High prevalence of Blastocystis sp. in pigs reared under intensive growing systems: frequency of ribotypes and associated risk factors.

Three hundred and ninety-five pig fecal samples were analyzed looking for Blastocystis sp. using optical microscopy and PCR. A global prevalence of 46.8% has been observed in this study, although relative values of prevalence differ notably according to the strata examined, ranging from 9.3% in sows to 75% in weaners. Statistic analysis of the data included several risk factors such as different management systems, date of sample collection, fecal consistency, age and sex of the animals. The presence of the parasite was statistically associated to the variables "age" and "date of sample collection", being more prevalent in weaners and grower pigs and warm season. Random fragment-length polymorphism (RFLP-PCR) analysis of positive PCR samples revealed a high homology in the digestion pattern, appearing as two ribotypes. The results were further confirmed by sequencing of ten randomly selected samples, showing that the samples obtained in this study were included in two genotypes: genotype I previously named by Noël et al. [Noël, C., Dufernez, F., Gerbod, D., Edgcomb, V.P., Delgado-Viscogliosi, P., Ho, L.-Ch., Singh, M., Wintjens, R., Sogin, M.L., Capron, M., Pierce, R., Zenner, L., Viscogliosi, E., 2005. Molecular phylogenies of Blastocystis isolates from different hosts: implications for genetic diversity, identification of species, and zoonosis. J. Clin. Microbiol. 43, 348-355], in which Blastocystis sp. sequences from humans, pigs and cattle were included, and genotype II, which only included Blastocystis hominis sequences obtained from human and other primates. This is the first report including Blastocystis sequences from swine origin in genotype II.