Recent studies show that a strain of heartworm has developed that appears resistant to preventative medications. The Companion Animal Parasite Council (CAPC) has identified strains of heartworm in the Mississippi Delta region that appear in dogs who have been taking heartworm preventives. None of the major macrocyclic lactone (ML) product class of heartworm medications (ivermectin, selamectin, milbemycin oxime, and moxidectin) have proven effective in warding off this particular strain of the parasite, causing the CAPC to reevaluate their current stance on how to best treat for heartworm disease.
What this Means for Your Pet
The CAPC is now calling for a permanent cessation on using the “slow-kill” form of treatment (i.e., using heartworm preventatives to kill off an existing heartworm condition) and states that pet parents should seek a more aggressive form of treatment (such as Immiticide injections). It is thought that the “slow-kill” style of treatment has given heartworms a prolonged exposure to a non-lethal amount of drugs, thereby giving surviving parasites the opportunity to build up a resistance.
Heartworm Prevention Methods
This does not mean that current preventative measures are no longer relevant or necessary, says the CAPC. Quite the contrary -- now, as ever, is it of peak importance to make sure your pets are protected from heartworm disease. Prevention with heartworm medications is always the best option when it comes to this tricky and deadly disease.
Also as important as ever is yearly heartworm testing. Having your pet tested for heartworm at least once a year is the only way to be certain that your pet remains healthy. You may also consider limiting your pet's exposure to mosquito-rich areas, as mosquitoes are the primary transmitters of heartworm disease.
Learn more about heartworm testing.