Editing Toxoplasmosis (section)

== Epidemiology ==
''T. gondii'' infections occur throughout the world, although infection rates differ significantly by country.<ref name="Pappas_2009">{{cite journal |vauthors=Pappas G, Roussos N, Falagas ME | title = Toxoplasmosis snapshots: global status of ''Toxoplasma gondii'' seroprevalence and implications for pregnancy and congenital toxoplasmosis | journal = International Journal for Parasitology | volume = 39 | issue = 12 | pages = 1385–94 | date = October 2009 | pmid = 19433092 | doi = 10.1016/j.ijpara.2009.04.003 }}</ref> For women of childbearing age, a survey of 99 studies within 44 countries found the areas of highest prevalence are within [[Latin America]] (about 50–80%), parts of [[Eastern Europe|Eastern]] and [[Central Europe]] (about 20–60%), the [[Middle East]] (about 30–50%), parts of [[Southeast Asia]] (about 20–60%), and parts of [[Africa]] (about 20–55%).<ref name="Pappas_2009" />

In the United States, data from the [[National Health and Nutrition Examination Survey]] (NHANES) from 1999 to 2004 found 9.0% of US-born persons 12–49 years of age were [[seropositive]] for [[IgG]] [[antibodies]] against ''T.&nbsp;gondii'', down from 14.1% as measured in the NHANES 1988–1994.<ref name="Jones_2007">{{cite journal |vauthors=Jones JL, Kruszon-Moran D, Sanders-Lewis K, Wilson M | title = ''Toxoplasma gondii'' infection in the United States, 1999 2004, decline from the prior decade | journal = American Journal of Tropical Medicine and Hygiene | volume = 77 | issue = 3 | pages = 405–10 | date = September 2007 | pmid = 17827351 | doi = 10.4269/ajtmh.2007.77.405 | doi-access = free }}</ref> In the 1999–2004 survey, 7.7% of US-born and 28.1% of foreign-born women 15–44 years of age were ''T.&nbsp;gondii'' seropositive.<ref name="Jones_2007" /> A trend of decreasing [[seroprevalence]] has been observed by numerous studies in the United States and many European countries.<ref name="Pappas_2009" /> ''Toxoplasma gondii'' is considered the second leading cause of [[Foodborne illness|foodborne]]-related deaths and the fourth leading cause of foodborne-related hospitalizations in the United States.<ref name="Scallan">{{cite journal|last1=Scallan|first1=Elaine|last2=Hoekstra|first2=Robert|last3=Angulo|first3=Frederick|last4=Tauxe|first4=Robert|last5=Widdowson|first5=Marc-Alain|last6=Roy|first6=Sharon|last7=Jones|first7=Jeffery|last8=Griffin|first8=Patricia|title=Foodborne Illness Acquired in the United States - Major Pathogens|journal=Emerging Infectious Diseases|date=January 2011|volume=17|issue=1|pages=7–15|doi=10.3201/eid1701.P11101|pmid=21192848|pmc=3375761}}</ref>

The protist responsible for toxoplasmosis is ''T.&nbsp;gondii''. Three major types of ''T.&nbsp;gondii'' are responsible for the patterns of toxoplasmosis throughout the world, named types I, II, and III. These three types of ''T.&nbsp;gondii'' have differing effects on certain hosts, mainly mice and humans due to their variation in genotypes.<ref name="Dalimi">{{cite journal |last1=Dalimi |first1=A. |last2=Abdoli |first2=A. |title=Latent toxoplasmosis and human |journal=Iranian Journal of Parasitology |date=2012 |volume=7 |issue=1 |pages=1–17 |pmid=23133466 |pmc=3488815 }}</ref>
* Type I: virulent in mice and humans, seen in [[people with AIDS]].
* Type II: non-virulent in mice, virulent in humans (mostly Europe and North America), seen in people with AIDS.
* Type III: non-virulent in mice, virulent mainly in animals but seen to a lesser degree in humans as well.

Current [[serotyping]] techniques can only separate type I or III from type II parasites.<ref name=Sibley2009>{{cite journal|author1=Sibley LD|author2=Khan A|author3=Ajioka JW|author4=Rosenthal BM|title=Genetic diversity of ''Toxoplasma gondii'' in animals and humans|journal=Philosophical Transactions of the Royal Society B: Biological Sciences|date=2009|volume=364|issue=1530|pages=2749–2761|doi=10.1098/rstb.2009.0087|pmid=19687043|pmc=2865090}}</ref>

Because the parasite poses a particular threat to fetuses when it is contracted during pregnancy,<ref name=CDCPregnant>{{cite web|title=CDC: Parasites – Toxoplasmosis (Toxoplasma infection) – Pregnant Women|url=https://www.cdc.gov/parasites/toxoplasmosis/gen_info/pregnant.html|access-date=13 March 2013|url-status=live|archive-url=https://web.archive.org/web/20130307191447/http://www.cdc.gov/parasites/toxoplasmosis/gen_info/pregnant.html|archive-date=7 March 2013}}</ref> much of the global [[epidemiological]] data regarding ''T.&nbsp;gondii'' comes from seropositivity tests in women of childbearing age. Seropositivity tests look for the presence of antibodies against ''T.&nbsp;gondii'' in blood, so while seropositivity guarantees one has been exposed to the parasite, it does not necessarily guarantee one is chronically infected.<ref name=Dubey_1998_Rats>{{cite journal |vauthors=Dubey JP, Frenkel JK | title = Toxoplasmosis of rats: a review, with considerations of their value as an animal model and their possible role in epidemiology | journal = Veterinary Parasitology | volume = 77 | issue = 1 | pages = 1–32 | date = May 1998 | pmid = 9652380 | doi = 10.1016/S0304-4017(97)00227-6 | url = https://zenodo.org/record/1260015 }}</ref>