Dirofilariasis (Heartworm)

What it Dirofilariasis?

Dirofilariasis, also known as heartworm, is a prasitic worm that lives in the blood system of its host. Heartworm usually occurs in dogs and cats. It is transmitted by different mosquito species. Asian tiger mosquitoes (Aedes albopictus) are known to be an important vector in Italy and probably also in other regions where both the mosquito and the parasitic worm are present. Due to its ecology, Aedes albopictus is especially involved in transmitting the parasite into the urban environment.

There are two species of these parasitic worms and they induce two different forms of the disease. One species is mostly found in the blood vessels in in and around the heart of the infected animal. This condition is called Cardiovascular Dirofilariasis. The other species is found under the skin and causes Cutaneous Dirofilariasis. In any case, an infection is difficult to treat, but there is a prophylaxis against infection that is available for dogs and cats and has to be administered regularly.

Mosquitoes can also transmit the parasite to humans. It is believed that the human immune system eliminates most parasites, but in those cases where development does occur, the worm dies much sooner than in its natural host. However, current epidemiological studies indicate that human Dirofilariasis is increasing.

What are the symptoms of Cardiovascular Dirofilariasis?

Not all infected dogs and cats show symptoms. The symptoms may take some time to develop. They typically include fatigue, coughing, anemia, vomiting, and heart failure. The disease can be fatal for the infected animal.

In humans, an infection often comes without symptoms. The parasite often ends up in the lungs, where it may induce small lesions and nodules. When present, symptoms may include coughing (sometimes with blood) and chest pain.

These symptoms are typically hard, painless nodules that can be felt under the skin. These nodules may disappear as the worm migrates to other places. Often, such an infection leads to itchy skin irritations.

The symptoms in humans are quite similar: small, hard and elastic subcutaneous nodules which gradually grow. The parasite may also end up in the conjunctiva of the eye.

Where is Dirofilaris distributed?

Dirofilariasis is found in many parts of the world, including southern Europe, the Middle East, Southeast Asia, Australia, Japan, South America, Central America, North Americ including the wormer regions of Canad, and the coastal regions of Africa.