Seasonal prevalence and in vitro sensitivity to macrocyclic lactones and imidazothiazoles in gastrointestinal nematodes in captive Addax nasomaculatus antelope

The antelope Addax nasomaculatus is a wild ruminant that is critically endangered and difficult to manipulate in vivo. There is limited information regarding the gastrointestinal nematode genera (GIN) present in the species and their pharmacological sensitivity to antiparasitic drugs. This study aimed to evaluate the seasonal prevalence of gastrointestinal nematode genera in the addax antelope and its relationship with in vitro sensitivity to macrocyclic lactones and imidazothiazoles in captivity. Fecal samples were collected monthly over a one-year period (n = 10) from a population located in Parque Lecocq (Montevideo, 34°47′S, 56°20′W) and cultured to obtain larvae 3 (L3). Larval motility was determined using a Microtracker, which was used to establish the sensitivity of L3 to seven dilutions in 1.6 % DMSO of ivermectin (range 0.5 to 32 μM), moxidectin (range 0.5 to 32 μM), and levamisole (range 1.56 to 100 μM), and the surviving L3 genera were identified by morphological traits. Haemonchus sp. predominated in summer, and Trichostrongylus sp. in winter. Overall, the effectiveness was lower than 25 % for ivermectin and moxidectin and greater than 90 % for levamisole, except during winter when Trichostrongylus sp. predominated. This study describes a system for indirect monitoring of in vitro pharmacological sensitivity in GIN parasite populations present in Addax nasomaculatus, which simultaneously seems promising for therapeutic development in other wildlife species. The results of this research contribute significantly to the understanding of deworming management in wildlife species and provide an alternative tool for research on parasite control in other wildlife species.