Heartworm disease is
caused by a parasite and can only be contracted through the bite of an infected mosquito. Therefore the disease is only spread during the spring, summer or fall months. It can be fatal if left untreated. Dogs and cats both can get heartworm disease but it is much more common in dogs.
The life cycle of the
heartworm is extensive and takes about 6 to 7 months. The cycle
starts with an infected mosquito, often carrying several heartworm larva,
transmitting the larva into the animal as it bites. The larva then travel
to the connective tissue of the animal where it develops over the next four
months. The larva then molt into an immature adult and travel to the right side
of the heart through the blood stream. There they mature into adult worms.
These adult worms then start producing microfilariae
(baby heartworms) that travel in the blood where they can be ingested by a
feeding mosquito. The microfilariae develop into the larva in the mosquito
and continue the cycle.
The adult worms in the heart can clog the
arteries of the lungs and cause an allergic reaction
. The heart's response is to enlarge, causing coughing, respiratory distress, ascites (fluid in the abdomen) and heart failure. If detected early enough, there is a treatment for heartworm disease. The treatment involves an arsenic-like product to kill the adult worms. The medication is given intramuscularly now which is safer than the previous intravenous injection. However, the treatment does not come without risks.
There is a risk of embolism, which is clogging of the arteries in the lung, and allergic reaction. Furthermore, the treatment is more expensive than the preventative.
In cats, heartworm
disease is less common but does occur. Many cats have an immunity
against heartworms so they do not get the disease. When cats do get
heartworm disease, it is often a light infection with only a few adult worms.
Even though only a few worms are in the heart, it can cause sudden death.
Signs in cats include vomiting, coughing, sneezing
signs or just lethargy.
Heartworm disease is difficult to diagnose in cats since they often have only a few worms. This can make the tests less accurate. In order to diagnose heartworm disease in cats, two different tests are usually required. Cats cannot tolerate the same treatment used for dogs; it frequently results in death. Therefore, it is recommended to give cats the oral monthly preventative during the summer and fall months to protect them.
For dogs, it
is recommended to test for heartworm disease prior to giving your dog
preventative medicine. Giving the preventative to an infected dog may
cause severe allergic reaction. Furthermore, the manufacturer of the
monthly preventative heartworm medicine guarantees their product if you have
your dog tested yearly and you give the medicine monthly according to the
recommendation of your veterinarian.
A blood sample is required to do the test. Puppies that are less than 5 months old and/or are born during the off season for mosquitoes (November - April) are not required to be tested due to the life cycle of the
Heartworm.
There are many
preventatives available ; some are given daily and others are monthly. We recommend a broad-spectrum monthly pill, such as HeartgardŽ given from May through December. They are called broad spectrum because they kill other internal parasites (roundworms, hookworms, and whipworms) that your dog may pick up through fecal ingestion, along with the larval stage of the heartworms.
Heartworm disease is a deadly
disease that is preventable. Therefore, it is important to have
your dog tested in the spring (April) for heartworm disease prior to starting preventative medicine. The testing is generally inexpensive, especially when compared to treating a heartworm positive dog. Once the test is negative, your dog can start the preventative medicine monthly (or daily) from May through December.
