Heartworm protein

Canine heart filariasis is a blood parasitic disease parasitic on the heart and pulmonary arteries of dogs and cats, mainly causing respiratory distress, blood circulation disorders, anemia and other clinical manifestations in affected animals. Mosquitoes are the main vectors of the disease and can infect healthy dogs with canine heartworm larvae while sucking blood. Therefore, the disease has a clear seasonal prevalence, with the highest incidence in the summer months when mosquito activity is high. In the early stage of infection, sick dogs show symptoms such as coarse and disheveled coat, loss of appetite, lethargy, dermatitis, etc. Some sick dogs show respiratory symptoms such as coughing and difficulty in breathing. As the course of the disease continues to develop, sick dogs develop anemia, swelling of the limbs, chest and abdominal fluid, etc., which can cause acute death of dogs in severe cases.

Heartworms usually complete their life history with intermediate hosts such as Aedes albopictus or Culex pipiens. Dogs are infected by the bite of mosquitoes containing infective larvae. Female worms parasitizing the canine pulmonary artery and right ventricle directly produce freely moving microfilariae that enter the circulation. Mosquitoes inhale microfilariae while sucking blood, where they develop for 2 weeks into larvae, which then continue to develop in the salivary glands into infective larvae. When mosquitoes bite other dogs, the infective larvae take the opportunity to enter the skin and muscle tissues of the final host, and eventually reach the heart and large blood vessels through the blood circulation, developing into adults after 2-3 months.

Figure 1. Life cycle of Dirofilaria immitis
(Source: Prichard RK. 2021)

Canine heartworm (Dirofilaria immitis) examination methods can be categorized into microfilarial and adult tests. A commonly used microfilariae detection method is the blood smear test, in which a pressurized droplet specimen is made from the terminal blood of a dog for microscopic examination, and microscopic observation is made for the presence of microfilariae. Blood smears can also be taken from the center of the lesion for testing if characteristic dermatologic symptoms are exhibited. This method directly identifies the species of heartworm. Whereas, adult worm detection was carried out by collecting serum samples using a modified Kntt's assay and microtiter filtration method. In addition to testing for parasites, it is also possible to test for heartworm antigen, which is the most versatile test. Based on the seasonal occurrence of canine heartworm disease, preventive measures for the disease suggest preventive drug deworming during the high temperature season every year, as well as strengthening the daily disinfection of kennels to eliminate mosquitoes and other harmful vectors in a timely manner to reduce the risk of disease transmission.

Dirofilaria immitis protein