Arid and semi-arid zones, although relatively poor in species, are home to a range of iconic antelopes adapted to the constraints of these extreme environments [1]. These species are key components of Saharan-Sahelian biodiversity, the region to which Senegal belongs. The natural dynamics of these populations are severely compromised by habitat degradation, poaching, human activities, climatic events such as droughts, and disease. The majority of infectious diseases, which affect public health, livestock, and food security, originate from wildlife [2][3]. Diseases such as parasitic infestations can be transmitted directly or indirectly through contaminated water, soil, meat, or excrement, affecting other wild and domestic animals, or humans [4]. Africa is the continent that has lost the greatest number of higher vertebrate species, particularly birds and large mammals, compared to other Palearctic regions [1]. At the end of the 1980s, Gazelladorcas was still found in all the countries of the Sahel-Saharan strip, with the exception of Senegal. However, its numbers had been substantially reduced, and it was then considered threatened or endangered throughout the region. Oryxdammah formerly residing in the semi-desert areas of Africa, is now a species whose survival depends on captive populations. The last wild populations disappeared in the 1970s and 1980s. Faced with this situation, Senegal has undertaken reintroduction and conservation programs aimed at safeguarding these threatened or endangered species. In the context of reintroducing these species, the Special Wildlife Reserve of Gueumbeul was chosen to host the first antelope’s populations. The internationally recognized Gueumbeul Reserve serves primarily as an acclimatization and breeding center for Sahelian-Saharan wildlife reintroduced to Senegal. It is a cornerstone of national initiatives to restore species extinct in the north of the country. The first reintroductions involved the Gazelladamamhorr in 1984, followed by the Oryxdammah in 1999 and the Gazelladorcas in 2007. However, the long-term survival of these wild ungulates depends on monitoring their health status, an aspect that is very poorly documented in Senegal. Elsewhere, many studies have emphasized the importance of regularly monitoring parasites and parasitic diseases in wild ungulates [2][4]-[10]. It is in this context that this study was conducted in order to contribute to improving knowledge about helminth infections of antelopes raised in the Special Wildlife Reserve of Gueumbeul. The aim was to identify the helminth species isolated from fecal matter, to determine the infestation rates and to assess the severity of the infestation.

The aim of this study was to identify parasitic species and determine infestation rates and levels of infestation by gastrointestinal parasites in captive and semi-captive Gazelladorcas and Oryxdammah in the Wildlife Reserve of Gueumbeul. Fecal samples, stored at +4˚C, were examined microscopically within 24 to 48 hours to detect eggs and larval forms of helminths.

Enrichment of the feces in a dense sodium chloride solution allowed for the identification and counting of helminth eggs. Identification was based on egg morphology, and the level of infestation was assessed by determining the number of eggs per gram of feces. The results showed that 75% and 68.6% of the samples examined, from Oryxdammah and Gazelladorcas respectively, harbored one or more helminths. Oryxdammah raised in semi-captivity had a higher infestation rate than captive-bred Gazelladorcas. Several authors have reported that animals living in the wild often exhibit greater parasite diversity and load than those kept in captivity. Increased exposure to intermediate hosts and more favorable environmental conditions would contribute to parasite development and increase the likelihood of infestation of definitive hosts [16]. However, [17] and [18] reported low infestation rates and a high diversity of helminths in mountain gazelles (Gazellagazella) of Hatay in Türkiye. The study revealed infestation of both Oryxdammah and Gazelladorcas by nematodes, trematodes, and cestodes. Among the nematodes, strongyles were the most common. Regarding cestodes, only Monieziaspp. was observed in the samples, and Dicrocoeliumspp. among the trematodes. The diversity of parasitic species observed is comparable to that reported in studies of captive-bred Gazelles populations [19]. The results reveal that nematodes are predominant compared to cestodes and trematodes. Studies have reported similar results, suggesting a higher frequency of nematodes [11]. The high frequency of nematodes is thought to be due to the fact that many of these parasites have direct life cycles and are easily transmitted through the ingestion of larvae present in grass and soil. Furthermore, studies on semi-captive populations of Gazellasubgutturosa have reported infestation by helminths such as Dicrocoeliumdendriticum, Marshallagiamarshalli,Skrjabinemaovis, and Trichurisspp. [7][20]. In addition, strongyle infestations in captive populations of Gazellaleptoceros in Belgium have been reported by [21]. Besides Strongyles, infestations by helminths such as Nematodirusspathiger, Tricostrongylusvitrinus, and Ostertagiaostertagia have been reported by [21][22]. The infestation rate was significantly higher during the rainy season, in August and September. The finding did not agreement with the report of [23][24], who reported that seasonal variation in parasitic infection among the zoo animals in the garden. This result can be explained by the evolution of the climatic conditions in the study area during the two seasons. Indeed, the temperature and humidity are favorable to the development of free-living parasite stages. During this period, Oryxdammah are more exposed to ingesting these parasite forms in the pastures. The semi-captive grazing of Oryxdammah would explain their higher parasite load compared to Gazelladorcas raised in captivity in enclosures. However, it should be noted that their habitats are not regularly cleaned, which could promote the development of helminth eggs and their subsequent infectiveness. Furthermore, although their infestation rate is high (68.6%), their average OPG is less than 600, indicating a less severe level of infestation compared to the Oryxdammah. Furthermore, [18] reported a low number of parasite eggs on fecal samples from Gazellagazella from Hatay, Türkiye. Indeed, Gazelladorcas are regularly dewormed upon capture and transfer to enclosures, treatments which are effective in maintaining the average OPG below 600. The anthelmintics commonly administered to the gazelles appear to have blocked the development cycle of the Strongyles. Consequently, few adult, mature Strongyles are present in their digestive tracts, with a low number of eggs laid and excreted. In contrast, the Oryxdammah are raised in semi-captivity and therefore do not benefit from deworming treatments like the gazelles. Moreover, the Oryx have more contact with other wild animals in the reserve. They share the same grazing lands and watering holes with wild herbivores during the rainy season. This coexistence may have increased the transmission frequency of certain parasites. In contrast, the Gazelles are more isolated from these wild animals and are fed peanut hay harvested from their enclosures, which could explain their lower OPG compared to the Oryx. The latter are more susceptible to developing clinical signs related to a high parasite load, such as diarrhea, anemia, submandibular edema, and weight loss.

Factors such as shared water sources and grazing lands can promote the parasite life cycle and increase the likelihood of parasite transmission. Many parasites isolated from wild animals can cross the species barrier to infect humans and domestic animals [25]. In our study, Toxocara eggs would originate from wild carnivores in the reserve and could be a risk to staff. An intermediate host is not required for this infection, direct transmission can occur through fecal contamination [26]. However, it should be noted that our sampling method had limitations. Indeed, the samples were not individual in the Gazelles and in the Oryx. Furthermore, in the Gazelles, the population size was small compared to the number of fecal samples obtained by ground collection.

Parasitic infestations have a direct impact on the welfare of wild animals. Performing coprological examinations of feces from the OryxDammah and Gazelladorcas to detect and identify gastrointestinal parasite species is crucial for the conservation of these species. This study contributes to improving knowledge about these helminths in endangered gazelles raised in captivity and semi-captivity in the Special Wildlife Reserve of Gueumbeul. It is the first study on helminths in these wild animals in Senegal. Despite methodological limitations, high infestation rates, a diversity of parasite species, and a high parasite load were observed in these wild animals, particularly in the Oryx compared to the Gazelles. However, individual sampling would have allowed for an even broader parasitic spectrum and a better assessment of parasite dynamics. This study represents a first step towards identifying zoonotic helminths in Oryx and Gazelles. Studies focusing on different wild species, individually sampled, would improve the accuracy of the results obtained. In this regard, this study highlights methodological aspects that need improvement in future research on the reserve’s wild animals. We suggest that deworming treatments be carried out during the dry season when the Oryx receive supplemental feed. After estimating the total weight of the subjects, the appropriate dose of anthelmintic could be mixed with the concentrated feed served. For gazelles, treatment could be administered during capture and transfer periods.

Thanks are due to the staff of the Special Wildlife Reserve of Gueumbeul who voluntarily agreed to participate in the study.