We've Got Boots on the Ground

Parasites are becoming immune to our deworming drugs.

Resistance develops when the recommended dose of dewormer does not kill 100% of the parasites inhabiting an animal. This process of selection allows resistant survivors (those not killed by the dewormer) to mate with other resistant worms and subsequently pass resistant genes onto their offspring. Resistance becomes a clinical problem when there are a high number of resistant worms within the treated population leading to treatment failure and clinical disease. The rate at which modification to the parasite gene pool occurs within a given population varies depending upon a number of factors including: the frequency of exposure to a particular class of anthelmintic, the immune status of the individual animal and the size of the parasite population in refugia (the population that has never be exposed to anthelmintics).