Isolation and genotyping of Toxoplasma gondii causing fatal systemic toxoplasmosis in an immunocompetent 10-year-old cat

A 10-year-old male, neutered domestic shorthair cat was presented with fever, anorexia, vomiting, and diarrhea. Serologic testing for Feline immunodeficiency virus and Feline leukemia virus were negative. Fine-needle aspirates of mesenteric lymph nodes revealed the presence of banana-shaped apicomplexan parasites. The cat died after 4 days of hospitalization. Postmortem polymerase chain reaction (PCR) analysis confirmed the presence of Toxoplasma gondii in all examined organs. Parasites were ex vivo isolated in outbred mice and subsequently transferred into cell culture. Genotyping, using genetic markers for SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico for PCR-restriction fragment length polymorphism, revealed infection with type II T. gondii displaying type II alleles at all loci except Apico, which exhibited a type I allele. This is the most frequently identified genotype among cats acting as definitive hosts in central Europe, but to the authors' knowledge, it has never been associated with systemic toxoplasmosis in an adult, immunocompetent cat.