Effect of development of resistance to benzimidazoles, salicylanilides and ivermectin on the pathogenicity and survival of Haemonchus contortus
Scott, E.W.; Armour, J.
Veterinary Record 128(15): 346-349
1991
ISSN/ISBN: 0042-4900 PMID: 2063534 Document Number: 380738
Two groups of 6 lambs were infected either with an anthelmintic-susceptible strain of H. contortus or with a strain resistant to benzimidazoles, ivermectin and salicylanilides. The pathogenicity of the 2 strains of parasite was compared by monitoring the development of anaemia, changes in plasma proteins and abomasal damage in the 2 groups of lambs. There were no significant differences between the groups, suggesting that the development of resistance to several anthelmintics did not correlate with an increase in the pathogenicity of the parasites. Furthermore, the establishment rates and egg production of the susceptible and resistant parasites were similar. However, fewer of the eggs of the resistant parasites survived and developed at a variety of temperatures.