Feline toxoplasmosis in Finland: cross-sectional epidemiological study and case series study.

Three subgroups of the Finnish cat population underwent investigation for different aspects of feline toxoplasmosis. Blood samples of 445 purebred pet cats and 45 shelter cats were screened for Toxoplasma gondii-specific immunoglobulin G antibodies with a direct agglutination test. The overall seroprevalence was 48.4%; older cats and cats receiving raw meat in their diet were more often seropositive. Fecal samples were obtained from 131 shelters cats; 2 of the cats were found shedding T. gondii-like oocysts, and the oocysts shed by 1 of the 2 were confirmed as T. gondii with polymerase chain reaction. Among 193 cats submitted for necropsy during a 3.5-year period, 6 (3.1%) had been diagnosed with generalized toxoplasmosis and were retrospectively further investigated. The main pathological lesions included acute interstitial pneumonia, acute necrotizing hepatitis, and nonsuppurative meningoencephalitis with glial granulomas. Immunohistochemical staining demonstrated a mild to massive parasite burden in tissues with pathological lesions as well as in unaffected tissues. The results of the direct multilocus genotyping of T. gondii parasites detected were consistent with endemic genotype II, and the causative parasite strains were isolated from 2 of the generalized toxoplasmosis cases. The results indicate that cats in Finland commonly encounter T. gondii and contribute to the environmental oocyst burden, while the endemic genotype II can also prove fatal to the parasite's definitive host. Preventing feline T. gondii infections is not only of public health importance but also a welfare issue for the cats themselves.