MOLECULAR GENETICS, GENOMICS, AND PHYLOGENETICS OF FOODBORNE ZOONOTIC PARASITES AFFECTING FOOD SAFETY AND PUBLIC HEALTH
Location: Animal Parasitic Diseases
Title: A monomorphic halotype of chromosome Ia is associated with widespread success in clonal and nonclonal populations of Toxoplasma gondii
Submitted to: mBio
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 11, 2011
Publication Date: December 1, 2011
Citation: Khan, A., Miller, N., Roos, D., Dubey, J.P., Ajzenburg, D., Darde, M., Ajioka, J.W., Rosenthal, B.M., Sibley, L. 2011. A monomorphic halotype of chromosome Ia is associated with widespread success in clonal and nonclonal populations of Toxoplasma gondii. mBio. 2:e00228-11.
Interpretive Summary: We do not have a good understanding of the biological basis for the widespread dispersal of certain strains of Toxoplasma gondii, the zoonotic agent of human toxoplasmosis (which endangers human reproductive health and is a major opportunistic pathogen in AIDS patients). Our objectives here were to learn how many different lineages of this parasite have inherited a particular version of one chromosome that appears to have become especially widespread.In particular, we genotyped isolates in North and South America and found that many of these, though otherwise quite distinct, share this particular heritable feature. This study will contribute to our understanding of the epidemiology of the parasite and may help hone efforts to understand the genetic basis for its success, which will benefit epidemiologists, livestock producers, and public health more broadly.
Toxoplasma gondii is a widespread parasite of animals that causes zoonotic infection in humans. Previous studies have revealed a strongly clonal population structure in North America and Europe, while strains from South American are genetically divergent and show greater evidence of recombination. The common inheritance of a monomorphic version of chromosomeIa (ChrIa) among clonal strains from North America and Europe led to the previous suggestion that this chromosome was associated with their recent clonal expansion. To further examine the diversity and distribution of ChrIa, we profiled a large number of strains from different continents. Our findings reveal that the same version of ChrIa is found in both clonally propagating strains in North America and somewhat older strains in South America, where the parasite propagates primarily sexually. Although northern and southern strains harbor the same conserved ChrIa, strains from these two continents are genetically separate and show limited evidence of recent mixing. Whole genome detection of shared polymorphisms detected by microarray hybridization provides evidence for an ancestral flow from several ancient southern lineages that gave rise to the clonal lineages in North America. Collectively, these data indicate that a common version of ChrIa is wide spread among strains in South America, and has more recently been associated with expansion of specific lineages by clonal expansion in North America and Europe. The findings have significance for mechanisms of spread of virulence determinants at the population level.