Subtype analysis of Blastocystis sp. isolates from human and canine hosts in an urban community in the Philippines.

Blastocystis sp. is a common gut-dwelling protist of both humans and animals. A cross-sectional survey among humans and their dogs was conducted to determine the prevalence of Blastocystis infection and to characterize the subtype (ST) distribution in an urban community in the Philippines. Fecal specimens from 1,271 humans and 145 dogs were collected and inoculated in diphasic culture medium. Prevalence of Blastocystis by culture was 13.0% (95% CI = 11.2-15.0) and 14.5% (95% CI = 9.6-21.2) for humans and dogs, respectively. A total of 168 culture isolates were genotyped using polymerase chain reaction (PCR) with seven pairs of ST-specific sequence-tagged-site (STS) primers. In humans, the ST present in this study were ST1 with 22.6% (95% CI = 17.2-29.0), ST2 with 3.1% (95% CI = 1.3-6.7), ST3 with 41.4% (95% CI= 34.9-48.6), ST4 with 14.8% (95% CI = 10.5-20.6), ST5 with 4.1% (95% CI = 2.0-8.0), and unknown ST with 13.9% (95% CI = 9.6-19.4). In dogs, the ST present in this study were ST1 with 4.3% (95% CI = 0.0-29.0), ST2 with 8.7% (95% CI = 1.3-28.0), ST3 with 17.4% (95% CI = 6.4-37.7), ST4 with 13.0% (95% CI = 3.7-33.0), ST5 with 13.0% (95% CI = 3.7-33.0), and unknown ST with 47.8% (95% CI = 29.2-67.0). This is the first study that reported Blastocystis ST4 in human and canine hosts in the Philippines.

Subtype analysis of Blastocystis sp. isolates from asymptomatic individuals in an urban community in the Philippines

Blastocystis sp. is a commonly reported enteric protistan parasite in faecal specimens with a worldwide distribution afflicting both humans and a wide range of animals. The aim of this study is to characterize the subtypes (STs) of Blastocystis sp. isolates from asymptomatic individuals in an urban community in Pateros, Metro Manila, Philippines. The 600-bp small subunit ribosomal RNA (SSU rRNA) barcoding region of Blastocystis sp. isolates was amplified and sequenced using the primers RD5 and BhRDr. Subtypes were identified by uploading the sequences onto the Basic Local Alignment and Search Tool (BLAST) websites, the Blastocystis Subtype (18S) and Sequence Typing (MLST) Database and by construction of a phylogenetic tree. Twenty-nine (29) out of 35 individuals were detected positive for Blastocystis sp. ST3 is the most common among the three STs detected (65.5%), followed by ST1 (31.0%) and ST4 (3.44%). This study showed that DNA barcoding can serve as a helpful tool to investigate the diversity of Blastocystis sp. in the Philippines.

Epidemiologic Study of Blastocystis Infection in an Urban Community in the Philippines.

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 first 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 significantly associated as confirmed by multivariate analysis. Therefore, 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.