First morphological and molecular characterization of the genus Eustrongylides nematode larvae infecting fish in the Brazilian Amazon

While birds are the definitive hosts of nematodes of Eustrongylides spp., other vertebrates, such as fish, amphibians and reptiles, represent intermediate/paratenic hosts. Despite their zoonotic potential, however, the taxonomic characterization of the larval stages of fish parasitic nematodes in the Brazilian Amazon remains limited. The present study aims to describe the morphological and molecular characteristics of Eustrongylides sp. found parasitizing the musculature of Hoplia malabaricus from the Amazon Basin, in the region of Santarém, in the state of Pará, Brazil. In addition to presenting a new geographic record, the present study morphologically and molecularly characterizes Eustrongylides sp. larvae in the Brazilian Amazon using the 18S ribosomal gene. As this nematode can be considered a potential emerging cause of disease, it is important to use molecular markers to improve diagnosis, in addition to describing new species and evaluating the genetic distribution of Eustrongylides populations in the Brazilian Amazon.