Subtype analysis of Blastocystis spp. isolated from domestic mammals and poultry and its relation to transmission to their in-contact humans in Ismailia governorate, Egypt

Background: Blastocystis is a common protist detected in fecal samples of humans and a wide range of animals. The parasite exhibits extensive genetic diversity with seventeen distinct subtypes (STs) identified collectively from humans, other mammals and birds. Shared STs between animal and human hosts were considered to be potentially zoonotic. However. Blastocystis infection among non-human hosts, in Egypt has not been investigated so far. Objective: To determine the occurrence and ST distribution of Blastocystis species isolated from domestic mammals, poultry and their in-contact humans. Material and Methods: A total of 416 fecal samples from domestic animals (mammals and poultry) as well as their in-contact humans were screened by inoculation into Jones' media. Positive samples were subtyped using seven pairs of ST-specific sequence-tagged-site (STS) primers. Results: The occurrence of Blastocystis spp. infection was 69.8% in poultry, 17.7.4 in domestic mammals and 35.7% in humans. Among the studied animal species ST1-ST7 were identified with varying percentages; however, only four STs (ST1-ST4) were identified in humans. A minority of human subjects examined (16/56, 28.5%) were carrying the same ST detected in their domestic animals. Conclusion: The detection of all the tested STs among the infected animal species examined highlights the broad genetic diversity observed among Blastocystis spp. isolated from animals. However, the detection of only four STs among humans suggests that these STs can easily infect humans and the animals carrying the same STs could be possible reservoirs. Surprisingly, direct handling of animals was not found to be a major contributor to human blastocystosis in Egypt, denoting the role of anthroponotic transmission and the possibility of fecal cross-contamination from other potential reservoir animals in the surrounding environment.