This study identified the different gastrointestinal parasites in traditional goat farms in Benin and evaluated their prevalence and parasite intensity in Eggs Per Gram of feces (EPG).
The high parasitism rate (96.82%) can be explained on the one hand by the traditional type of farming where animals are free and share the same grazing area and, on the other hand, by the lack of routine deworming. Similar prevalences have been reported by Salifou (1996) in Benin, Sylvia et al. (2015) in Nigeria, Ntonifor et al. (2013) in Cameroon in goats farming. The main parasites observed during this study except toxocara spp had been previously reported in small ruminants in South Benin (Salifou 1996) and the riparian camps at the Wari-Maro classified forest in North Benin (Faihun et al. 2017).
The high prevalence of coccidian oocysts, strongyles, and Strongyloides spp could be attributable to their life cycle. L3 larvae are the causative agent of the parasitic infestation. These L3 larvae undergo an automatic translation of the feces towards the grass. On the other hand, the cestodes found (Moniezia) have an obligatory intermediate host represented by certain arthropods that harbor the cysticercoid larvae. The contamination of animals requires prior ingestion of these infected arthropods. This outcome could justify that the infestation of animals by natural cycle and monoxenous parasites would be more frequent than that by parasites with an obligatory intermediate host. Furthermore, the low prevalence of whipworms among nematodes could be related to the fact that it is the embryonated egg containing the L3 larva that is the infesting form of this parasite.
Similar observations for the highest prevalences of Strongyles, Strongyloides spp or coccidial oocysts in small ruminant farms, have also been made in most tropical countries, in Middle Guinea (Barry et al. 2002), Côte d'Ivoire (Achi et al. 2003), Togo (Bastiaensen et al. 2003), Ethiopia (Dagnachew et al. 2011), Burkina Faso (Ye 2012), Cameroon (Ntonifor et al. 2013), India (Dixit et al. 2016), Nigeria (Paul et al. 2016), Laos (Gueguen et al. 2016).
Prevalences of nematodes, as well as fecal egg excretion, are significantly higher in the rainy season. Similar observations had already been made in southern Benin by Salifou (1996) and in neighboring countries, Burkina Faso (Ouattara and Dorchies 2001), and Togo (Bastiaensen et al. 2003). According to Nwosu et al. (2007), environmental conditions are generally favorable for developing, survival, and translocation of pre-parasitic stages of parasitic nematodes during the rainy season. As a result, there is an accumulation of adult worm populations in grazing animals such that maximum worm burden are recorded during the rainy season. After that, worm populations decrease in the dry season. This funding justifies a higher prevalence of animal infestation and levels of parasite egg excretion in the wet season than in the dry season. The high prevalence rates of gastrointestinal parasites observed in this study indicate the risks of economic losses for goat farmers in Benin.
The mean degrees of infestation in animals were 638.4; 424; 631; 2798 EPG in the rainy season and 101.38; 61.31; 52.43; 1022 EPG in the dry season for strongyles, Strongyloides spp, Moniezia spp, and Coccidia Coccidian oocysts, respectively. According to the severity scales, based on the EPG limits revealed by Alowanou et al. (2021), it could be concluded that infestations were severe during the rainy season for strongyles, Moniezia spp, Coccidia oocysts and moderate for Strongyloides spp. During the dry season, infestations were light for strongyles, Strongyloides spp, Moniezia spp, and severe for Coccidia. This present case requires systematic deworming of all animals in the herd for according to Bosco (2014), an infestation rate above 200 EPG already requires treatment when the fecal analysis technique is Mini-FLOTAC.
Moreover, egg production still has no relation to the population of worms harbored, as many factors influence the EPG value. Thus, an animal may only host male worms or even adults who have not yet reached sexual maturity or worms whose females are in oviposition inhibition conditions (Salifou 1996). This result shows that the animals would be heavily parasitized.
Sex had no statically significant effect on infestation with gastrointestinal parasites except Strongyloides sp. However, on all the animals studied, the proportion of females affected by nematodes was higher than males. This observation is in opposite of the conclusion of Tariq et al. (2010) who revead that both sexes are susceptible to nematode infestation. During the peripartum period, females temporarily lose their naturally acquired immunity to gastrointestinal parasites (Schoenian 2012), and therefore, they could be easily infected. Thus the slight differences in prevalence observed in females could be due to pregnant and breast-feeder females among the females sampled in this study.
The parasites prevalence and egg excretion level by age showed that adult animals were more infected with gastrointestinal nematodes than the young animales. This observation is not in agreement with the findings of some authors for whom juveniles are more susceptible to infestations than adults due to their low immunity levels (Tariq et al. 2010; Khan et al. 2010; Zeryehun 2012; Nabi et al. 2014). This difference may be related to physiological status (gestation and breastfeeding stage) and malnutrition, making adults more susceptible to infestation and excreting more eggs than non-pregnant or non-breast-feeder ones (Barry et al. 2002; Suarez et al. 2017). In addition, young animals are fed milk by their mothers until adulthood (Saidi et al. 2020), limiting their grazing exposure. Therefore they would be less infested, hence the finding of higher prevalence in adults than in young.
The higher infestation rates in Sahelian rears than in dwarf and mixed breeds indicate that they are more susceptible to gastrointestinal parasites than the other breeds. Their EPG burden is lower than that of the other breeds despite their higher infestation rates. The difference in EPG burden would be due to the limited infestation by infesting L3 larvae during grazing, as Sahelian goats were more commonly encountered in PDA1 and PDA2, which are characterized by a Sahelian climate. This hot and dry climate is not conducive to the development and survival of infesting L3 larvae.
Parasite burden in EPG were higher in PDA4 than in PDA1, PDA2, and PDA5. This outcome could be explained by the fact that free-grazing is the more common method of rearing in the dry season than in the wet season in PDA4, whereas in the other PDAs, during fieldwork in the wet season, animals were put on fixed or mobile stakes. This freedom, especially in the rainy season when conditions are favorable for the survival and translocation of the pre-parasitic stages of helminths, means that the animals would ingest enough infesting larvae on the grazing ground. As a result, the gastrointestinal burden of adult worms would be high and, consequently, a high rate of egg-laying expelled by the animals. On the other hand, the risk of infestation of the staked animals by a high burden of infesting larvae would be low even if they are fed fresh fodder. Furthermore, Trichirus spp eggs were not observed in PDA1 and PDA5 and Toxocara spp eggs in PDA1 and PDA2. This could indicate the absence of these parasites in these areas; helminthological autopsies could give more details.
The coprocultures showed that strongyles were represented by Haemonchus spp, Trichostrongylus spp, Oesophagostomum spp, Cooperia spp, Nematodirus spp, and Bunostomum spp. These results reveal that Haemonchus spp and Trichostrongylus spp, are the most dominant strongyles species in the digestive tract of small ruminants as reported by reported by Salifou (1996) in South Benin. Similar observations had also been made in several tropical countries, Burkina Faso (Ouattara and Dorchies 2001; Belem et al. 2005), Middle Guinea (Barry et al. 2002), Côte d'Ivoire (Achi et al. 2003), Togo (Bastiaensen et al. 2003), Ethiopia (Sissay et al. 2007), Nigeria (Nwosu et al. 2007). This dominance would be explained by the fact that Haemonchus spp is very prolific and can lay up to 10 000 eggs per day for several months (Raza et al. 2014). In addition, it acquires a faster resistance to synthetic antihelminthics compared to other strongyles species (Torres-Acosta et al. 2003). Haemonchus spp infection can cause severe anemia and hypoproteinemia, leading to depression, reduced productivity, and eventual animals’ death. The disease tends to be more severe in the early stage, mainly when females breastfeed with weakened immune (Sissay et al. 2007). Trichostrongylus spp is not significant but is the most constant parasite, as its presence is annual. Large infestations of Trichostrongylus spp cause inappetence, diarrhea, rapid weight loss, and death of the animal may occur rapidly (Mahieu 2014). These parasites could be associated with diarrhea mentioned by goat breeders in Benin (Hounzangbé-Adoté 2001; Idrissou et al. 2017; Challaton 2020). A specific coprological study on goats presenting diarrhea will better evaluate the share of strongyles in the pathologies responsible for diarrhea in goats.
In the dry season, the proportion of Haemonchus spp in the fecal cultures decreased and was dominated by Trichostrongylus spp. Unlike Trichostrongylus spp, the Haemonchus spp population survives during the dry season partly as hypobiotic larvae (L4) in the mucosa of the abomasum (Salifou 1996). This halt in larval growth during the dry season will result in a high larval burden (L4) and a low burden of adult Haemonchus spp worms in the abomasum. This observation results in a drop in oviposition rate and low emission of eggs in the excrement. When conditions become favorable again in the rainy season, the hypobiotic L4 larvae will continue to develop into adults capable of laying eggs and consequently an increase in the number of eggs expelled in the feces. This finding proves the dominance of Haemonchus spp and Trichostrongylus spp larvae in fecal crops in the rainy and dry seasons, respectively. Haemonchus spp would thus preserve itself as a biological species in nature by using this strategy of increasing its prevalence on animals and inhibiting its development at the L4 larval stage, in particular, severe climatic periods of the year (Belem et al. 2005). Given the adverse effects of these two parasites on goats and the resistance to synthetic anthelmintics, special attention should be given to them in controlling gastrointestinal parasites of small ruminants.