The increasing reports of heartworm-positive dogs in communities along the Mississippi River have spurred research into the preventative drugs’ failures and whether there could be heartworms that have become genetically resistant to the medications.
“We always thought it was a compliance issue – that not every medicine works in every dog or that an owner thought they gave their dog the pill but actually forgot or the dog threw up the medicine,” said Mark Russak, director of Student Affairs at Mississippi State University’s College of Veterinary Medicine.
“But we’re seeing more cases than ever before,” he said. “It’s my gut feeling that it’s resistance.”
Scientists had believed that because of the short life cycle of a heartworm, it’s not genetically possible for them to become resistant to the poison used to kill them, American Heartworm Society President Sheldon Rubin said.
But newer research, led by Byron Blagburn, a veterinary medicine professor at Auburn University, suggests there are reports of heartworm positive dogs that can’t be explained by owners failing to give preventative drugs properly.
Blagburn presented his findings last week at an American Heartworm Society’s symposium in Memphis. He could not be reached for comment.
If resistance is proven, it could be bad news for pet owners as well as manufacturers of popular heartworm preventatives.