Infectivity of Blastocystis isolates from chickens, quails and geese in chickens

The infectivity of six Blastocystis isolates obtained from two domestic chickens, two Japanese quails and two domestic geese, were examined in 1-week-old male chicks. All six isolates were able to infect the chicks via the intracecal inoculation of 1×10⁶ cells of cultured organisms. Since the infected chicks discharged many cysts in their feces, the infectivity of the concentrated cysts in chicks was compared among three isolates from different bird species. The CK86-1 and QQ93-3 isolates, which were obtained from a chicken and a quail, respectively, were successfully infected in chicks by orally inoculating with 1×10²–1×10⁶ cysts. On the other hand, the AC03-1 isolate from a goose required more cysts to infect the chicks, from 1×10³ cysts to 1×10⁶ cysts. In addition, when an uninfected normal chick was housed with five experimentally inoculated chicks with cysts of the QQ93-3 isolate, the normal chick became infected, indicating the fecal–oral transmission of the cyst form among the birds. These results show that the transmission of Blastocystis infection occurs easily between the same or different bird species. Therefore, the proposal of new Blastocystis species on the basis of different avian host species is problematic.