Toxoplasma gondii genotyping in 2,467 human toxoplasmosis cases from France and other geographical origins: genetic diversity and clinical associations

Type II Toxoplasma gondii predominated in 2,467 French and overseas human cases (82.6% overall; 91.0% of congenital), yet it also caused severe congenital and acquired ocular disease.

• Why it matters: Parasite genetic diversity is well documented, but how specific T. gondii genotypes relate to human clinical forms has remained unclear.
• What they did: The study retrospectively genotyped 2,467 T. gondii-positive clinical cases using 15 standardized microsatellite markers, yielding complete genotypes for 1,269 cases and 13 genetic groups.
• The result: Haplogroup 16 was linked to severe congenital toxoplasmosis (6/7 severe), Amazonian strains were almost exclusively severe acquired ocular disease in immunocompetent patients, and Africa 1 strains were associated with isolated cerebral toxoplasmosis in immunodeficient patients (20/25).