Editing Tsetse fly (section)

==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>