STUDIES ON MULTISPECIFIC RESISTANCE OF GASTROINTESTINAL NEMATODES TO BENZIMIDAZOLES ON DAIRY-GOAT FARMS

Multispecific resistance to benzimidazoles was studied in three select ed farms. These farms had bred dairy goats for more than 15 years. The helminths were introduced with the goats at the establishment of the farms which afterwards remained isolated. Nematode resistance could th en be related to their own management practices. Faecal egg count test s and egg hatch assays were performed to assess intensity of resistanc e. The generic (infective larvae in faecal cultures) and specific rich ness (adult worms) were assessed. The resistant species were Trichostr ongylus colubriformis, Teladorsagia circumcincta, Haemonchus contortus and Oesophagostomum venulosum. Faecal egg count reduction tests and e gg-hatch assays did not match exactly. Faecal larval counts after trea tments gave a distorted picture of multispecific resistance: Haemonchu s and Oesophagostomum were very largely over represented. The number o f species found in the three farms was relatively low compared with ot her reports in goat farms of the area. This reduction of diversity mig ht also be due in part to characteristics of breeding management and h istory (use of permanent pasture and introduction of goats at the esta blishment of farm).