WHAT ARE HEARTWORMS, AND HOW DOES MY PET GET INFECTED?
Heartworms are parasites that invade a pet's circulatory system and heart. The adult heartworms produce offspring called "microfilariae," which circulate in the infected pet's blood. Microfilariae are found more commonly in dogs than cats.
A mosquito feeds on the blood of a pet that has already been infected, ingests the microfilariae, and then serves as a host while the microfilariae mature for approximately two weeks. The mosquito then transfers infective heartworm larvae into a healthy pet when it bites.
These heartworm larvae migate through the pet's tissues and circulatory system and reach the heart in five to six months, where they arrive as small worms about two inches in length. Once they are in the heart, the adult worms grow and reproduce. They may reach a length of twelve or more inches and may stay in a pet's heart for several years. In a severe infection, a dog's heart may contain up to 300 worms.
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WHAT TYPE OF PET IS MOST SUSCEPTIBLE TO HEARTWORMS?
Dogs get heartworms much more commonly than cats, although the incidence of heartworms in cats is higher than once thought. Breed, sex, and age do not affect your pet's susceptibilty to heartworms. Outdoor pets come into contact with mosquitos more frequently than indoor pets and may be at increased risk for heartworm infection. The disease is found in virtually all parts of the United States and Canada.
HOW CAN I PREVENT HEARTWORM DISEASE IN MY PET?
Highly effective preventive medications are available for dogs and cats. These medications are prescribed for pets that are not infected with heartworms or that have been sucessfully treated for heartworms in the past. Your veterinarian will test your pet for the presence of heartworms before prescribing medication. The test we use in our office also screens for two tick borne diseases as well.
We live in a known heartworm area, therefore it is very important that all dogs and cats be on heartworm prevention year round. If your pet becomes infected, these medications will prevent heartworm larvae from developing into adult heartworms. It is crucial to administer all prescribed medications as directed.
As a safeguard, we recommend the annual screening test, even for pets that are on heartworm preventive medicine.
WHAT PHYSICAL SIGNS MIGHT MY PET SHOW WHEN INFECTED WITH HEARTWORMS?
Several signs might indicate the presence of heartworms in your pet. Talk to your veterinarian right away if your pet shows the following physical signs:
*Sudden weight loss
*Difficulty breathing
*Soft, persistent cough
*Tires easily
*Listlessness or weakness
Many of these signs are most noticeable after exercise. Heartworms clog the heart and/or the main blood vessels, reducing the blood supply to or from other organs such as the lungs and the liver. Major bodily functions, including breathing, are affected.
HOW IS HEARTWORM DISEASE TREATED?
Your veterinarian will require a blood sample to determine the presence of heartworms. Additional tests may be necessary to confirm the presence of heartworms. Once the presence of heartworms have been confirmed, diagnostic tests will be required to determine whether or not your pet can tolerate heartworm treatment. These test include, but are not limited to, blood-chemistry panels, radiographs (X-rays), and electrocardiograms.
DOGS...
Your veterinarian will recommend the safest and most effective treatment protocol, which will depend on the severity of the disease and the results of diagnostic testing. Today, more than 95 percent of dogs with heartworm disease is treated successfully. Most are cured with the help of medications, and the rare case requires surgery. In any case, early detection and ongoing prevention prevent needless suffering.
If your dog's heartworm infection is not too severe, the veterinarian will administer a drug to kill the adult heartworms. Complete rest is essential for the month following treatment because pieces of the dead, decomposing heartworms circulate through the blood and into the lungs during this time. Eventually the pieces are reabsorbed into the body, but if they are dislodged during this time, your dog may suffer heart or respiratory failure.
In addition to the adult heartworms, there may also be microfilariae (heartworm offspring) in your pet's blood. Your veterinarian will recommend a treatment protocol to kill them as well. Follow-up testing will be necessary to determine the effectiveness of the treatment.
Dogs with severe heartworm disease may not tolerate the treatment to kill the adult heartworms. In this case,it may be safer to treat the resulting failure of their internal organs than to try to kill the heartworms. These dogs will likely not survive more than a few months.
CATS...
The veterinary community only recently discovered that heartworm infection is more prevalent in cats than previously thought, and no heartworm treatment medications have yet been approved for use in cats. Once heartworm infection is diagnosed, three options are available.
The first option is to allow your cat's body to handle the infection without specific treatment. This option may be the best for those cats that test positive for heartworms but have no apparent signs of heartworm disease. If the cat develops signs of heartworm disease, he will need to be re-evaluated.
The second option, which is for cats that show physical signs of heartworm infection, is to treat the signs of the heartworm disease and hope the cat outlives the heartworms, which can stay alive in the cat's body for about two years. If you and your veterinarian pursue this avenue, your cat may have to be treated with oxygen and medication to help him breathe and may need to be given drugs to remove fluid from the lungs. Continuing medical treatment is usually needed.
The third option is to treat the cat with drugs approved only for use in dogs. These drugs are known to have side effects, including respiratory failure and death, in a small percentage of cats. Your veterinarian will discuss these options with you.
***Heartworm infection and disease are preventable. Have your pet checked for heartworms annually, and keep your pet on heartworm prevention as recommended by your veterinarian.
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