Subtype distribution and genetic characterizations of Blastocystis in pigs, cattle, sheep and goats in northeastern China's Heilongjiang Province.

Blastocystis is a common protozoan found in the surveys of human and animal fecal specimens. Extensive genetic diversity has been observed within the genus Blastocystis. At least 17 subtypes (ST) have been identified in mammals and birds, nine of which (ST1 to ST9) have been identified in humans. In China, although there have been a few reports on Blastocystis infection in humans and many animal species, no epidemiological data are available in either humans or animals in northeastern China's Heilongjiang Province. To determine infection rates and subtype distributions of Blastocystis in pigs, cattle, sheep and goats, to understand genetic characterizations and to assess zoonotic possibility of Blastocystis isolates, 337 fecal specimens from livestock (68 from pigs, 147 from cattle, 109 from sheep and 13 from goats) were collected in northeastern China's Heilongjiang Province. Each of them was detected for Blastocystis by PCR amplification of the partial SSU rRNA gene. An average infection rate of Blastocystis was 7.7% (26/337), and the highest infection rate was found in 9.5% (14/147) in cattle, followed by 8.8% (6/68) in pigs and 5.5% (6/109) in sheep. There was an absence of Blastocystis in goats. Five Blastocystis subtypes were identified: ST5 (n=6) in pigs; ST3 (n=2), ST10 (n=10) and ST14 (n=2) in cattle; ST1 (n=1), ST5 (n=1), ST10 (n=3) and ST14 (n=1) in sheep. 38.5% (10/26) of Blastocystis isolates belong to potentially zoonotic subtypes based on the previous findings of ST1, ST3 and ST5 in humans. This is the first report of Blastocystis in pigs, cattle and sheep in northeastern China's Heilongjiang Province. ST1, ST5 and ST14 were identified in sheep for the first time. Due to the low infection rate of Blastocystis and the small percentage of potentially zoonotic subtypes in these livestock, there is a minimal risk of zoonotic transmission of Blastocystis.