Heartworm Disease in Dogs - The Signs, Symptoms, Treatment and Prevention of
Canine Heartworm Disease
By J. E. Davidson
Heartworm infestation can be prevented! Ask your
veterinarian
what you should be doing to keep your dog or puppy healthy and heartworm-free.
Heartworm disease is an entirely preventable condition that can be fatal to
your pet. The dog may have no symptoms until the disease becomes severe and a
blood test indicates infestation. Hundreds of dogs die needlessly every year
from this disease. Heartworm is most prevalent in the South and in subtropical
climates but exists everywhere there are mosquitoes. You can reduce your dog’s
chance of contracting Heartworm disease with preventive medicines, avoiding
exposure to mosquitoes, and routine Heartworm testing.
 Heartworms are parasitic nematodes, one of a species of roundworms. The mosquito
is vital to the intermediate stage of the life cycle of the heart worm. Adult
worms bear live young which circulate in the host animal’s blood system. When a
mosquito bites the host, the young worms (microfilariae) are ingested. Within
the insect the microfilariae go through a series of molts to the larvae stage
then migrate to the mosquito’s mouth and are passed on to their next host
through a mosquito bite. This stage takes two to six weeks depending on the
warmth of the climate.
In the new host the larvae remain at the site of the bite for a week or two,
then move to the abdomen and chest regions where they grow into immature adults.
In three or four months they begin to enter the bloodstream and lodge in the
heart, lungs and pulmonary arteries. They will grow too up to fourteen inches
long and will live five to seven years in the dog’s body. In about seven months
the male and female Heartworms begin to mate and produce microfilariae. A dog
may have only a few Heartworms or may become severely infested.
 There are no early signs of infestation. Dogs that have heavy infestations may
show symptoms such as coughing and exhaustion when exercising, lethargy, and
loss of appetite. In more advanced cases the dog may cough up blood, faint, or
experience severe weight loss. Fluid may accumulate in the abdomen causing it to
distend. The worms will cause obstructions and blockages requiring the heart to
work harder to pump blood through the dog’s circulatory system. If untreated,
the infestation will result in liver damage, congestive heart failure and death.
Some cases may be so severe that they are beyond treatment.
When diagnosed early, Heartworm disease may be treated effectively. Blood tests
can identify the antibodies the dog body produces in response to the worms. The
treatment can be taxing on the dog’s heart, lung, and kidney function and the
dog’s health must be evaluated by a veterinarian before treatment begins. Adult
worms are usually killed with an arsenic-based compound. Immiticide is the
currently recommended brand of Heartworm medication. It is more effective and
has fewer side effects than earlier formulas and is safer for dogs in the late
stages of the disease.
After treatment the dead worms will be absorbed by the dog’s body. His exercise
must be restricted for a month or two so dead worms don’t break free and travel
to the lungs possibly causing respiratory failure and death. Several weeks later
the dog will undergo treatment to kill the microfilariae in his blood stream.
Blood tests will be taken to determine successful treatment. Once treatment has
been deemed successful, the dog should be given preventive medications.
Microfilariae can live for up to two years in the dog’s system. If they are not
picked up by a mosquito they will eventually die. Pregnant female dogs may
transmit the microfilariae to their unborn puppies. The puppies won’t develop
adult Heartworms from these worms since the mosquito plays a role in the
Heartworm life cycle but they will be carriers of the parasites.
Preventive medications will also remove most adult Heartworms from dogs but it
takes 18 months for the adult worms to die. This method is reserved for dogs
whose health may not tolerate the harsher treatment or whose owners may not be
able to afford the more expensive Immiticide.
In advanced cases with substantial heart involvement, the Heartworms may be
removed surgically.
There are a number of veterinary drugs for the prevention of Heartworm disease.
Dogs should be given preventative medication year round. Any dogs more than
seven months old should be evaluated for Heartworm disease by a veterinarian
before preventive treatment begins.
Cats may also become infested with Heartworms but often rid themselves
spontaneously of the infestation. Cats who do develop Heartworm disease may also
be treated with drugs. Humans rarely become infested. The microfilariae die
shortly after entering a human lung. Granulomas will form around the dead worms
which may show up on a X-ray resembling lung cancer, and a biopsy will rule out
the life-threatening condition.
|
