In early April, we ran an article titled “Detecting and preventing drug-resistant parasites,” based on an FDA publication outlining possible causes for the development of resistant parasites and potential management solutions.

The paper focused, in part, on the concept of “refugia,” which is a portion of the parasite population not targeted for treatment. The strategy involves creating a “refuge” for some parasites by leaving them untreated. The idea is to maintain a population of drug-susceptible parasites to dilute the population of resistant ones. The authors suggest, for example, that treating just half the herd at one time could reduce parasite loads while helping retain the population’s susceptibility to anti-parasite drugs.

Knowing drug resistance in parasites is a complex issue with no clear consensus among the experts on causes or prevention, we asked for responses from veterinarians and parasitologists to the FDA’s conclusions and recommendations.

Veterinary parasitologist Lou Gasbarre offered some insightful comments that we posted to this site. We’d like to hear from more experts on this issue and share their insights with readers. Please post your comments here or e-mail me at Thanks.