The adult parasites live in the heart and the pulmonary arteries, have the appearance of "threads" hence the name filariasis and reach a length of 20-25 cm. The larvae live instead in the cardiovascular system. Following the bite of infected dogs by mosquitoes, they aspire with the blood the larvae which develop within their salivary glands and become able to infest another dog. Once they enter the new host, the larvae begin their migration that lasts 6-7 months in the entire body ending with the transformation phase from larva to adult in the heart and here produce more larvae to start a new cycle.
Cardiopulmonary filariasis is initially asymptomatic. The increase in the number of parasites causes clogging of the arteries and heart chambers leading to heart failure, which can be of various degrees: mild, with no symptoms, to severe with very marked symptoms ( continuous cough and collection of fluid in the abdomen). The symptoms become evident above all in animals who practice physical effort as they manifest signs of tiredness and fatigue, while in dogs that do not exercise the disease manifests itself in 2 -3 years.
It can be considered endemic in northern Italy but is also present in some wetlands in central Italy. The disease is not incurable, however, depending on the time elapsed from the contagion to the diagnosis there may have been damage to the walls of the heart and blood vessels so the dog will remain cardiopathic for life. The therapy is carried out by means of an arsenical compound administered intramuscularly that kills the parasites. It is important that the treated animal should be at complete rest because the killing of these parasites provokes their entrance into the bloodstream, generating blood clots that could block some vessel, so it is necessary that the veterinarian determines the prognosis, that is, the necessary time for which the animal's immune system reacts by eliminating the dead parasites from the bloodstream. As a result we understand the importance of implementing adequate prophylaxis especially for those who live in or frequent the areas considered endemic.
Prophylaxis is performed by a series of substances belonging to the class of Macrolide Endectocides. These are obtained by fermentation of bacteria of the Streptomyces kind and they are active at very low concentrations. They are also active against ectoparasites, in particular nematodes and arthropods. The molecules most commonly used are: Milbemycin oxime; Ivermectin; Selamectin; Moxidectin; they exist on the market also associated with other molecules always with an antiparasitic activity. The administration of these molecules is useful as a prophylactic with the dosage of one tablet a month.
Remember that ivermectin is toxic for dogs of the Bobtail and Collie breeds. If you live or go on vacation in endemic areas further preventive mechanisms are advisable to avoid mosquito bites by using repellents made from Neem oil given as a spot-on every 20 days, or as a spray every day.