Toxoplasma gondii Comprises Three Clonal Lineages: Correlation of Parasite Genotype with Human Disease

TLDR

Toxoplasma gondii commonly causes subclinical infection and severe disease in immunocompromised individuals. The study seeks to link specific clonal lineages of T. gondii to human toxoplasmosis to guide vaccine, drug, and diagnostic development. Researchers characterized the parasite’s population genetics by multilocus RFLP at six loci across 106 isolates from humans and animals.

Abstract

The population genetic structure of Toxoplasma gondii was determined by multilocus restriction fragment length polymorphism analysis at 6 loci in 106 independent isolates from humans and animals. Phylogenetic and statistical analyses indicated a highly unusual population structure consisting of 3 widespread clonal lineages. Extensively mixed genotypes were only apparent in 4 strains, which indicated that, while not separate species, sexual recombination between the 3 lineages is exceedingly rare in natural populations. T. gondii is a major cause of subclinical human infection and an important opportunistic pathogen that causes severe disease in immunocompromised patients. While strains from all 3 lineages were isolated from humans, the majority of human toxoplasmosis cases were associated with strains of a type II genotype. The correlation of specific clonal lineages with human toxoplasmosis has important implications for development of vaccines, drug treatments, and diagnostic protocols.