Host specificity of Haemonchus spp. for domestic ruminants in the savanna in northern Ivory Coast.

Three Haemonchus species (Haemonchus contortus, Haemonchus placei and Haemonchus similis) live in sympatry in the savanna of North Côte d'Ivoire. Four domestic ruminant hosts (zebu-cattle, taurine-cattle, sheep and goats) share the same pastures throughout the year. Our post-mortem data imply that a Haemonchus spp. circulation exists among the different hosts species in the savanna of North Côte d'Ivoire. Under field conditions, mixed congeneric infections were the rule except in sheep where mono-specific H. contortus infections were the most frequent. The associations H.contortus+H.placei and H.placei+H.similis were dominant in goats and in cattle, respectively. In the populations examined, triple infections occurred in 11.5% of zebu-cattle and 29% of the taurine-cattle. Considering the intensities of infections, H. contortus was the main Haemonchus species of sheep and goats whereas H. similis was very rare in these host species. About 10% of the worms recovered in goats belong to the H. placei species. In cattle, H. contortus was very rare. H. placei was the dominant species in zebu-cattle (58.7% of the identified worms) and in taurine-cattle (73.9%) nevertheless, the proportion of H. similis was higher in zebu-cattle (38.6%) than in taurine-cattle (21.3%). Only few hybrids between H. placei and H. similis were found. The importance of such Haemonchus spp. circulation is discussed.