Feline heartworm disease is a very different clinical entity from canine heartworm disease. In cats, the arrival and death of immature heartworms in the pulmonary arteries can cause coughing and dyspnea as early as 3 months post-infection.
Adult heartworms suppress the function of pulmonary intravascular macrophages and thus reduce clinical disease in chronic feline heartworm infection. If there is anything positive regarding feline Heartworm disease, it is that approximately 80% of asymptomatic cats self-cure.(1) Median survival time for symptomatic cats is 1.5 years, or 4 years if only cats living beyond the day of presentation are considered. Atypical worm migration is more frequent than it is in dogs, and sudden death can occur with no prior clinical signs.(2)
Though it’s role is not clearly understood, the bacterial endosymbiont Wolbachia likely contributes to the inflammatory pathology of heartworm disease. Unfortunately, the diagnosis, treatment, and management of feline heartworm disease are far from simple.
Diagnosis prior to death in feline heartworm cases is hampered by low worm burdens, the frequency of all-male infections, and nonspecific radiographic lesions.
It is up to the veterinarian to determine the correct index of suspicion and choose the right combination of diagnostic tests to achieve an answer. Treatment is symptomatic because many adult therapies are risky and they do not increase survival time.
Despite the dangers of feline heartworm disease, less than 5% of cats in the United States are on preventative drug therapies.(3) It is important for veterinarians to take a proactive preventive stance because heartworm infection in cats is a multi-systemic disease that has no easy cure.
Dr. Sarah Kalivoda
Mountain View Animal Hospital & Holistic Pet Care
(1)(2) – Feline Heartworm Infection, AC, Lee – Department of Microbiology & Immunology, Cornell University, Ithaca, NY, USA.
(3) – True Companion Animal Medicine – 2010 Nov;25(4):224-30. doi: 10.1053/j.tcam.2010.09.003.