DISTRIBUTION
Heartworm disease and subcutaneous dirofilariasis are common in subtropical countries; however, they are appearing more and more frequently in Europe as well. It is mainly common in the southern part of the continent, but more and more reports are coming from countries further north. In our country, subcutaneous dirofilariasis caused by Dirofilaria repens has been known for decades. The first observation of Dirofilaria immitis in Hungary occurred in the last decade. Climate change plays a role in the increasing number of cases caused by these two Dirofilaria species.
AFFECTED HOST SPECIES
Mosquito vectors are essential to the developmental cycle of Dirofilaria species, which can infect dogs, wild carnivores, and rarely humans. Many other mammalian species are susceptible to infection, such as cats, bears, golden jackals, weasels, ferrets and rodents. Carnivores, especially dogs, can become infected with subcutaneous dirofilariasis without showing any symptoms, and rarely humans can be affected, too, with less severe symptoms. Based on national data, 563 dogs were found to have subcutaneous dirofilariasis between 2006 and 2009. Heartworm disease in dogs infected in this country was first detected in 2007. Since then, an increasing number of dogs have been diagnosed with heartworm disease caused by Dirofilaria immitis.
Transmission AND VECTORS
The infection is transmitted by mosquitoes, with nearly seventy mosquito species potentially capable of spreading it. In Hungary, Dirofilaria species have been confirmed in several species, mostly in Aedes spp., and Culex species.
SYMPTOMS
In humans, symptoms appear after 2-3 months following infection with Dirofilaria immitis. The larvae can cause lesions by reaching the lungs. Symptoms may include cough and chest pain, fever. In dogs, it can be asymptomatic for years; however, most cases are characterised by allergic reactions, fever, high blood pressure, inadequate blood supply to the right side of the heart, anaemia, dead worms can cause embolism or even sepsis, heart failure, inflammation of the liver and kidneys caused by vascular blockage. In cats, the disease mainly affects the lungs. In humans, the presence of Dirofilaria repens is often completely asymptomatic; if it does occur, the parasite causes local swelling and subcutaneous nodules. Chronic cough, shortness of breath, fatigue, weakness, loss of appetite, weight loss, fever, suppuration of the infected area, eczema, oedema may occur. In our country, 118 human cases caused by Dirofilaria repens were reported between 2001 and 2018, most of them involving subcutaneous connective tissue, eyes and less frequently lymph nodes and lungs. In pets (dogs and cats), allergies, itching and hair loss occur in the affected area.
TREATMENT, PREVENTION
The emphasis should be on prevention. Medicinal treatments can help to kill the worms, but may pose serious risks, as dead and drifting worms can cause pulmonary embolisms and instant death in dogs. In some cases, adult worms are removed surgically. There is no vaccination.