First report of the nematode Eustrongylides sp. (Nematoda

Astyanax panamensis is a species of sardine with an omnivorous diet and is often used as a subsistence food in various regions of the country. In this study, we report for the first time the presence of larvae of the genus Eustrongylides parasitizing this species in the Darién region. Eustrongylides sp. has previously been described from Lake Gatun in two host species; however, there is no recent evidence of its distribution in other provinces of Panama, which poses a risk due to its zoonotic potential. In this study, larvae of Eustrongylides sp. were morphologically identified, with an average length of 4.3 mm, and were found in the hosts' musculature. The average number of larvae per individual was one; however, some individuals were found to be parasitized by up to three larvae simultaneously. The presence of Ciconiiformes birds in Darién suggests the possibility that the life cycle of the parasite may be sustained in this region. Further studies are needed to assess the prevalence of this and other parasites with zoonotic potential, both in Darién and in other provinces of Panama.