VARIABILITY IN SUSCEPTIBILITY TO ANTHELMINTICS OF THE LUNGWORM MUELLERIUS-CAPILLARIS 1ST-STAGE LARVAE - RELATIONSHIP TO DAIRY-GOAT FARMS AND PREVIOUS EXPOSURE TO FEBANTEL TREATMENT

Seven dairy-goat farms, located in central, western France, were studi ed in order to assess the variability in susceptibility of the lungwor m Muellerius capillaris first-stage larvae (L1) to 3 different anthelm intics in relation to farm origin, by means of motility tests. The mot ility tests were performed by mixing larval suspensions with pyrantel (PYR), thiabendazole (TBZ) or ivermectin (IVE) solutions (3 concentrat ion x 3 incubation durations). The same anthelmintic tests were repeat ed 7 and 21 d after febantel (probenzimidazole) treatment of the goats . Before the treatment of goats, the average ratio (x 100) of L1 motil ity compared with control were very different for the 3 anthelminthics : 44, 30 and 59, respectively for TBZ, PYR and IVE. The ratios of L1 m otility were the same at days 7 and 21 after the treatment of goats. T he susceptibility of L1 to anthelmintics varied a great deal from 1 fa rm to another when goats had not been previously treated, whereas L1s from the same farms were the same after treatment of goats. The occurr ence of different motilities of L1 with the anthelmintic tests from 1 farm to another should be related to the existence of different popula tions of M capillaris. The L1 motilities were reduced after anthelmint ic treatment of goats suggesting a temporary effect on populations of M capillaris females shedding L1.