ECOLOGICAL, MORPHOLOGICAL AND GENETIC-CHARACTERIZATION OF SYMPATRIC HAEMONCHUS SPP PARASITES OF DOMESTIC RUMINANTS IN MAURITANIA

The 4 species of ruminants (dromedary, zebu cattle, Sheep and goat) in arid areas of Mauritania harboured Haemonchus spp. as the most freque nt internal parasite. This was a rare situation where the 3 putative s pecies, H. longistipes (dromedary), H. placei (zebu cattle) and H. con tortus (sheep and goat) occurred sympatrically. The study was undertak en on hosts slaughtered at the Nouakchott abattoir, on the basis of mo nthly collection of worms. The environment was very unfavourable to H. placei and unfavourable to H. contortus, as intensity of infection re mained low throughout the year, whereas infection in the dromedary was 10 to 20-fold higher. The survival strategies during the long, dry se ason were different: the surviving stages were either 4th-stage larvae in digesta (dromedaries), 4th-stage larvae either in digesta or mucos ae (cattle), or 4th-stage larvae in mucosae and few adults (sheep and goats). The prolificacy of female worms, indicative of the potential t o contaminate pastures, was similar for all Haemonchus spp. in the rai ny season. H. longistipes behave differently during the pre-rainy seas on as no increase of prolificacy could be demonstrated as observed in the other species. Traits of vulvar morphology are considered as marke rs of ecological adaptation and were studied. The knobbed and smooth f emale morphs (in equal proportions) were the most frequent in H. longi stipes, the knobbed morph outnumbered the other morphs in H. placei, a nd all 3 morphs were present in sheep and goats with the linguiform fo rm being predominant. Genetic characterization of the 3 species was pe rformed by means of Random Amplified Polymorphic DNA (RAPD). Three gro ups were obtained from analysis of these data: 1 group with individual s of H. contortus, 1 group with individuals of H. placei, and 1 group with, individuals of H. longistipes. This indicated that, although the 3 species were valid, H. contortus and H. placei were more similar. I ntraspecific variability was 2-fold higher in H. contortus than in the 2 other species. The ecological, morphological and genetical studies showed that H. longistipes, H. placei and H. contortus could be arrang ed in increasing order of variability.