A combination of doxycycline and ivermectin is adulticidal in dogs with naturally acquired heartworm disease (Dirofilaria immitis)

Canine heartworm disease is caused by infection with Dirofilaria immitis, a filarial nematode that resides in the pulmonary arteries and occasionally in the right heart chambers of infected dogs. Here the authors evaluated the effect of a combination of doxycycline (10 mg/kg/sid for 30 days) and ivermectin-pyrantel (6 mu g/kg to 14 mg/kg every 15 days for 180 days) on microfilariemia, antigenemia and parasite load at echocardiography in naturally infected dogs from an endemic region of Italy. Dogs were examined monthly for 6 months and followed-up 4 months later. One hundred percent of dogs became negative for circulating microfilariae by day 90, while 8/11(72.7%) of dogs became antigen-negative by day 300. Of the 7 dogs that were positive for visualization of parasites at echocardiography, 6(85.7%) became negative by day 300. Treatment was well-tolerated by all dogs. These results suggest that a combination of doxycycline and ivermectin is adulticide in dogs with D. immitis. (C) 2010 Elsevier B.V. All rights reserved.