Feline heartworm infection can occur in indoor and outdoor cats of any age. Although the infection can clear up on its own in some cats, it can be potentially fatal in others, especially elderly cats and kittens. Feline heartworm infection usually affects the lungs instead of the heart.
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Cause
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Mosquitoes that carry a parasite called Dirofilaria immitis transmit parasitic larvae through their bites. Cats, unlike dogs, are not natural heartworm hosts. The immune system responds to infection and prevents many worms from completing full life cycles. The worms tend to be smaller and fewer in number than those found in dogs and very few, if any, reach the heart. However, the presence of even one worm can be life-threatening in some cases due to a cat's smaller blood vessels and heart, according to the Mar Vista Animal Medical Center.
Symptoms
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Clinical signs that can begin to appear between 75 to 90 days after infection include weight loss, lethargy, coughing, panting, appetite loss, vomiting and gagging. Breathing problems in the first stage of infection are known as Heartworm Associated Respiratory Disease. Symptoms that can occur suddenly when the disease is affecting the organs include convulsions, collapse, diarrhea, blindness, rapid heart rate, breathing difficulties, fainting and sudden death.
Diagnosis
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Diagnostic procedures for feline heartworm infection include a physical exam, X-rays of the pulmonary arteries and heart, complete blood count and a heart ultrasound called an echocardiogram. Testing for heartworm larvae, or microfilaria, can also be done, but is not as reliable as other tests. Antigen and antibody testing can be used together for a more accurate diagnosis. Antigen tests can detect the presence of adult female heartworms that are at least seven months old. A positive antibody test could indicate that the immune system is responding to a current infection, but antibody levels could also be elevated from a past infection.
Treatment
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No products have been approved to treat feline heartworm infection. Cats with no symptoms can sometimes fight and recover from heartworm infection on their own. The American Heartworm Society recommends monitoring cases involving the lungs and blood vessels with chest X-rays every six to 12 months. Cortisone-type medications, such as prednisone, can be used to treat lung disease. Medications for vomiting and coughing could also be prescribed. Additional treatment, such as oxygen therapy, antibiotics or intravenous fluids, might be required in severe infections.
Prevention
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Preventives that effectively guard against feline heartworm infection include oral medications such as Ivermectin and topical medications such as Selemectin. These preventives should be used on a monthly basis. Have your cat tested for heartworm infection before beginning a preventive program. Regular checkups and preventive screenings can detect an infection early, which increases the chance of a successful recovery. Keeping your cat indoors or away from mosquito-infested areas could also lower the risk of infection.
Warning
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When left unmonitored and untreated, feline heartworm infection can damage the heart, kidney, liver and pulmonary blood vessels. Serious conditions such as heart and lung failure, obstructed blood flow in the pulmonary arteries and impaired breathing can occur.
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