Heartworm disease or dirofilariasis is a such a serious with potentially fatal disease in dogs. It is caused by a worm called Dirofilaria immitis.

They can be as long a 14 inches long. Heartworms live in the heart and lung's arteries of infected dogs. They survive up to 5 years and, during this time, the female produces millions of young (microfilaria). These young live in the bloodstream, mainly in the small blood vessels.

This Clogs the arteries and interfers with the functions of the heart to pump blood.
Signs are breathing difficulty, coughing, weight loss and exercise intolerance.
It is important that your dog be tested prior to starting on the preventative medication as severe reactions can occur if the medication is given to an already infected dog. The test is very accurate and requires only that a small blood sample be taken. Heartworm can be prevented by a medication that will kill the infective larvae spread by the mosquitoes. These medications are highly effective in preventing heartworm if given properly. Prevention is most important. A dog that is already infected with heartworm disease can be treated, it is both costly and hazardous.