Prevalence and molecular identification of fish-borne trematodes in endemic communities in Caraga region, Mindanao, Philippines.

The fish-borne trematodes are a group of parasitic flatworms whose life cycle successively passes through various snails and fresh and brackish water fish, and terrestrial vertebrate hosts including humans. Human infection is common in countries where eating raw fish is practiced such as in the Philippines. Limited investigation in endemic areas along with misdiagnosis makes it challenging to address these infections. Therefore, this study aimed to investigate the prevalence, identify risk factors for, and molecularly identify fish-borne trematodes in eight helminth-endemic communities in Mindanao, Philippines through a household-based cross-sectional study. Fecal samples were collected from 1152 residents (age 10-59 years) from 386 households in the study communities and from 92 dogs and cats. These were examined microscopically for trematode infections. Molecular analysis of microscopy-positive fecal samples was conducted using the internal transcribed spacer 2 region (ITS2) gene. Further, household-heads were surveyed to investigate risk factors for infection. The overall prevalence of infection in humans was 4.1 % (n = 47), with higher infection prevalence in Surigao del Norte province, where fish is often eaten raw or undercooked (as kinilaw and sugba). Males and adults were found to be more at risk of infection. Only 2 animals were positive, both of which are dogs. Molecular findings revealed three fish-borne trematode species: Haplorchis taichui, Stellanthchasmus falcatus, and Opisthorchis viverrini. To our knowledge, this study reports the first molecular identification of fish-borne trematodes in the Philippines. The results help address knowledge gaps on fish-borne trematodes in the Philippines and can be employed to improve control using evidence-based and targeted approaches.