Zoonotic nematode parasites infecting selected edible fish in New South Wales, Australia

Despite increases in the annual consumption of seafood in Australia, studies on the occurrence and prevalence of zoonotic parasites in fish and the risk they may pose to human health are limited. The present study was aimed at determining the occurrence of zoonotic nematodes in commonly consumed fish in New South Wales, Australia's most populous state. Three species of fish, including the Australian pilchard, Australian anchovy, and eastern school whiting, were purchased from a fish market and examined for the presence of nematode parasites. All Australian pilchards examined in this study were infected (100%; n = 19), followed by the eastern school whiting (70%; n = 20) and Australian anchovy (56%; n = 70). Nematodes were in the larval stage and, therefore, classified by morphotype, followed by specific identification through sequencing of their internal transcribed spacer (ITS) regions. Seven different larval types with zoonotic potential, belonging to the families Anisakidae (Contracaecum type II and Terranova type II) and Raphidascarididae (Hysterothylacium types IV [genotypes A and B], VIII, XIV and a novel Hysterothylacium larval type, herein assigned as type XVIII), were found. The new larval type was identified as Hysterothylacium thalassini, based on ITS sequence data. The presence of the infective stage of a range of zoonotic parasites in fish commonly consumed in New South Wales is important, particularly as, in some dishes, these fish are used whole, raw or undercooked. This study provides the basis for future research on other aspects of these parasites, in regards to public health.