Feline heartworm disease: Solving the puzzle

Feline heartworm disease: Solving the puzzle

Does that cat you suspect of having asthma really have a heartworm infection? In cats, heartworm disease manifests quite differently than in dogs and has an altered infective cycle. These researchers are seeking to create a definitive model for feline heartworm disease to improve our overall understanding.

A. Ray Dillon, DVM, MS, MBA, DACVIM

Byron L. Blagburn, MS, PhD
Heartworm (Dirofilaria immitis) infection in cats was first reported more than 85 years ago.1 However, many cat owners and some veterinarians either remain unaware or do not think that heartworms can cause serious and sometimes fatal disease in cats. Most of us are familiar with the potential consequences of heartworm infections in dogs, but we fail to recognize that heartworm infections in cats can result in demonstrably different clinical responses (Table 1).2,3


Table 1: Comparison of Canine and Feline Heartworm Infections
Although the prevalence of heartworm infection in cats has been studied, unique features of feline infections make assessing the true prevalence difficult, if not impossible. A variety of techniques—including radiography, angiography, ultrasonography, and necropsy, as well as microfilariae, antibody, and antigen detection—have been used.4 The use of these different diagnostic methods makes comparison of the various studies difficult. Moreover, because many of these tests were developed for diagnosing adult heartworms in dogs, they may not be directly applicable in cats in which immature adults cause significant disease.

The nature of available tests and features of feline heartworm infections detailed in Table 1 probably result in grossly underestimated prevalences of heartworm infection in cats. Most heartworm researchers agree that exposure of cats to heartworm-infected mosquitoes is surprisingly high and that the risk of feline heartworm infection remains a concern in many regions of the country.5,6