Heartworm Disease in Dogs

What is it?

Canine heartworm disease is a serious and potentially fatal disease for dogs and can be found worldwide among dogs. Long white worms that live in the animal’s heart are the cause. Adult heartworms can reach a length of 6 to 14 inches and a dog can have as many as several hundred of them in his system.

What does it do?

Adult heartworms in the heart and adjacent large blood vessels cause extensive damage to many of the dog’s vital organs. The lungs are the first organs affected, and as the disease progresses, the heart becomes enlarged and does not function normally.

Where does it come from?

Mosquitoes transmit the heartworm infection. When a mosquito “bites” an infected dog, it takes up blood that may contain the parasites in microfilariae form. These incubate in the mosquito for about 2 weeks, during which they become infective larvae. Then, when the mosquito bites another dog, the infective larva is passed into the second dog, infecting it. The worm larvae will then begin a six-month migration to the heart, growing and developing along the way.

Detection

Heartworm infection may be detected by your veterinarian examining the dog’s blood for the presence of circulating microfilariae or by examining the dog’s blood for antigens that are produced by the adult worms. Chest x-rays are also helpful in making a diagnosis and can help determine the amount of damage.

Signs of heartworm disease

Noticeable signs of heartworm infection in dogs include frequent coughing, sluggishness, rapid tiring, labored breathing, collapse, or sudden death. When the infection reaches critical stage, the victim is usually weak, has difficulty breathing, and may faint. At this stage, damage to vital organs is so severe that treatment is much more difficult and the possibility of complete recovery much lower.

Treatment for infected dogs

Most dogs can be successfully treated if the disease is detected early. The adult worm is given an organic acsenical drug, given to the dog through a series of injections. A few days after treatment, the worms die. Reactions to the drug are not uncommon, and there is always some risk involved in treating a dog for heartworms.

Can it be prevented?

Preventative medication has proven to be highly successful. The most commonly used method of prevention is the monthly administration of heartworm preventative medicine. This is available in tablet and chewable form and comes in several sizes according to the weight of the dog. In areas where mosquitoes thrive all year, the medication is given monthly throughout the year. Daily preventative medications are also available. It is advisable to have dogs tested before beginning the monthly medication.