Heartworms represent an increasingly recognized problem in cats. As in dogs, heartworms are transmitted by feeding mosquitoes and, once mature, end up in the right side of the heart and the large vessels of the lungs. For cats, the likelihood of heartworm infection is directly related to the number of infected dogs in the area.
While infection rates in cats (not the typical host for heartworms) are lower than in dogs, studies have shown that up 10-14% of shelter cats are infected. Because mosquitoes can transmit the disease, being an indoor-only cat does not prevent a cat from getting infected. Signs of heartworm infection in cats can vary in severity from asymptomatic to sudden death.
The heartworm larvae, which enter the cat’s bloodstream after it is bitten by an infected mosquito, eventually migrate to the heart or blood vessels of the lungs. Here the larvae cause a severe reaction, resulting in lack of oxygen exchange and cough.
Signs of infection are variable but most often are related to the respiratory system. A veterinarian may suspect that a cat has been infected in cases of coughing, wheezing, difficulty breathing, vomiting, lethargy or weight loss. While some cats will have very mild signs, others can develop signs of congestive heart failure. Some cats will suffer from sudden death as a result of the death of one or more worms.
Because the number of worms infecting cats is usually lower than in dogs, the diagnosis of heartworm can be more challenging. Bloodwork, x-rays and a sonogram of the heart may all be needed to determine whether or not your cat has been infected with heartworms.
Heartworms are found in cats in all 50 states, so all cats are at risk, even those animals that live indoors. However, heartworms are preventable.
Ask your veterinarian about heartworm prevention. Preventive treatment should begin after a blood test has been conducted to determine if your cat has already been exposed or is infected.
At the present time, there are no acceptable treatments for eliminating heartworms from infected cats. Your veterinarian may treat your cat’s symptoms if it is displaying signs of disease. Because of the potential for serious or fatal consequences of infection, and lack of approved treatment, preventing heartworm is the best strategy.
Isolated cases of human infection have been reported. However, the heartworm is generally not considered a risk to human health and transmission from your cat directly to you is not possible.