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United States Department of Agriculture

Agricultural Research Service

Research Project: MOLECULAR SYSTEMATICS AND COMPARATIVE POPULATION GENETICS OF PARASITIC ORGANISMS THAT THREATEN FOOD SAFETY AND SECURITY Title: Genetic diversity of Toxoplasma gondii in animals and humans

Authors
item Sibly, L.DAVID - WASH. UNIV. SCH. OF MED
item Khan, Asis - WASH. UNIV. SCH. OF MED
item Ajioka, Jim - UNIV OF CAMBRIDGE, UK
item Rosenthal, Benjamin

Submitted to: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
Publication Type: Review Article
Publication Acceptance Date: August 1, 2009
Publication Date: August 18, 2009
Citation: Sibly, L., Khan, A., Ajioka, J., Rosenthal, B.M. 2009. Genetic diversity of Toxoplasma gondii in animals and humans. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 364:2749-2761.

Interpretive Summary: The natural occurrence and clincial importance of genetic variation in Toxoplasma gondii is discussed in this comprehensive review of recent progress in genotyping procedures and their application to natural parasite samples.

Technical Abstract: Toxoplasma gondii is one of the most common parasites of domestic, wild, and companion animals, and it also infects approximately 25% of the world’s human population. T. gondii has a complex life cycle. Sexual development occurs only in the cat gut, while asexual replication and transmission occur in many vertebrate hosts. These features combine to create an unusual population structure. The vast majority of strains in North America and Europe fall into three recently derived, clonal lineages known as types I, II, and III. Recent studies have revealed that South American strains are more genetically diverse and comprise distinct genotypes from those seen in the North. These differences have been shaped by infrequent sexual recombination, population sweeps, and biogeography. The majority of human infections that have been studied in North America and Europe are caused by type II strains, which are also common in agricultural animals from these regions. In contrast, several diverse genotypes of T. gondii are associated with severe infections in humans in South America. Defining the population structure of T. gondii from new regions has important implications for transmission, immunogenicity, and pathogenesis.

Last Modified: 8/22/2014