Seasonal Variation of Nematode Parasites and Condition Factor in the Catfish Clarias anguillaris from the Bandama River at N’Denou (Côte d’Ivoire)

The African catfish Clarias anguillaris is widely exploited in aquaculture due to its high performance and nutritional value, thereby contributing to food security and job creation. However, in the Bandama River at N’Denou, an area subjected to anthropogenic activities, this species is exposed to parasitic nematodes that may affect its production. No parasitological study had previously been conducted in this area. The present study aimed to inventory nematode species, analyze their seasonal diversity, and assess their impact on the condition factor of C. anguillaris. A total of 560 fish were collected between April 2024 and March 2025. Parasites were searched for, identified, and counted using standard methods. Chi-square (χ²), Mann–Whitney (U) and Kruskal–Wallis (K) tests were applied. Nine species were identified: Paracamallanus cyathopharynx, Procamallanus laeviconchus, Contracaecum sp., Falcaustra petrei, Rhabdochona congolensis, Spirocamallanus spiralis, Brevimulticaecum heterotis, Camallanus polypteri, and Anisakis sp. The highest prevalence (P) and mean intensity (MI) were observed in the intestine, particularly for P. cyathopharynx, P. laeviconchus, and F. petrei. During the dry season, infestations reached their peak, with high values recorded for P. cyathopharynx (P = 97.92%; MI = 23.32 ± 2.2), P. laeviconchus (P = 91.84%; MI = 23.38 ± 2.1), and F. petrei (P = 85.11%; MI = 19.39 ± 1.7). Shannon–Weaver (H′ = 3.54 bits/ind), Simpson (D = 0.86), and evenness (E = 0.86) indices indicated high diversity during this period. The condition factor of parasitized fish (K = 0.27 ± 0.01) was significantly lower than that of non-parasitized fish (K = 0.68 ± 0.02), indicating a negative impact of parasitic infestations on the physiological state of individuals. This study characterizes the parasitic fauna of C. anguillaris. It also highlights periods of vulnerability of the species and the deleterious effects of parasitic nematodes. These findings provide a solid scientific basis for the development of sustainable management strategies aimed at reconciling the conservation of this fishery resource with the improvement of local livelihoods.