A recent article in the journal of Veterinary Parasitology has reported a new treatment for dogs that are determined to be heartworm positive. Currently, the only drug registered for adulticide therapy against canine heartworm is an arsenic derivative. However, treatment is often followed by severe pulmonary thrombosis following death of the entire worm population in a short period of time.

The reported study was done on 11 heartworm positive dogs (8 were from a local animal shelter) ranging in age from 3 to 10 years old. Dogs were treated with a combination of the antibiotic doxycycline and ivermectin (HEARTGARDĀ®). Each animal received doxycycline at 10mg/kg daily for 30 days and ivermectin (standard dose for the weight of the dog) every 15 days for 6 months. At the end of the study, 100% of the dogs were negative for circulating microfilaria. The therapy eliminated adult worms rapidly with no reported side effects.

The benefit of opting for this treatment is third-fold. First, this combined therapy has fewer detrimental side-effects for the heartworm positive animal. Second, this treatment can be administered by the owner (under veterinary supervision). And third, this gives rescue groups a relatively inexpensive option for treatment of infected dogs.

I would encourage owners to discuss this treatment option with their veterinarian. A complete copy of this study can be found at:

2010. Veterinary Parasitology. A Combination of Doxycycline and Ivermectin is Adulticidal in Dogs with Naturally Acquired Heartworm Disease (Dirofilaria immitis). G. Grandi, C. Quintavalla, A. Mavropoulou, et al. Vol. 169, pgs 347-351.

By Dr. Michelle Raisor, Ph.d