Biology and Management of Anthelmintic Resistance
Ray M. Kaplan
from: Essentials of Veterinary Parasitology (Edited by: Hany M. Elsheikha and Naveed Ahmed Khan). Caister Academic Press, U.K. (2011)
Anthelmintic resistance is defined as a heritable genetic change in a population of worms that produces an alteration in the chemical sensitivity of that population. This change enables some individual worms in that population to survive drug treatments that are generally effective against the same species and stage of infection at the same dose rate. In practical terms anthelmintic resistance is present in a population of parasites when the efficacy of the drug falls below that which is historically expected, when other causes of reduced efficacy have been ruled out. These types of genetic changes occur slowly, usually over many years, and are the direct result of natural selection on parasite populations in response to drug treatments. Precise molecular mechanisms have not been clearly elucidated for any of the anthelmintics, but some important mutations have been identified that are involved in resistance to benzimidazole drugs read more ...