How to stop breeding resistant heartworms

Clarke Atkins, DVM, DACVIM (cardiology), at the 15th Triennial Heartworm Symposium in New Orleans (Video still courtesy of American Heartworm Society)He's a veterinarian who digs macrocyclic lactones-you know, all those good parasite preventive "mectins": ivermectin, abamectin, doramectin, eprinomectin, selamectin.

In a new video filmed in September at the 15th Triennial Heartworm Symposium in New Orleans, Clarke Atkins, DVM, DACVIM, professor emeritus at North Carolina State University, says it's the right drug at the right time with the right testing that will help reduce heartworm resistance to medication.

"Veterinarians need to realize that the use of macrocyclic lactones is imperative," Atkins says. "They need to be used year-round, and we need to test [patients] yearly."

The problem, veterinarians know, is in the gap-when a dog misses a heartworm preventive dose and is infected.

"In areas in which the exposure potential is massive, like the Deep South where there are lots of mosquitoes and a very high mosquito infectivity rate, it's even more important," he says. "I believe under those circumstances that small errors are compounded. So a five-day lapse [in administering heartworm preventive] in North Carolina is not tolerable in Baton Rouge at certain times of the year."

What's the trick? Testing and the right antibiotic before a new heartworm preventive dose.

"To prevent drug resistance, we need to make sure that dogs that are infected that go on a macrocyclic lactone have clearance of the microfilariae," Atkins counsels. "I believe really strongly in doxycycline for this. It gets rid of the microfilariae and renders them noninfectious. You can protect the dog with a macrocyclic lactone but not worry about producing greater resistance."

Watch Atkins deliver his heartfelt heartworm advice to veterinarians below: