Zoonotic and ecological implications of parasites in a popular edible fish, Saurida tumbil (Family Synodontidae): Insights from review and original research

Saurida tumbil, is a commercially valuable fish which is found in 36 countries and islands across Africa, Asia, and Oceania. It serves as a key food resource for many coastal communities, making the identification and assessment of its parasitic biota important for food safety and ecological monitoring. In this study, 140 specimens of S. tumbil, obtained from local fish markets were examined for foodborne parasites using both morphological and molecular approaches. A total of 123 nematodes, all alive, were collected from 33 infected fish. We also conducted an extensive review of parasites previously associated with this fish species. Our findings based on the examination of fish and the literature review reveal that S. tumbil hosts a diverse range of parasites, such as protozoans, nematodes, and tapeworms, several of which present potential zoonotic risks. Key discoveries include the first identification of Anisakis larval type III as A. brevispiculata, as well as evidence that Anisakis larval type I consists of two genetically distinct species, both labelled as A. typica in GenBank despite exhibiting greater genetic divergence. Anisakis nematodes are a known seafood borne parasites. Additionally in the literature, another parasite, trypanorhynch tapeworm larvae, were commonly found in this fish. Although human infections with trypanorhynch larvae are rare, similar to anisakids they can cause allergic reactions and reduce the marketability of fish due to consumer aversion caused by presence of parasites in fish flesh. Our results also highlight the challenges posed by mislabelled sequences in GenBank, which complicate the accurate identification of parasite larvae. These inaccuracies impede species-level identification, obscure the true diversity and zoonotic potential of these parasites, and ultimately hinder effective monitoring and public health responses. Our results contribute to a better understanding of Saurida tumbil's role as a host for diverse parasite species with both ecological and zoonotic significance.