Characterization of Blastocystis species infection in humans and mantled howler monkeys, Alouatta palliata aequatorialis, living in close proximity to one another.

This study characterizes Blastocystis species infections in humans and mantled howler monkeys, Alouatta palliata aequatorialis, living in close proximity to one another in northwestern Ecuador. Blastocystis species were identified from 58 of 96 (60.4 %) mantled howler monkey fecal samples, and 44 of 55 human fecal samples (81.5 %) by polymerase chain reaction. Using single-stranded conformation polymorphism, we were able to efficiently separate and sequence subtypes (STs) within mixed samples without the need for cloning. Blastocystis ST1, ST2, and ST3 were found in people, and two individuals were infected with more than one subtype. All monkey samples were ST8. The lack of shared subtypes between humans and monkeys suggests that no Blastocystis transmission occurs between these species in spite of close proximity in some instances. Based on analysis of demographic data from a questionnaire given to human participants, individuals who boiled their water before consumption were significantly less likely to be infected with Blastocystis (44.4 %) compared to those who did not (93.8 %) (p = 0.002). No other risk factors were significant, although hunters, females, individuals living in large families, and those living closer to forested habitat tended to have a higher proportion of Blastocystis infections.