Outbreak of toxoplasmosis in four squirrel monkeys (Saimiri sciureus) in Japan

Toxoplasma gondii is a protozoan parasite that causes fatal disease in New World monkeys. Several reports have described outbreaks of toxoplasmosis in squirrel monkeys. Here, we report the death of four squirrel monkeys in a captive colony from acute toxoplasmosis, one of which developed toxoplasmosis about 1 year after the initial outbreak. Serum anti–T. gondii antibody was detected by a latex agglutination test in the animals, and one presented seropositive before clinical signs were observed. Macroscopically, the lungs were severely affected and three animals showed pulmonary edema. Microscopically, interstitial pneumonia was observed in all animals. In the liver and heart, multifocal mononuclear cell infiltration with necrosis was detected. Parasite loading tended to be higher in the lungs, liver and heart than in the spleen, kidney and brain. The parasite was isolated from the brain of one animal and this isolate showed type II restriction patterns in the SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2 and PK1 genes of T. gondii and type I restriction patterns in the L358 and Apico genes by PCR-Restriction Fragment Length Polymorphism analysis. The clinical signs were reduced in mice infected with this isolate compared with those infected with reference type II strain PLK in a bioassay. To our knowledge, this is the first report of isolation of the parasite from squirrel monkeys in Japan and offers the opportunity for genomic and pathogenic analyses to aid our understanding of acute toxoplasmosis.