Endoparasites in yellow anaconda (Eunectes notaeus) in the wild through coproparasitological tools

Snakes constitute the largest group of reptiles and play a crucial role in food chains, contributing to the balance of ecosystems. Despite this, they remain the least studied reptiles in the wild. This study aimed to identify the parasitic forms present in a wild population of yellow anacondas (Eunectes notaeus) from La Estrella marsh, Formosa, Argentina, through faecal matter analysis using flotation, sedimentation, and staining techniques. Between 2019 and 2023, 150 faecal samples were collected from the "Yellow Anaconda Management Program" in Fortín La Soledad. The samples were processed using the qualitative modified Ritchie sedimentation technique (ST), Willis flotation technique (FT), and Kinyoun staining. Parasitic forms belonging to four taxa were recovered. The prevalence of parasitism (P) was 64 % (ST) and 38 % (FT), and the following taxa were detected: Crepidobothrium sp. (Cestoda) eggs (P = 44.66 % ST and 24.66 % FT), Telorchis sp. (Digenea) eggs (P = 26 % ST and 18 % FT), and Nematoda larvae and eggs (P = 12 % ST and 2.66 % FT). Also, coccidia were detected using the FT (P = 1.33 %). The Ritchie method was more effective than the Willis method, specifically in recovering Crepidobothrium eggs and nematode larvae, while the Willis method was the only one that detected coccidia. No Cryptosporidium oocysts were found. In this study, the diagnosis of parasitic forms represents a valuable contribution to the ophidian parasitology, as well as an evaluation of the effectiveness of the techniques used.