Heartworms that infect dogs belong to the genus dirofilaria, which multiply inside the heart chamber and eventually impair the heart's function.
Often symptoms do not appear until months after an initial infection. The worm parasite inside the heart eventually leads to a decreased pumping activity. Affected dogs become lethargic and show less tolerance towards exercise. Later stages of the condition resemble those of valvular disease, i.e. frequent bouts of dry harsh coughing, retching, lung edema, and impaired breathing.
Heartworm infections in Northern Europe, Canada, and Alaska are rare. However, they are a common occurrence in countries where mosquitoes exist, i.e., along the Mediterranean or in the Southern United States, and many other popular holiday destinations. Transmission occurs through insects that bite animals. After being bitten by these insects, worm eggs are transmitted in the process and hatch under the skin. After hatching, emerging larvae travel by entering the blood stream to the heart, where they develop into mature worms.
A heartworm infection may be effectively treated with anthemintic (anti-helminthic) medication. If the worm load is high, complications may develop when dying worms cause anaphylactic reactions in the body. These may lead to shock and circulatory failure.
Prior to traveling to warm, mosquito populated counties, check the vaccination status of your dog. Treatment with a product that is effective against heartworms should be administered before, during, and after the vacation to areas where the risk of worm infection is high.