(Last of two parts)
Heartworm can kill your cat. Thus, proper diagnosis is vital.
It is important to bring your pet to the doctor for tests as soon as you see one of these symptoms:
1. Collapse
2. Coughing
3. Dyspnea
4. Vomiting
5. Convulsions
6. Diarrhea
7. Vomiting
8. Lethargy
9. Blindness
10. Anorexia
11. Tachycardia
12. Weight Loss
The following tests will be done, according to Ernest Ward in “Heartworm Disease in Cats” in the VCA website:
1. A blood sample will be tested for the presence of microfilariae. But less than 20 per cent of cats with heartworms have microfilariae in their blood, and microfilariae are present for only one to four weeks. A positive test is diagnostic but a negative test means little.
2. An eosinophil count will be measured in cats suspected of having heartworms.
“Eosinophils are a type of white blood cell that occur in increased numbers when certain parasites are present. They are elevated in the presence of heartworms, but this elevation only occurs for a few months. This test is not specific, since cats with other parasites (intestinal worms, fleas, etc.) or allergies also commonly have increased eosinophil counts. An eosinophil count is often performed with a complete blood cell count (CBC) and serum chemistries during the initial diagnostic workup.,” Ward said.
3. Radiographs (X-rays) will show the size and shape of the heart, and will allow the vet to measure the diameter of the pulmonary arteries.
“Many cats with heartworms have an increase in the size of the pulmonary arteries, or the arteries may appear blunted (suddenly come to an apparent stop) on their way to the lungs, due to worms obstructing them. However, many other cats with heartworms have no abnormal findings on their radiographs, especially early in the infection.
4. Cardiac ultrasound or echocardiography allows the examiner to directly view and assess the heart and surrounding vessels.
In some cats, the actual adult heartworms can be seen, thus, you will know what you are dealing with. But most infected cats have a low number of worms, thus these are not seen, and proper treatment is not started and given.
Can feline heartworm disease be treated?
There is no drug approved for treating heartworms in cats. One of the drugs used for treating dogs has been used in cats, but it causes significant side effects.
"To complicate things further, when the adult heartworms die during this treatment, they pass through the pulmonary arteries to the lungs where the reaction to the dead and dying worms can cause sudden death,” Ward said.
When a cat is diagnosed with heartworms, there are two main choices:
1. Treat using a drug designed for dogs.
But Ward said “this drug can have serious side effects in cats including acute pulmonary (lung) failure and death. For this reason, this approach is not recommended or use.”
2. Treat the symptoms of the disease and hope the cat will outlive the worms.
“Since heartworms live in a cat for about two to three years (as opposed to five to seven years in dogs), several months of treatment are needed. When cats are in a crisis, they are treated with oxygen and corticosteroids (cortisone) to relieve the reaction occurring in the pulmonary arteries and lungs, and, if needed, drugs to remove fluid from the lungs (diuretics). When they are stable, they are treated continuously or periodically with corticosteroids. In many cats, this treatment will reduce clinical signs and improve their quality of life. However, the threat of an acute crisis or sudden death always exists,” Ward said.
3. Surgical removal of the heartworms is now the recommended treatment for cats with severe signs of heartworm disease.
“This procedure must be performed by a specialist, often at a college of veterinary medicine. Studies have shown that up to 40% of cats may die during or after this procedure, so surgical heartworm removal is typically reserved for those cats who have severe disease and a poor prognosis without surgery,” Ward said.
How to prevent heartworms
It is strongly recommended by vets that cats be given a year-round monthly heartworm preventives in areas where mosquitoes are active all year round.
Cats in colder places should be given a monthly preventative for at least six months of the year.
Ward said there are good heartworm preventives for cats which makes it easy and safe to prevent heartworm disease in cats.
Giving heartworm preventives is very important for the following reasons
1. Diagnosing heartworm is not easy for both cats and dogs.
3. Unknown Incidence. Although heartworms are not as common in cats as they are in dogs, Ward said it is possible cases of heartworm have not been known.
“As we look more aggressively for heartworms in cats with better and better tests, we expect to find that the incidence is greater than previously thought. Studies have shown that up to 15% of all cats in certain locations, regardless of whether they are indoor and outdoor cats, have been exposed to feline heartworm disease,” Ward said.
4. Treatment is not easy either.
“There Is No Good Treatment. There is simply no good treatment for heartworm-infected cats. Effective drugs are not available, and cats that seem to be doing well may die suddenly. Treating heartworm infections in cats is risky at best, and not treating these cats is just as risky. It will take about two years for the parasitic infection to be eliminated in the cat, and serious clinical signs can suddenly appear at any time during this period,” Ward said.
5. Prevention is always better, safe and easy.
“Cats given heartworm prevention drugs have not shown signs of toxicity. There is a wide margin of safety, even in kittens as young as six weeks of age,” Ward said.
6. Indoor cats can also get heartworms Too.
“Exposure to mosquitoes is required for transmission. Cats do not have to be exposed to cats or dogs infected with heartworms. Obviously, cats that go outdoors are more likely to be exposed; however, an infected mosquito can easily get into the house and infect the cat,” Ward added.