Zoonotic and genetically diverse subtypes of Blastocystis in U.S. dairy calves

Authors: MALONEY, JENNY - Orise Fellow; LOMBARD, JASON - Animal And Plant Health Inspection Service (APHIS); URIE, NATALIE - Animal And Plant Health Inspection Service (APHIS); SHIVLEY, CHELSEY - Animal And Plant Health Inspection Service (APHIS); Santin-Duran, Monica

Submitted to: Parasitology Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2018
Publication Date: 11/27/2018
Citation: Maloney, J., Lombard, J., Urie, N., Shivley, C., Santin, M. 2018. Zoonotic and genetically diverse subtypes of Blastocystis in U.S. dairy calves. Parasitology Research. 118(2):575-582. https://doi.org/10.1007/s00436-018-6149-3.
DOI: https://doi.org/10.1007/s00436-018-6149-3

Interpretive Summary: Blastocystis is an enteric parasite commonly found in humans and many animals worldwide. Although its role as an agent of disease has been controversial, Blastocystis spp. has been reported in recent studies as a human pathogen associated with both intestinal and extra-intestinal disorders. Its high prevalence in humans has been associated with poor hygiene, exposure to animals, and consumption of contaminated food or water. Despite its high prevalence and ubiquitous presence, limited data exist on the occurrence and genetic diversity of Blastocystis in the United States and in food animals. We conducted the first large-scale molecular investigation of Blastocystis in the United States by testing 2,539 fecal samples from dairy heifer calves from 13 states. Blastocystis was detected in 73 (2.9%) fecal samples, and molecular characterization showed a wide diversity of subtypes. Eleven subtypes were identified, seven previously reported (ST-3, ST-4, ST-5, ST-10, ST-14, ST-17, and ST-21) and four novel subtypes (named ST-23 to ST-26). Zoonotic subtypes 3, 4, and 5 were found in 67% (49) of the positive specimens in this population. This study highlights the potential risk of zoonotic transmission and suggests that the role of cattle in transmission of human infections requires further study. This research provides beneficial information to physicians, veterinarians and epidemiologists concerned with this widespread parasite.

Technical Abstract: Blastocystis is an emerging zoonotic pathogen with global distribution. However, limited data exist on the occurrence and genetic diversity of Blastocystis in the United States and in food animals. We conducted the first large-scale molecular investigation of Blastocystis in the United States by testing 2,539 fecal samples from dairy heifer calves from 13 states. Blastocystis was detected in 73 (2.9%) fecal samples, and molecular characterization showed a wide diversity of subtypes. Eleven subtypes were identified, seven previously reported (ST-3, ST-4, ST-5, ST-10, ST-14, ST-17, and ST-21) and four novel subtypes (named ST-23 to ST-26). Zoonotic subtypes 3, 4, and 5 were found in 67% (49) of the positive specimens in this population. Our results suggest that cattle could serve as important reservoirs of infection for humans and other domestic animals highlighting the potential risk of zoonotic transmission for Blastocystis.