Heartworm Season is Upon us....

Canine heartworm disease is a common condition in many regions of the world. It is caused by the filarial (threadlike) worm Dirofilaria immitis that lives in the pulmonary arteries (blood vessels leading from the heart to the lungs) in most infected dogs. The name "heartworm" is a bit misleading because only in very heavy infections do the worms actually reside in the heart itself.

Nonetheless, the presence of these worms causes strain to the heart and an intense reaction in the blood vessels, resulting in problems for the pooch as heartworm microfilaria (tiny larve)  is injected into the dog by infected mosquitoes.

The most important predisposing factor is failure to receive heartworm preventative medication. All dogs living in an area where heartworm disease exists are at risk, even if they live entirely indoors.

Transmission occurs when a mosquito bites an infected dog and ingests heartworm larvae (baby heartworms), which live in the bloodstream. When the insect bites another dog or cat, some of the larvae are injected under the skin. The larvae grow for 3 to 4 months and eventually make their way into the heart where they develop into adults, and the process is ready to repeat itself.

What To Watch For

Symptoms don't usually develop until damage has already occurred to the heart. Dogs can have a wide range of symptoms, with some dogs being completely asymptomatic (no symptoms at all). Symptoms usually occur because of heart failure. These include:

Coughing

Coughing up of blood (hemoptysis)

Heavy breathing

Unwillingness to exercise

Signs of right sided congestive heart failure, which include fluid distention of the belly, pulsation of the jugular veins in the neck when the dog is sitting or standing and heavy breathing.

Diagnosis
Here at AVH we use heartworm serology. This test checks for proteins in the bloodstream of the dog that are produced by the heartworms. These tests are very sensitive and accurate.

PreventionThe modern heartworm preventative medications are highly effective and, if religiously administered, should prevent heartworm infection. Look in our spring newsletter or call our office if you are unsure if you should test this year or next. All preventative medicine should be started June 1, 2011. Heartworm testing begins April 1st 2011.