Heart worm (heart worm disease) or dirofilariosis is a parasitic potentially fataldisease of dogs and cats. It is caused by the nematode Dirofilaria immitis. The adult nematode lives in the lung arteries and right ventricle.


Dirofilaria immitis adults reach maturity and sexually reproduce in the pulmonary arteries and right ventricle. Adult males are around 15cm in length, and females are around 25cm1. After mating, female worms release larvae known as microfilariae (or L1) into the circulation. When a mosquito takes a blood meal from the infected dog or cat, microfilariae are ingested. Mosquitoes are true intermediate hosts for Dirofilaria immitis, since microfilariae require a period of maturation to L2 then L3 in the vector..
Once matured, L3 in the mosquito migrate to the labium, from which they erupt onto the host’s skin as the mosquito feeds. Larvae then migrate into the bite wound and, as most dogs are highly susceptible to heartworm disease, most L3 then establish infection. It takes 2-3 days for L3 to moult to L4, which remain in the subcutaneous tissues for up to two months before becoming young adults (L5) and migrating to the pulmonary arteries.


I dogs, historical findings at the time of presentation can vary. Some animals are asymptomatic, or cough only occasionally. More obvious signs may be seen depending on the severity of disease. Generally, the onset of heartworm disease is insidious, and clinical signs are related either to a high parasite burden, or to an allergic response to the parasite. Affected dogs most often show coughing, and dyspnoea/tachypnoea, exercise intolerance, loss of condition and syncope may also be seen. In severe cases the pulmonary vessels may rupture, leading to haemoptysis or epistaxis. There is a tendency for signs to only manifest during exercise, and so patients with a sedentary lifestyle may never show overt disease. Right-sided congestive heart failure may ensue when worm burden is high, and signs can include jugular distension, ascites, marked exercise intolerance and hepatomegaly.


According to numerous clinical cases of heartworm in Istrai and extreme concern of truffle dog owners and breeders, program of monitoring and education has been established. The activities among the program were based on blood examination for microfilariae as detection of antigens of females in lungs and heart. According to the results foci of highest prevalence were recognized. Foci of subcutaneous dirofilariosis were also detected.