Canine · Cardiovascular · Parasitology
Canine heartworm disease
Dirofilaria immitis lives in the pulmonary arteries, not the heart chambers, except in caval syndrome. Adulticide therapy requires strict exercise restriction.
Transmission is by mosquito, with L3 maturing over roughly six months to adults in the pulmonary arteries, causing endarteritis, pulmonary hypertension, and eventually right heart failure. Antigen testing detects adult females; microfilaria testing should accompany it. Doxycycline reduces the Wolbachia endosymbiont and worm pathogenicity before melarsomine, which is given in the three-dose protocol. Exercise restriction across the entire treatment period is the single most important owner instruction, because thromboembolism from dying worms is the main cause of death. Caval syndrome, with hemoglobinuria and a tricuspid murmur, needs mechanical worm removal. Year-round macrocyclic lactone prevention with annual testing is the standard.