| last4=Farkas| first4=R.| last5=Gyurkovszky| first5=M.| last6=Akesson| first6=S.| last7=Horvath| first7=G.| pmid=22323196| doi=10.1242/jeb.065540| doi-access=free}}</ref>

The use of chemicals as attractants to lure tsetse to the traps has been studied extensively in the late 20th century, but this has mostly been of interest to scientists rather than as an economically reasonable solution. Attractants studied have been those tsetse might use to find food, like [[carbon dioxide]], [[octenol]], and [[acetone]]&mdash;which are given off in animals' breath and distributed downwind in an ''odor plume.'' Synthetic versions of these chemicals can create artificial odor plumes. A cheaper approach is to place cattle [[urine]] in a half gourd near the trap. For large trapping efforts, additional traps are generally cheaper than expensive artificial attractants.

A special trapping method is applied in [[Ethiopia]], where the BioFarm Consortium ([[ICIPE]], BioVision Foundation, BEA, Helvetas, [[DLCO-EA]], Praxis Ethiopia) applies the traps in a [[sustainable agriculture]] and [[rural development]] context (SARD). The traps are just the entry point, followed by improved farming, human health and marketing inputs. This method is in the final stage of testing (as of 2006).

====Sterile insect technique====
The [[sterile insect technique]] ('''SIT''') is a form of pest control that uses [[ionizing radiation]] ([[gamma ray]] or [[X-ray]]) to sterilize male flies that are mass-produced in special rearing facilities. The sterile males are released systematically from the ground or by air in tsetse-infested areas, where they mate with wild females, which do not produce offspring. As a result, this technique can eventually eradicate populations of wild flies. SIT is among the most [[environmentally friendly]] control tactics available, and is usually applied as the final component of an integrated campaign. It has been used to subdue the populations of many other fly species including the medfly, ''[[Ceratitis capitata]]''.

The sustainable removal of the tsetse fly is in many cases the most cost-effective way of dealing with the T&T problem resulting in major economic benefits for subsistence farmers in rural areas. Insecticide-based methods are normally very ineffective in removing the last remnants of tsetse populations, while, on the contrary, sterile males are very effective in finding and mating the last remaining females. Therefore, the integration of the SIT as the last component of an area-wide integrated approach is essential in many situations to achieve complete eradication of the different tsetse populations, particularly in areas of more dense vegetation.

A project that was implemented from 1994 to 1997 on the Island of [[Unguja]], [[Zanzibar]] (United Republic of [[Tanzania]]), demonstrated that, after suppression of the tsetse population with insecticides, SIT completely removed the ''[[Glossina austeni]]'' Newstead population from the Island.<ref name="Vreysen-et-al-2000">{{cite journal | last1=Vreysen | first1=Marc J. B. | last2=Saleh | first2=Khalfan M. | last3=Ali | first3=Mashavu Y. | last4=Abdulla | first4=Abdulla M. | last5=Zhu | first5=Zeng-Rong | last6=Juma | first6=Kassim G. | last7=Dyck | first7=V. Arnold | last8=Msangi | first8=Atway R. | last9=Mkonyi | first9=Paul A. | last10=Feldmann | first10=H. Udo | title=''Glossina austeni'' (Diptera: Glossinidae) Eradicated on the Island of Unguja, Zanzibar, Using the Sterile Insect Technique | journal=[[Journal of Economic Entomology]] | publisher=[[Oxford University Press]] (OUP) | volume=93 | issue=1 | date=2000 | issn=0022-0493 | pmid=14658522 | doi=10.1603/0022-0493-93.1.123 | pages=123–135 | s2cid=41188926| doi-access=free }}</ref><ref name="Caragata-et-al-2020">{{cite journal | last1=Caragata | first1=E.P. | last2=Dong | first2=S. | last3=Dong | first3=Y. | last4=Simões | first4=M.L. | last5=Tikhe | first5=C.V. | last6=Dimopoulos | first6=G. | title=Prospects and Pitfalls: Next-Generation Tools to Control Mosquito-Transmitted Disease | journal=[[Annual Review of Microbiology]] | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=74 | issue=1 | date=2020-09-08 | issn=0066-4227 | doi=10.1146/annurev-micro-011320-025557 | pages=455–475| pmid=32905752 | s2cid=221625690 | doi-access=free }}</ref> This was carried out without any understanding of the [[population genetics]] of ''G. a.'', but future SIT efforts can benefit from such preparation. Population genetics would help to select the ''Glossina'' population to be deployed for similarity to the target population.<ref name="Krafsur-Ouma-2021">{{cite book | editor1-last=Dyck | editor1-first=Victor | editor2-last=Hendrichs | editor2-first=J. | editor3-last=Robinson | editor3-first=A. S. | title=Sterile Insect Technique Principles And Practice In Area-Wide Integrated Pest Management | publisher=[[CRC Press]] | year=2021 | isbn=978-1-000-37776-7 | oclc=1227700317 | language=en | chapter=4.1 - Role of Population Genetics in the Sterile Insect Technique | first1=E. S. | last1=Krafsur | first2=J. O. | last2=Ouma | pages=529–548/xv+1200}} {{ISBN|978-0-367-47434-8}} {{ISBN|978-1-003-03557-2}}</ref> The eradication of the tsetse fly from Unguja Island in 1997 was followed by the disappearance of the AAT which enabled farmers to integrate livestock keeping with cropping in areas where this had been impossible before. The increased livestock and crop productivity and the possibility of using animals for transport and traction significantly contributed to an increase in the quality of people's lives.<ref>{{cite journal |vauthors=Tambi EN, Maina OW, Mukhebi AW, Randolph TF |date=1999 |title=Economic impact assessment of rinderpest control in Africa |journal=Revue Scientifique et Technique de l'OIE |trans-journal=OIE Scientific and Technical Review |volume=18 |issue=2 |pages=458–477|doi=10.20506/rst.18.2.1164 |pmid=10472679 |doi-access=free }}</ref><ref>{{cite report |last=Mdoe |first=N. S. Y. |date=2003 |title=Livestock and agriculture development in Zanzibar, post-tsetse eradication: a follow-up socio-economic study |publisher=Report prepared for the International Atomic Energy Agency. IAEA |place=Vienna, Austria}}</ref> Surveys in 1999, 2002, 2014, and 2015 have confirmed this success - continued absence of tsetse and [[nagana]] on the island.<ref name="Zanzibar-20-years">{{cite web | title=Tsetse Free for 20 Years Thanks to a Nuclear Technique: The Island of Unguja, Zanzibar | website=[[International Atomic Energy Agency|IAEA]] (International Atomic Energy Agency) | date=2016-10-24 | url=https://www.iaea.org/newscenter/news/tsetse-free-for-20-years-thanks-to-a-nuclear-technique-the-island-of-unguja-zanzibar | access-date=2021-11-17}}</ref>

In the [[Niayes]] region of [[Senegal]], a coastal area close to [[Dakar]], livestock keeping was difficult due to the presence of a population of ''[[Glossina palpalis gambiensis]]''. Feasibility studies indicated that the fly population was confined to very fragmented habitats and a population genetics study indicated that the population was genetically isolated from the main tsetse belt in the south eastern part of Senegal. After completion of the feasibility studies (2006–2010), an area-wide integrated eradication campaign that included an SIT component was started in 2011, and by 2015, the Niayes region had become almost tsetse fly free. This has allowed a change of [[cattle breed]]s from lower producing [[trypanotolerant]] breeds to higher-producing foreign breeds.<ref>{{cite web |title=The Tsetse Fly Eradication Project in Senegal Wins Award for Best Sustainable Development Practices |date=23 July 2015 |url=https://www.iaea.org/newscenter/news/tsetse-fly-eradication-project-senegal-wins-award-best-sustainable-development-practices|access-date=12 November 2020|website=Iaea.org}}</ref><ref>{{cite news |last=Paquette |first=Danielle |date=2019-05-31 |title=A U.S.-funded nuclear project to zap a killer fly into extinction is saving West Africa's cows |url=https://www.washingtonpost.com/world/africa/a-us-funded-nuclear-project-to-zap-a-killer-fly-into-extinction-is-saving-west-africas-cows/2019/05/31/12f92626-7713-11e9-a7bf-c8a43b84ee31_story.html |newspaper=[[The Washington Post]] |access-date=2019-06-01}}</ref>

The entire target area (Block 1, 2 and 3) has a total surface of {{convert|1000|km2|sqmi}}, and the first block (northern part) can be considered free of tsetse, as intensive monitoring has failed to detect since 2012 a single wild tsetse fly. The prevalence of AAT has decreased from 40 to 50% before the project started to less than 10% to date in blocks 1 and 2. Although insecticides are being used for fly suppression, they are applied for short periods on traps, nets and livestock, and are not spread into the environment. After the suppression activities are completed, no more insecticide is applied in the area. The removal of trypanosomosis will eliminate the need for constant prophylactic treatments of the cattle with trypanocidal drugs, therefore reducing [[residue (chemistry)|residue]]s of these drugs in the [[Feces|dung]], meat and milk.

The main beneficiaries of the project are the many small holder farmers, the larger commercial farms and the consumers of meat and milk. According to a socio-economic survey and benefit cost analysis,<ref>{{cite journal |last1=Bouyer |first1=F |last2=Seck |first2=MT |last3=Dicko |first3=AH |last4=Sall |first4=B |last5=Lo |first5=M |last6=Vreysen |first6=MJB |last7=Chia |first7=E |last8=Bouyer |first8=J |last9=Wane |first9=A |display-authors=5 |year=2014 |title=Ex-ante Benefit-Cost Analysis of the Elimination of a Glossina palpalis gambiensis Population in the Niayes of Senegal |journal=PLOS Negl Trop Dis |volume=8 |issue=8| page=e3112 |doi=10.1371/journal.pntd.0003112 | pmid=25144776 |pmc=4140673 |doi-access=free}}</ref> after eradication of the tsetse farmers will be able to replace their local breeds with improved breeds and increase their annual income by €2.8 million. In addition, it is expected that the number of cattle will be reduced by 45%, which will result in reduced environmental impacts.

==Societal impact==
{{see also|African trypanosomiasis#History}}

In the literature of [[environmental determinism]], the tsetse has been linked to difficulties during early [[state formation]] for areas where the fly is prevalent. A 2012 study used population growth models, physiological data, and ethnographic data to examine pre-colonial agricultural practices and isolate the effects of the fly. A "tsetse suitability index" was developed from insect population growth, climate and geospatial data to simulate the fly's population steady state. An increase in the tsetse suitability index was associated with a statistically significant weakening of the agriculture, levels of urbanization, institutions and subsistence strategies. Results suggest that the tsetse decimated livestock populations, forcing early states to rely on slave labor to clear land for farming, and preventing farmers from taking advantage of natural animal fertilizers to increase crop production. These long-term effects may have kept population density low and discouraged cooperation between small-scale communities, thus preventing stronger nations from forming.

The authors {{who|date=September 2022}} also suggest that under a lower burden of tsetse, Africa would have developed differently. Agriculture (measured by the usage of large domesticated animals, intensive agriculture, plow use and female participation rate in agriculture) as well as institutions (measured by the appearance of indigenous slavery and levels of centralization) would have been more like those found in Eurasia. Qualitative support for this claim comes from archaeological findings; e.g., [[Great Zimbabwe]] is located in the African highlands where the fly does not occur, and represented the largest and technically most advanced precolonial structure in Southern sub-Sahara Africa.<ref>{{cite journal |last1=Alsan|first1=Marcella|title=The Effect of the Tsetse fly on African Development |journal=American Economic Review|date=January 2015|volume=105|issue=105|pages=382–410 |doi=10.1257/aer.20130604 |url=http://healthpolicy.fsi.stanford.edu/sites/default/files/tsetse.pdf|access-date=2019-09-05 |archive-date=2015-06-20|archive-url=https://web.archive.org/web/20150620173603/http://healthpolicy.fsi.stanford.edu/sites/default/files/tsetse.pdf}}</ref>

Other authors are more skeptical that the tsetse fly had such an immense influence on African development. One conventional argument is that the tsetse fly made it difficult to use draught animals. Hence, wheeled forms of transportations were not used as well. While this is certainly true for areas with high densities of the fly, similar cases outside tsetse-suitable areas exist. While the fly definitely had a relevant influence on the adoption of new technologies in Africa, it has been contended that it does not represent the single root cause.<ref>{{Cite journal |last1=Chaves |first1=Isaías |last2=Engerman |first2=Stanley |last3=Robinson |first3=James |date=November 2013 |title=Reinventing the Wheel: The Economic Benefits of Wheeled Transportation in Early British Colonial West Africa |journal=NBER Working Paper Series |id=Working Paper 19673 |doi=10.3386/w19673 |s2cid=153184179 |doi-access=free}}</ref>

===History===
According to an article in the ''[[New Scientist]]'', the depopulated and apparently primevally wild Africa seen in wildlife documentary films was formed in the 19th century by disease, a combination of [[rinderpest]] and the tsetse fly. Rinderpest is believed to have originated in Asia, later spreading through the transport of cattle.<ref name="nytimes">{{cite news |title=Virus Deadly in Livestock Is No More, U.N. Declares |author=Donald G. McNeil Jr. |author-link=Donald McNeil, Jr. |work=[[The New York Times]] |date=15 October 2010 |url=https://www.nytimes.com/2010/10/16/science/16pest.html |access-date=15 October 2010}}</ref> In 1887, the rinderpest virus was accidentally imported in livestock brought by an Italian expeditionary force to Eritrea. It spread rapidly, reaching Ethiopia by 1888, the Atlantic coast by 1892 and South Africa by 1897. Rinderpest, a cattle plague from central Asia, killed over 90% of the cattle of the pastoral peoples such as the [[Maasai people|Masai]] of east Africa. In South Africa, with no native [[immunity (medical)|immunity]], most of the population – some 5.5 million domestic cattle – died. Pastoralists and farmers were left with no animals – their source of income – and farmers were deprived of their working animals for ploughing and irrigation. The pandemic coincided with a period of drought, causing widespread famine. The starving human populations died of smallpox, cholera, and typhoid, as well as African Sleeping Sickness and other endemic diseases. It is estimated that two-thirds of the Masai died in 1891.<ref name=Pearce2000>{{cite journal |last1=Pearce |first1=Fred |date=12 August 2000 |title=Inventing Africa |journal=New Scientist |volume=167 |issue=2251 |page=30 |url=https://www.faculty.umb.edu/pjt/pearce00.pdf }}</ref>{{Additional citation needed|date=December 2020}}

The land was left emptied of its cattle and its people, enabling the colonial powers Germany and Britain to take over Tanzania and Kenya with little effort. With greatly reduced grazing, grassland turned rapidly to bush. The closely cropped grass sward was replaced in a few years by woody grassland and thornbush, ideal habitat for tsetse flies. Wild mammal populations increased rapidly, accompanied by the tsetse fly. [[Highland]] regions of east Africa which had been free of tsetse fly were colonised by the pest, accompanied by sleeping sickness, until then unknown in the area. Millions of people died of the disease in the early 20th century.<ref name=Pearce2000/>{{Additional citation needed|date=December 2020}}

[[File:Masai Giraffe, Serengeti National Park, Tanzania (2010).jpg|thumb|[[Serengeti National Park]], Tanzania]]

The areas occupied by the tsetse fly were largely barred to [[animal husbandry]]. Sleeping sickness was dubbed "the best game warden in Africa" by conservationists{{citation needed | reason=Widely quoted but never attributed |date=October 2020}}, who assumed that the land, empty of people and full of game animals, had always been like that. [[Julian Huxley]] of the [[World Wildlife Fund]] called the plains of east Africa "a surviving sector of the rich natural world as it was before the rise of modern man".<ref name=Pearce2000/>{{Additional citation needed|date=December 2020}} They created numerous large reserves for hunting [[safari]]s. In 1909 the newly retired president [[Theodore Roosevelt]] went on a safari that brought over 10,000 animal carcasses to America. Later, much of the land was turned over to nature reserves and [[national parks]] such as the [[Serengeti]], [[Masai Mara]], [[Kruger Park|Kruger]] and [[Okavango Delta]]. The result, across eastern and southern Africa, is a modern landscape of manmade ecosystems: farmland and pastoral land largely free of bush and tsetse fly; and bush controlled by the tsetse fly.<ref name=Pearce2000/>{{Additional citation needed|date=December 2020}}

Although the colonial powers saw the disease as a threat to their interests, and acted accordingly to bring transmission almost to a halt in the 1960s,<ref name="naganamanagement" />{{rp|page=0174}} this improved situation led to a laxity of surveillance and management by the newly independent governments covering the same areas - and a resurgence that became a crisis again in the 1990s.<ref name="naganamanagement" />{{rp|page=0174}}<ref name="naganamanagement">{{cite journal | last1=Simarro | first1=Pere P | last2=Jannin | first2=Jean | last3=Cattand | first3=Pierre | title=Eliminating Human African Trypanosomiasis: Where Do We Stand and What Comes Next? | journal=[[PLOS Medicine]] | publisher=[[Public Library of Science]] (PLoS) | volume=5 | issue=2 | date=2008-02-26 | issn=1549-1676 | doi=10.1371/journal.pmed.0050055 | page=e55 | pmid=18303943 | pmc=2253612 | s2cid=17608648| doi-access=free }}</ref>{{rp|page=0175}}

===Current situation===

Tsetse flies are regarded as a major cause of rural poverty in [[sub-Saharan Africa]]<ref name="Vreysen-et-al-2013" /> because they prevent mixed farming. The land infested with tsetse flies is often cultivated by people using hoes rather than more efficient draught animals because ''[[nagana]]'', the disease transmitted by tsetse, weakens and often kills these animals. Cattle that do survive produce little milk, pregnant cows often abort their calves, and manure is not available to fertilize the worn-out soils.
[[File:Tsetse-BKF-2.jpg|right|thumb|Tsetse fly from Burkina Faso]]

The disease ''nagana'' or African [[animal trypanosomiasis]] (AAT) causes gradual health decline in infected livestock, reduces milk and meat production, and increases abortion rates. Animals eventually succumb to the disease - annual cattle deaths caused by trypanosomiasis are estimated at 3 million{{citation needed|date=April 2021}}, reducing annual cattle production value by US$600m-US$1.2b.<ref name="Vreysen-et-al-2013" /> This has an enormous impact on the livelihood of farmers who live in tsetse-infested areas, as infected animals cannot be used to plough the land, and keeping cattle is only feasible when the animals are kept under constant [[prophylactic]] treatment with [[trypanocidal agent|trypanocidal drugs]], often with associated problems of [[trypanocide resistance|drug resistance]], counterfeited drugs, and suboptimal dosage. The overall annual direct lost potential in livestock and crop production was estimated at US$4.5 billion<ref name="Budd, L 1999">Budd, L. 1999. DFID-funded tsetse and trypanosome research and development since 1980. Vol. 2. Economic analysis. Aylesford, UK, DFID Livestock Production, Animal Health and Natural Resources Systems Research Programmes</ref><ref>DFID. 2001. Trypanosomiasis, tsetse and Africa. The year 2001 report. Aylesford, UK, Department for International Development.</ref>-US$4.75b.<ref name="Vreysen-et-al-2013" />

The tsetse fly lives in nearly {{convert|10000000|sqkm|-6}} in sub-Saharan Africa<ref name="Vreysen-et-al-2013" /> (mostly wet tropical forest) and many parts of this large area is fertile land that is left uncultivated—a so-called [[green desert]] not used by humans and cattle. Most of the 38 countries<ref name="Vreysen-et-al-2013"/> infested with tsetse are poor, debt-ridden and underdeveloped. Of the 38<ref name="Vreysen-et-al-2013" /> tsetse-infested countries, 32 are [https://www.fao.org/countryprofiles/lifdc/en/ low-income, food-deficit countries], 29 are [[least developed countries]], and 30{{citation needed|date=April 2021}} or 34<ref name="Vreysen-et-al-2013" /> are among the 40 most [[heavily indebted poor countries]]. Eradicating the tsetse and trypanosomiasis (T&T) problem would allow rural Africans to use these areas for [[animal husbandry]] or the cultivation of crops and hence increase food production. Only 45 million cattle, of 172 million present in sub-Saharan Africa, are kept in tsetse-infested areas but are often forced into fragile ecosystems like highlands or the [[semiarid]] [[Sahel]] zone, which increases overgrazing and overuse of land for food production.

In addition to this direct impact, the presence of tsetse and trypanosomiasis discourages the use of more productive exotic and cross-bred cattle, depresses the growth and affects the distribution of livestock populations, reduces the potential opportunities for livestock and crop production (mixed farming) through less draught power to cultivate land and less manure to fertilize (in an environment-friendly way) soils for better crop production, and affects human settlements (people tend to avoid areas with tsetse flies).

Tsetse flies transmit a similar disease to humans, called [[African trypanosomiasis]], human African trypanosomiasis (HAT) or sleeping sickness. An estimated 60<ref name="Vreysen-et-al-2013" />-70<ref name="Simarro-et-al-2012">{{cite journal | title=Simarro PP, Cecchi G, Franco JR, Paone M, Diarra A, Ruiz-Postigo JA, et al. (2012). Estimating and Mapping the Population at Risk of Sleeping Sickness. PLoS Negl Trop Dis 6(10): e1859.| year=2012| doi=10.1371/journal.pntd.0001859| pmid=23145192| doi-access=free| last1=Simarro| first1=P. P.| last2=Cecchi| first2=G.| last3=Franco| first3=J. R.| last4=Paone| first4=M.| last5=Diarra| first5=A.| last6=Ruiz-Postigo| first6=J. A.| last7=Fèvre| first7=E. M.| last8=Mattioli| first8=R. C.| last9=Jannin| first9=J. G.| journal=PLOS Neglected Tropical Diseases| volume=6| issue=10| pages=e1859| pmc=3493382}}</ref> million people in 20 countries are at different levels of risk and only 3-4 million people are covered by active surveillance.<ref name="Vreysen-et-al-2013" /> The [[DALY]] index (disability-adjusted life years), an indicator to quantify the burden of disease, includes the impact of both the duration of life lost due to premature death and the duration of life lived with a disability. The annual burden of sleeping sickness is estimated at 2 million DALYs. Since the disease tends to affect economically active adults, the total cost to a family with a patient is about 25% of a year's income.<ref>Shaw, A.P.M., 2004. Economics of African trypanosomiasis. In The Trypanosomiases (eds. I. Maudlin, P.H. Holmes & M.A. Miles) CABI Publishing, 2004, pp. 369-402</ref>

==History of study==
{{expand section|date=December 2021}}
In East Africa, [[Charles Francis Massy Swynnerton|C. F. M. Swynnerton]] played a large role in the first half of the 20th century. Swynnerton did much of the earliest tsetse ecology research.<ref>''Clement Gillman, 1882-1946: Biographical Notes on a Pioneer East African Geographer''. [[East African Geographical Review]]. Makerere:{{nbsp}}[[Makerere University]]. Hoyle, Brian S. pp.{{nbsp}}1{{endash}}16. {{ISSN|1937-6812}}. {{eISSN|2163-2642}}. {{LCCN|67038577}}. {{OCLC|51782062}}.</ref> For this [[Ernest Edward Austen|E. E. Austen]] named a [[patronymic taxon]] for him, ''[[Glossina swynnertoni|G. swynnertoni]]'' in 1922.<ref name="Austen-1922" />

==Resistance to trypanosomes==

Tsetse flies have an arsenal of immune defenses to resist each stage of the trypanosome infectious cycle, and thus are relatively refractory to trypanosome infection.<ref name="pmid26027775">{{cite journal |vauthors=Gibson W |title=Liaisons dangereuses: sexual recombination among pathogenic trypanosomes |journal=Res. Microbiol. |volume=166 |issue=6 |pages=459–66 |year=2015 |pmid=26027775 |doi=10.1016/j.resmic.2015.05.005 |url=https://research-information.bristol.ac.uk/files/130784363/Liaisons_dangereuses_acceptedMS.pdf|hdl=1983/1ecb5cba-da25-4e93-a3cb-b00a0477cb23 |s2cid=9594154 |hdl-access=free }}</ref> Among the host flies' defenses is the production of [[hydrogen peroxide]],<ref name="pmid14563366">{{cite journal |vauthors=Hao Z, Kasumba I, Aksoy S |title=Proventriculus (cardia) plays a crucial role in immunity in tsetse fly (Diptera: Glossinidiae) |journal=Insect Biochem. Mol. Biol. |volume=33 |issue=11 |pages=1155–64 |year=2003 |pmid=14563366 |doi= 10.1016/j.ibmb.2003.07.001}}</ref> a [[reactive oxygen species]] that damages [[DNA]]. These defenses limit the population of infected flies.

==See also==
* [[David Bruce (microbiologist)]]
* [[Geoffrey Douglas Hale Carpenter|G.D. Hale Carpenter]] joined the [[London School of Hygiene and Tropical Medicine]], and took the [[Doctorate in Medicine|DM]] in 1913 with a dissertation on the tsetse fly (''[[Glossina palpalis]]'') and [[African trypanosomiasis|sleeping sickness]]. He published: [https://archive.org/details/naturalistonlake00carp ''A Naturalist on Lake Victoria, with an Account of Sleeping Sickness and the Tse-tse Fly''; 1920. T.F. Unwin Ltd, London; Biodiversity Archive]
* [[Muriel Robertson]], who conducted early 20th century research on the insect
* [[Use of DNA in forensic entomology]]
* [[Horses in Botswana]]

== References ==
{{Reflist|30em}}

==Further reading==
*{{cite magazine|title=Tsetse|first=George|last=Gerster|magazine=[[National Geographic (magazine)|National Geographic]]|pages=814–833|volume=170|issue=6|date=December 1986|issn=0027-9358|oclc=643483454}}
*{{cite journal | last1=Gooding | first1=R.H. | last2=Krafsur | first2=E.S. | title=Tsetse genetics: Contributions to Biology, Systematics, and Control of Tsetse Flies | journal=[[Annual Review of Entomology]] | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=50 | issue=1 | year=2005 | issn=0066-4170 | doi=10.1146/annurev.ento.50.071803.130443 | pages=101–123 | pmid=15355235 | s2cid=22834246| pmc=1462949 }}

=== Textbooks ===
* Buxton, P. (1955). ''The Natural History of Tsetse Flies: An Account of the Biology of the Genus Glossina (Diptera)''. London, UK: [[H. K. Lewis & Co. Ltd.]]
* Ford, J. (1971). ''The Role of the Trypanosomiases in African Ecology''. Oxford, UK: Clarendon Press.
* Glasgow, J. (1963). ''The Distribution and Abundance of Tsetse''. International Series of Monographs on Pure and Applied Biology, No. 20. Oxford, UK: Pergamon Press.
* Leak, S. (1998). ''Tsetse Biology and Ecology: Their role in the Epidemiology and Control of Trypanosomiasis''. New York: CABI Publishing. [https://web.archive.org/web/20110613040449/http://www.cabi-publishing.org/bookshop/BookDisplay.asp?SubjectArea=Hum&Subject=Public+Health+and+Communicable+Diseases&PID=1406 book site]
* Maudlin, I., Holmes, P. H., and Miles, M. A. (2004). ''The Trypanosomiases''. CAB International.
* McKelvey, J., Jr. (1973). ''Man Against Tsetse: Struggle for Africa''. Ithaca, NY: Cornell University Press.
* Mulligan, H. & Potts, W. (1970). ''The African Trypanosomiases''. London: George Allen and Unwin, Ltd.

==External links==
{{Commons category|Glossina}}
{{Wikispecies|Glossina}}
*[https://www.tsetse.org Programmes and information to assist in the planning and implementation of tsetse control operations]
*[https://www.fao.org/paat Programme Against African Trypanosomiasis] {{Webarchive|url=https://web.archive.org/web/20210415143408/http://www.fao.org/ag/paat.html |date=15 April 2021 }}
*[https://web.archive.org/web/20050409122056/http://www.africa-union.org/Structure_of_the_Commission/depPattec.htm PAN AFRICAN TSETSE AND TRYPANOSOMIASIS ERADICATION CAMPAIGN (PATTEC)]
*[https://web.archive.org/web/20120227040712/http://www.mosquitocatalog.org/files/pdfs/045050-0.pdf ''Tsetse in the Transvaal and Surrounding Territories - An Historical Review'']—[[Claude Fuller (entomologist)|Claude Fuller]] (Division of Entomology, 1923)
*[https://web.archive.org/web/20070606225734/http://www.lshtm.ac.uk/pmbu/lttrn/ Leverhulme Trust Tsetse Research Network (LTTRN)]
*[https://archive.today/20130104081354/http://www.nzitrap.com/index.htm BITING FLIES - The NZI Trap]
*[https://web.archive.org/web/20090301142911/http://ergodd.zoo.ox.ac.uk/livatl2/tsetse.htm Distribution maps]
*{{cite web | title=The vector (tsetse fly) | website=[[World Health Organization]] | date=2016-08-05 | url=http://www.who.int/trypanosomiasis_african/disease/vector/en/ | archive-url=https://web.archive.org/web/20160929202859/http://www.who.int/trypanosomiasis_african/disease/vector/en/ | archive-date=September 29, 2016 | access-date=2020-12-04}}
*[http://www.who.int/tdr/publications/documents/tsetse_traps.pdf STRATEGIC REVIEW OF TRAPS AND TARGETS FOR TSETSE AND AFRICAN TRYPANOSOMIASIS CONTROL - Training in Tropical Diseases]
*{{cite web | title=Insect of the Month (October): Tsetse fly, ''Glossina morsitans'' | website=[[International Centre of Insect Physiology and Ecology|icipe]] (International Centre of Insect Physiology and Ecology) | url=https://www.icipe.org/news/insect-month-october-tsetse-fly-glossina-morsitans | access-date=2021-10-09}}

{{Diptera|2}}

{{Insects in culture}}
{{Taxonbar|from=Q205256}}
{{Authority control}}

{{DEFAULTSORT:Tsetse Fly}}
[[Category:Diptera of Africa]]
[[Category:Insect vectors of human pathogens]]
[[Category:Extant Eocene first appearances]]
[[Category:Insects in culture]]
[[Category:Flies and humans]]
[[Category:Hippoboscoidea]]