Morphological and Phylogenetic Analysis of Eustrongylides sp. and Gnathostoma spinigerum Parasitizing the Asian Swamp Eel Monopterusalbus in China

Infection levels of Gnathostomatidae (Nematoda) larvae in commercial fishes in north-eastern Australian waters and related food safety concerns

The majority of research on the safety of marine edible fish has primarily focused on anisakid nematodes, neglecting the potential risks posed by other parasites, including those belonging to the family Gnathostomatidae. In Australia, there have been few reported cases of human infections with gnathostomatid parasites since 2011. However, due to the absence of a standardized diagnostic test in the country, it is believed that the actual number of infections is higher than reported. This study aimed to assess the occurrence and prevalence of infectious gnathostomatid parasites in selected commercial fish species in Australia. A total of 1947 marine fish from northern Australia, representing 9 families, 16 genera, and 30 species, were examined for gnathostomatid nematode infections. Overall, 12.3 % of the fish were found to be infected with at least one gnathostomatid larva. Among the species examined, the yellow-dabbled flounder (Branchypleura novaezeelandiae) exhibited the highest prevalence (83.3 %; n = 6) and the largest number of gnathostomatid larvae. The identification of the gnathostomatid larvae was confirmed as belonging to the genus Echinocephalus based on both morphological characteristics and sequence data. No significant correlation was observed between the prevalence, mean abundance, and mean intensity of infection with the length or weight of the examined fish species. Notably, several of the infected fish species are considered popular choices in the Australian market. Hence, it is imperative to raise awareness among relevant food safety authorities regarding the occurrence of these parasites. The findings from this study should be taken into consideration for the revision of current seafood safety protocols in the country.

Distribution of the nematodes of the genus Eustrongylides (Nematoda, Dioctophymatidae) in the world

Eustrongylides spp. are nematodes from the Dioctophymatidae family, potentially dangerous for the health of mammals. The aim of this review is to describe the distribution of the Eustrongylides spp. nematode. Eustrongylidosis is a parasitic disease which is common in countries with a continental, tropical or subtropical climate. Eustrongylides are biohelminths with a complicated development cycle. The nematode development takes place in the aquatic environment and includes a wide range of intermediate, definitive, and accidental hosts. The purpose of this review is describe the distribution of Eustrongylides spp. nematodes in the global regions, describe the prevalence of infection in those regions, and identify intermediate, definitive, and accidental hosts. It was found that Eustrongylides spp. nematrodes are significantly widespread around the world. In part in North America the agent of eustrongylidosis is registered mostly among birds and fishes, but cases of humans being affected with the disease are noted as well. In South America the given disease was also registered among amphibians and reptiles. In Europe, Asia, Africa, Oceania and countries of the Far East, the disease is registered mostly in fishes, rarely – in birds. The taxonomic identification showed that some nematode species were related to certain geographic areas. For example, Eustrongylides ignotus and Eu. tubifex were mostly registered in North America, while for Europe (including Ukraine), Near and Middle East, Eu. еxcisus is a dominant species. Analysis of scientific sources showed that continents with warmer climatic conditions (South America, Asia, etc.) are characterized with a wider range of fishes, birds and reptiles which can potentially serve as hosts for the Eustrongylides nematodes.