Veterinary Medicine welcomes parasitology questions from veterinarians and veterinary technicians.
With the subject line: Parasitology questions
Q: Has heartworm disease in cats been identified in 50 states?
A: No one is organizing incidence data, so we don't have an answer yet. Because heartworm disease has been diagnosed in dogs in all 50 states, the same is probably true in cats.
Q: Has the incidence of heartworm disease in cats increased, or are the tests more sensitive or being done more frequently?
A: This is difficult to answer because the heartworm antigen test in cats is positive only in cats with adult female heartworm infections. Furthermore, although the antibody test may yield a positive result in currently or previously infected patients, many veterinarians don't use it.
Q: What are the latest heartworm test recommendations for cats?
A: We recommend heartworm antigen testing yearly, but in part to increase awareness of the prevalence of heartworm infection locally. Few positive results are found, but if veterinarians suspect heartworm disease in cats, an antibody test may help confirm the diagnosis. It is helpful to use the results of antigen and antibody tests together to increase your diagnostic accuracy.
Q: What are the preventive, treatment, and monitoring recommendations for an asymptomatic cat with a positive heartworm antigen test result?
A: The preventive recommendation is to give a monthly heartworm preventive year-round that is also effective against intestinal parasites. Although surgical removal may be a treatment option, it has rarely been used. Suspected or confirmed cases of heartworm infection in cats should be treated the same way: Observe closely for clinical signs, administer a monthly heartworm preventive, monitor the antigen and antibody test results and thoracic radiographic findings every year to help identify progression or regression of disease, administer corticosteroids when a flare-up of respiratory distress occurs, and severely restrict exercise. Also giving doxycycline may be useful to kill obligate Wolbachia species bacteria that many filiarial nematodes harbor.
Michael Paul, DVM, is the executive director of CAPC and a former president of the American Animal Hospital Association. He is retired from practice and lives in Anguilla, British West Indies.