TOXOPLASMA-GONDII COMPRISES 3 CLONAL LINEAGES - CORRELATION OF PARASITE GENOTYPE WITH HUMAN-DISEASE

The population genetic structure of Toxoplasma gondii was determined b y multilocus restriction fragment length polymorphism analysis at 6 lo ci in 106 independent isolates from humans and animals, Phylogenetic a nd statistical analyses indicated a highly unusual population structur e consisting of 3 widespread clonal lineages. Extensively mixed genoty pes were only apparent in 4 strains, which indicated that, while not s eparate species, sexual recombination between the 3 lineages is exceed ingly rare in natural populations, T. gondii is a major cause of subcl inical human infection and an important opportunistic pathogen that ca uses severe disease in immunocompromised patients. While strains from all 3 lineages were isolated from humans, the majority of human toxopl asmosis cases were associated with strains of a type II genotype. The correlation of specific clonal lineages with human toxoplasmosis has i mportant implications for development of vaccines, drug treatments, an d diagnostic protocols.