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 -resistant isolate of the pig nematode, Oesophagostomum dentatum. The experiment had three steps. In the first step, LD50 values for pyrantel of the two isolates in the assay were established. In the second step, susceptible and resistant worms were mixed in various proportions prior to exposure to a fixed concentration of pyrantel and thereafter assayed. The inhibition of migration showed to be linearly correlated with the proportion of resistant worms in a sample. In step three, this line was used as a standard curve to predict the number of resistant worms in samples from pigs infected with mixed samples of susceptible and resistant larvae.