Globalization and the population structure of Toxoplasma gondii

Abstract

Toxoplasma gondii is a protozoan parasite that infects nearly all mammal and bird species worldwide. Usually asymptomatic, toxoplasmosis can be severe and even fatal to many hosts, including people. Elucidating the contribution of genetic variation among parasites to patterns of disease transmission and manifestations has been the goal of many studies. Focusing on the geographic component of this variation, we show that most genotypes are locale-specific, but some are found across continents and are closely related to each other, indicating a recent radiation of a pandemic genotype. Furthermore, we show that the geographic structure of T. gondii is extraordinary in having one population that is found in all continents except South America, whereas other populations are generally confined to South America, and yet another population is found worldwide. Our evidence suggests that South American and Eurasian populations have evolved separately until recently, when ships populated by rats, mice, and cats provided T. gondii with unprecedented migration opportunities, probably during the transatlantic slave trade. Our results explain several enigmatic features of the population structure of T. gondii and demonstrate how pervasive, prompt, and elusive the impact of human globalization is on nature.evolutionary history ͉ migration ͉ pandemic genotype ͉ protozoan parasite ͉ trade

Genetic characterisation of Toxoplasma gondii in wildlife from North America revealed widespread and high prevalence of the fourth clonal type

“…Historically, T. gondii was considered to be clonal with low genetic diversity (Dardé et al, 1992;Howe and Sibley, 1995 (Lehmann et al, 2006;Dubey et al, 2002Dubey et al, , 2007a. Humans can become infected post-natally by ingesting tissue cysts from undercooked meat, or by consuming food or drink contaminated with oocysts.…”

Prevalence of Toxoplasma infection in veterinary laboratory sciences students comparing to ordinary people: a case–control study

“…There are some factors which may vary the prevalence of the infection in different regions such as environmental condition, cultures and customs and also animal fauna. The infection rate is higher in warm and humid climates and lower in arid and cold areas (Assmar et al 1997;Lainson et al 2005;Lehmann et al 2006).…”

The molecular epidemiology of parasite infections: Tools and applications

“…In Europe and North America, Toxoplasma gondii is considered to have a predominantly clonal population structure, with three main clonal lineages, referred to as Types I, II and III, accounting for >85% of strains isolated from humans and domestic animals [59]. However, recent studies of isolates of T. gondii in wildlife from North and South America, as well as Australia have uncovered more biological and genetic diversity [60,61,62]. Although some strains infecting wildlife appear to be recombinant genotypes derived from crosses between the archetypal clonal lineages, others are atypical strains which possess completely novel alleles.…”