Research Article Epidemiologic Study of Blastocystis Infection in an Urban Community in the Philippines Maria Luz B. Belleza, 1 Jessa Louise C. Cadacio, 2 Maridel P. Borja, 3 Juan Antonio A. Solon, 1 Mildred A. Padilla, 4 Pilarita N. Tongol-Rivera, 1 and Windell L. Rivera 5,6 1 Department of Parasitology, College of Public Health, University of the Philippines, Ermita, 1000 Manila, Philippines 2 College of Medicine, University of the Philippines, Ermita, 1000 Manila, Philippines 3 Department of Epidemiology and Biostatistics, College of Public Health, University of the Philippines, 1000 Manila, Philippines 4 Department of Veterinary Paraclinical Sciences, College of Veterinary Medicine, University of the Philippines, Los Ba˜ nos, 4031 Laguna, Philippines 5 Institute of Biology, College of Science, University of the Philippines, Diliman, 1101 Quezon City, Philippines 6 Molecular Protozoology Laboratory, Natural Sciences Research Institute, University of the Philippines, Diliman, 1101 Quezon City, Philippines Correspondence should be addressed to Windell L. Rivera; wlrivera@science.upd.edu.ph Received 1 March 2015; Accepted 29 April 2015 Academic Editor: Pam R. Factor-Litvak Copyright © 2015 Maria Luz B. Belleza et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Blastocystis has been considered as the most common intestinal parasite in humans and has an augmented impact on public health. However, the prevalence of this parasite in the Philippines has not been determined. To contribute to a better understanding of the epidemiology of this infection, a cross-sectional study aimed at providing the frst documented data on the prevalence and correlates, sociodemographic factors, hygiene practices, source of water supply, and dog ownership, associated with Blastocystis infection was carried out in randomly selected communities at Pateros, Metro Manila. Fecal samples from respondents were collected and cultured in diphasic agar medium for 3–7 days and examined using light microscopy. Of the 1,271 respondents, 12.98% (95% CI: 11.13–14.83) were detected positive for Blastocystis. Among the correlates of Blastocystis infection, dog ownership was found signifcantly associated as confrmed by multivariate analysis. Terefore, this factor should be considered in information to create awareness about Blastocystis and to prevent and control Blastocystis infection in particular and diarrheal diseases in general. Further studies using molecular approaches to distinguish subtype and to determine genetic characteristics of isolates from humans and dogs are recommended to analyze their relationship and provide more conclusive evidence of cross-transmission. 1. Introduction Blastocystis sp. is currently the most common intestinal protist found in human feces and is considered an emerging parasite with a worldwide distribution [1, 2]. Te accepted mode of transmission of the parasite is through the fecal- oral route [3]. Its pathogenic role in humans remains uncertain since Blastocystis infections are both symptomatic and asymptomatic [1]. Nevertheless, it is being associated with various nonspecifc gastrointestinal symptoms including diarrhea, abdominal pain, fatulence, anorexia, nausea, and vomiting [4]. Te parasite may also be linked to irritable bowel syndrome and infammatory bowel disease [5–8]. Te prevalence of Blastocystis infection is generally higher in developing than in industrialized countries partly because of poor sanitary conditions, consumption of contaminated food or water, and close animal contact [9–12]. Blastocystis infection is being linked with demographic factors such as age, gender, and level of education as well as exposure factors such as hygiene, source of water supply, and exposure to animals [13–16]. Moreover, higher risks of infection and high prevalence have been identifed in food and animal handlers, Hindawi Publishing Corporation Journal of Environmental and Public Health Volume 2015, Article ID 894297, 7 pages http://dx.doi.org/10.1155/2015/894297