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ARTICLES

Vol. 15 No. 2 (2026): Rev. Arg. Parasitol.

First record of Contracaecum sp. (Nematoda: Anisakidae) larvae in Eunectes notaeus with a hypothesis on the role of yellow anaconda in the parasite’s transmission

Submitted
July 26, 2026
Published
2026-10-24

Abstract

Species of Contracaecum (Anisakidae) are widely distributed nematodes whose life cycle involves aquatic invertebrates and fishes as intermediate and/or paratenic hosts and piscivorous birds and mammals as definitive hosts. Although third-stage larvae have occasionally been reported from reptiles, no records of Contracaecum larvae have been documented in snakes of the genus Eunectes. This study documents for the first time the occurrence of Contracaecum third-stage larvae in the yellow anaconda, Eunectes notaeus, from Bañado La Estrella, Formosa Province, Argentina. One hundred and fifty adult E. notaeus (> 160 cm) collected during the Yellow Anaconda Management Program between 2019 and 2023 were examined for helminths. Larvae recovered from the gastric serosa were studied using light microscopy and scanning electron microscopy and identified based on morphological characters. A total of 196 third-stage larvae of Contracaecum were recovered, with a prevalence of 33.33%, a mean abundance of 1.30, and a mean intensity of 3.92. There were no statistically significant differences in prevalence between years. This study represents the first record of Contracaecum larvae infecting E. notaeus and the first for the genus Eunectes. The larval localisation and the position of these snakes in the trophic webs lead to hypothesising that small specimens of this semi-aquatic species can act as paratenic hosts, potentially contributing to the maintenance of Contracaecum within Neotropical wetland food webs. These findings expand the known host range of the genus and provide new insights into the ecological role of reptiles in anisakid transmission cycles.

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