Study of genetic variability of Haemonchus contortus in alpine Italian ruminant populations

Haemonchus contortus, a generalist abomasal nematode, has been shown to affect the livestock productivity in domestic ruminants and the health status of wild hosts. Molecular techniques are useful to investigate genetic differentiation in parasite populations, host specificity and evolutionary history of parasite species. In total 77 adult males of H. contortus collected from isolates of 3 different Italian alpine areas were used for partial mitochondrial NADH dehydrogenase subunit 4 gene (ND4) analysis. Sequences were compared with 49 GenBank sequences, obtained from sheep in United States. On the basis of the results on ND4, a subset of isolates was examined also for Internal Transcribed Spacers 1 and 2 (ITS1 and ITS2) nuclear genes. Analyses on ND4 gene showed 2 clusters, in which isolates appear from each considered host species (chamois, roe deer, goat, sheep) and geographical origin. American sequences are aligned in only one group. A high intra-specific variability was pointed out even in each cluster. However molecular data on ITS1 and ITS2 have not confirmed the mitochondrial results. For this reason, to assess if it could be referred to an ancestral polymorphism or due to host-adaptation mechanisms, a further work using microsatellites is in progress. Moreover, the low host-specificity and the high gene flow among the H. contortus populations, led us to further check the a priori assumption that domestic sheep is the reservoir of this parasite. It arises the importance of managing parasite infections of domestic flocks to prevent spill-over to wildlife.