Jul 05 2012

Heartworm season – Is your pet protected?

What is Heartworm?

Heartworm is an internal parasite (Dirofilaria immitis) that commonly affects dogs, and is now recognized as a problem in cats. This parasite is found in the blood. When they reach full maturity, these worms can be found to live in the right side of the heart and arteries of the lungs. Often, heartworm infection can cause serious damage to the heart and arteries, eventually leading to heart failure. In some cases, damage to the liver and kidney can occur as well.

Heartworm is spread by mosquitos, who carry a larval stage of the worm called ‘microfilariae’. Mosquitos become infected by microfilariae by ingesting the blood of an infected animal in the wild. When the mosquito bites a dog or cat, it passes the larvae into this animal’s blood stream. Once this occurs, it will take 6 months for the larvae to fully mature and can survive for 5 years in the dog. They can be 6-14inches in length, and one dog can have hundreds of worms!

What Are the Signs Your Pet Has Heartworm?

Some pets may show no signs of the disease, while others may show clinical signs such as a persistent cough, reluctance to exercise, tiring easily, reduced appetite or weight loss. Severe cases may lead to fainting or thromboembolism, which can lead to death.

How to Test For Heartworm

There are two types of tests for heartworm – one that looks for the microfilaria in the blood, and one that looks for antibodies against adult heartworms present in the heart. The antibody test is often required because the microfilaria test may show as negative even when there are adult heartworms present. This is because at least two worms – a male and female – are needed in your pet for the microfilaria to be present.


Treating for Heartworm can be more difficult and dangerous for your pet than preventing it entirely. The adult worms are killed with an injectable drug given in a series of 2 injections. A few days later, the worms begin to die, and are carried by way of the bloodstream to the lungs where they lodge in small blood vessels. They slowly decompose and are absorbed by the body over a period of several months. Lodged worms can cause serious complications for your pet if they occur in heart vessels.

We recommend testing for Heartworm every year because we know that sometimes treating our pets with medications can be tricky, and treatments can be missed or spat out by your sneaky pets. None of the routine heartworm tests are able to detect immature or early heartworm infestation.  Your dog may have had an undetectable infection at the time of his/her last heartworm test, and therefore, could have a dangerous infection. Heartworm preventives WILL prevent new infections of heartworms, BUT it CANNOT prevent the progress of pre-existing heartworm infection

We also recommend using heartworm preventatives year-round. This is because mosquitoes can survive the winter inside your home, and it only takes one bite for you pet to become infected.

Remember, 1 ounce of prevention is worth a pound of cure!

highparkadmin | Seasonal

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