title: Toxoplasma gondii comprises three clonal lineages: correlation of parasite genotype with human disease.
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.
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: D K
authors.initials: DK
authors.lastname: Howe
authors.forename: L D
authors.initials: LD
authors.lastname: Sibley
mesh_terms: D000818:Animals; D001483:Base Sequence; D005838:Genotype; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D014122:Toxoplasma / Q000235:genetics*; D014123:Toxoplasmosis / Q000209:etiology*