Heartworm disease in dogs is caused by a parasite called
Dirofilaria immitis. Adult heartworms, which make their home in the
dog's pulmonary arteries, can grow to over a foot in length. As
the worms increase in number, they eventually migrate to the
heart.
What's the Heartworm Hype?
Heartworm disease is a serious and sometimes fatal disease for
dogs. Any dog living or visiting an area that has mosquitoes and
infected dogs is at risk of getting heartworm disease.
To grow to adulthood, the heartworm larvae (which are called
'microfilariae') are picked up by mosquitoes that bite a
dog already infected with heartworm. The larvae then grow inside
the mosquito until they reach a stage that can be transported to a
new canine host. Dogs infected with heartworms may not show any
signs of disease for 1 or 2 years. By then, the disease may have
already damaged the dog's heart, lungs, liver, and kidneys.
The
most common signs of heartworm infection are a dry, chronic cough;
general weakness; shortness of breath; and lack of stamina. These
signs occur because the heartworms clog the heart and blood
vessels, making the heart less efficient and reducing the blood
supply. All of the signs associated with heartworm disease will be
more noticeable after extensive exercise. In advanced cases, the
dog may have congestive heart failure, swelling in the abdomen or
legs, weight loss, and/or anemia.
Diagnosing the Disease
The most common way to
detect heartworm disease is from a blood test, which detects
antigens produced by the adult female heartworms. Your veterinarian
may also look at the blood sample under a microscope to see if any
microfilariae are present. If the results of these tests are
positive for heartworm, additional blood work, X-rays, and
echocardiograms may be in order to further determine how extensive
the infection is, the number of worms
present in your dog's body, and the amount of damage they have
done to her vital organs. These tests can also help determine
whether or not your dog will be able to tolerate the heartworm
treatment.
Treating Heartworm
The vast majority of
heartworm patients are treated successfully. Treatment consists of
both eliminating the parasites and managing the heart, vascular,
and systemic problems caused by the infection.
If the infection is not too severe, your veterinarian will likely
give your dog a special medication to kill the adult heartworms.
Your dog will then need a month's rest to rid herself of the
decomposing worms.
Following this, you will need to give your dog some medicine to
kill the microfilariae. Your pet should then be put on a
prevention program to avoid becoming re-infected.
Preventing Heartworm
The easiest way to manage heartworm disease is to prevent it. This
can be done with oral and topical medications. Discuss the
available preventatives with your veterinarian to find out which
medication is best for your dog. Many veterinarians now recommend
year-round
heartworm prevention.
THE HEARTWORM LIFE CYCLE IN DOGS
• A
mosquito ingests tiny, immature worms, called microfilariae, in a
blood meal from a heartworm-infected host animal.
• The microfilariae develop inside the mosquito, becoming
infective larvae within 2 to 3 weeks.
• The mosquito transmits the infective larvae when it bites a
new host.
• The larvae develop inside the dog's body tissues, then
enter the bloodstream and move toward the heart and blood vessels.
The larvae grow into adult worms inside the heart, where they will
live until they die (about 5 to 7 years).
• After 5 to 6 months inside the heart, female worms release
microfilariae into the blood, and the cycle starts again.
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