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A minimum of 11 genera of parasites, including 7 known or suspected to cause zoonoses, were detected in dogs in 2 northern Canadian communities. Dogs in remote settlements receive minimal [...]

Toxoplasma gondii is a highly prevalent protozoan parasite that infects a wide range of animals and threatens human health by contaminating food and water. A markedly limited number of clonal parasite lineages have been recognized as predominating in North American and European populations, whereas strains from South America are comparatively diverse. Here, we show that strains from North America and Europe share distinct genetic polymorphisms that are mutually exclusive from polymorphisms in strains from the south. A striking exception to this geographic segregation is a monomorphic version of one chromosome (Chr1a) that characterizes virtually all northern and many southern isolates. Using a combination of molecular phylogenetic and phenotypic analyses, we conclude that northern and southern parasite populations diverged from a common ancestor in isolation over a period of [approximately equal to] [10.sup.6] yr, and that the monomorphic Chr1a has swept each population within the past 10,000 years. Like its definitive feline hosts, T. gondii may have entered South America and diversified there after reestablishment of the Panamanian land bridge. Since then, recombination has been an infrequent but important force in generating new T. gondii genotypes. Genes unique to a monomorphic version of a single parasite chromosome may have facilitated a recent population sweep of a limited number of highly successful T. gondii lineages. biogeography | evolution | pathogen | transmission | virulence

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

Water was the suspected vehicle of Toxoplasma gondii dissemination in a toxoplasmosis outbreak in Brazil. A case-control study and geographic mapping of cases were performed. T. gondii was isolated directly [...]

Strains of Toxoplasma gondii can be grouped into three predominant clonal lineages with members of the type I group being uniformly lethal in mice. To elucidate the basis of this extreme virulence, a genetic cross was performed between a highly virulent type I strain (GT-1) and a less-virulent type III strain (CTG), and the phenotypes of resulting progeny were analyzed by genetic linkage mapping. Analysis of independent recombinant progeny identified several quantitative trait loci that contributed to acute virulence. A major quantitative trait locus located on chromosome VII accounted for [approximately equal to] 50% of the virulence phenotype, whereas a minor locus on chromosome IV, linked to the ROP1 gene, accounted for [approximately equal to] 10%. These loci are conserved in other type I strains, indicating that acute virulence is controlled by discrete genes common to the type I lineage. QTL mapping | genetics | parasite | linkage analysis

A laboratory method for detecting Toxoplasma gondii oocysts in drinking water at the Humpback Reservoir in British Columbia was described. The case-control study was conducted in response to a community outbreak of toxoplasmosis in the area. An aeration technique was used to sporulate and render infectious any Toxoplasma gondii oocysts in the sediment. Results showed that the Humpback Reservoir was the source of the Toxoplasma gondii oocysts. It was concluded that contamination of the drinking water occurred during periods of high runoff at the reservoir.

The effect of ultraviolet (UV) exposure on the viability of Toxoplasma gondii oocysts is examined and has determined the UV fluence required for a 3-[log.sub.10] inactivation by using three analytical approaches. The three approaches have included a SCID mouse bioassay, a quantitative reverse transcriptase real-time PCR (RT-qPCR) assay and an in-vitro Tocoplasma gondii oocyst plaque (TOP) assay.