Use of a migration assay for the separation of adult pyrantel-susceptible and -resistant Oesophagostomum dentatum

A migration assay was used to separate a pyrantel-susceptible and -resistan t isolate of the pig nematode, Oesophagostomum dentatum. The experiment had three steps. In the first step, LD50 values for pyrantel of the two isolat es in the assay were established. In the second step, susceptible and resis tant worms were mixed in various proportions prior to exposure to a fixed c oncentration of pyrantel and thereafter assayed. The inhibition of migratio n showed to be linearly correlated with the proportion of resistant worms i n a sample. In step three, this line was used as a standard curve to predic t the number of resistant worms in samples from pigs infected with mixed sa mples of susceptible and resistant larvae. (C) 2000 Elsevier Science B.V. A ll rights reserved.