A survey of Blastocystis sp. in livestock, pets, and zoo animals in Japan

The prevalence of Blastocystis sp. was examined in fecal samples collected from cattle, pigs, dogs, and a variety of zoo animals (primates, carnivores, herbivores, pheasants, and ducks) by direct observation of fresh fecal suspensions or cultured materials, using light microscopy. The cattle and pigs were randomly sampled from 11 and 12 commercial farms, respectively, located in the western region of Japan. The dog material used in this study was obtained from pets housed in an animal shelter in the city of Osaka. Zoo animals were chosen based on housing conditions that minimized the possibility of intra-zoo transmission of the organism. The prevalence rate among the groups varied greatly. A high prevalence of infection was observed in the farm animal group, ranging from 95% (58/61) in pigs to 71% (39/55) in cattle, whereas the dog fecal samples were completely free of the organism. Prevalence of the organism in the zoo animal were 85% (29/34) in primates, 80% (8/10) in pheasants, 56% (9/16) in ducks, and 0% (0/58) in various carnivores and herbivores. Among the zoo animals infected with Blastocystis, eight species of primates, eight species of pheasants, and four species of ducks were confirmed as new hosts. Since Blastocystis organisms isolated from various animals were morphologically indistinguishable from Blastocystis hominis by light microscopy, further genomic studies are required for analysis of the zoonotic potential or etiological significance of these isolates.