Dogs develop heartworm disease in response to live and dead heartworms. Disease control should emphasize infection prevention by regular administration of preventatives and surveillance testing. Two excellent heartworm preventatives, ivermectin and milbemycin oxime, have been the mainstays of infection prevention for approximately 20 years.1 Recent research has established that these macrolide drugs, especially ivermectin, have some adulticidal effect when given at 3 to 7 months following infection with third-stage larvae of Dirofilaria immitis.2–,6 This “pearl of veterinary practice” will summarize our recently published research on how the macrolide-induced killing of young heartworms affects the host dog, possibly your canine patient.7
Heartworm disease starts 3 months after infective larvae are deposited at the feeding puncture wound by a carrier mosquito [Figure 1]. At 70 to 90 days, young adult worms arrive in the smaller pulmonary arteries, especially in the caudal lung lobes.8,9...
