Understanding Feline Heartworm

By Michael Fleck, DVM

Heartworm Disease in the canine has been well documented and, until recently, has been seen exclusively in the domesticated dog and canine-related species. Only in recent years has there been mutation of Heartworm, allowing the disease to be transmitted to other species, primarily cats.

In all Heartworm infected pets, the mosquito is the vector that transmits the disease from one infected animal to another. 

Pathology from Heartworm infection in the dog results primarily from disruption of heart and liver function or from anaphylactic reactions. The pathology of Heartworm infection in the cat is very different from the dog. In the feline, the larvae of Heartworm migrate to the blood vessels in the lungs where it transforms to an adult worm, resulting in lung disease rather than heart disease. The damage to the lung in cats infected with feline Heartworm is so specific that pathologists describe it as Heartworm Associated Respiratory Disease or “HARD.”

Canine pet owners recognize the threat of Heartworm disease and have their dogs tested annually, followed by the administration of monthly preventative medication.  Without prevention, their pet may become infected and eventually die from the disease if untreated.  Fortunately, the current treatment for Heartworm infected dogs is very safe and effective, resulting in most treated dogs surviving and living normal lives.

As a result of Heartworm disease being a relatively new feline issue, the general cat owner may not even know that Heartworm can be transmitted to cats. What adds seriousness to feline Heartworm Disease is that once infected, unlike the canine, there is no effective or safe treatment currently available and the mortality rate for feline Heartworm Disease is very high. The American Heartworm Society and The Heartworm Symposium predict that 10% of all new Heartworm cases will be in the feline. They also have shown that 25% of Heartworm infected cats reside exclusively indoors.

To prevent transmission of Heartworm in cats, the practice of administering monthly preventative medication, similar to Heartworm preventative medication administered to the dog, is an absolute must. Currently, debate exists within the veterinary community on the need for testing before scripting preventative meds. Consulting with a veterinarian will determine the best Heartworm prevention protocol. The veterinarian will recommend the monthly Feline Heartworm preventative medication that they favor.

Since grooming salons and boarding facilities have seen an increased numbers of cats in recent years, the emergence of contagious feline Heartworm Disease provides opportunities for pet professionals to review and update their guidelines in preventing Heartworm, as well as the transmission of all contagious diseases. Since Heartworm disease is transmitted by mosquitoes, insect and pest control programs should have high priorities, especially if your business is located in warm and humid weather regions with numerous lakes and retainer ponds. These bodies of water can serve as breeding grounds for these pesky parasites.  In addition, if clients are not currently administering Heartworm preventative to their dogs and cats, you should explain to them why they should.

Feline Heartworm Disease is only one of many new and existing diseases forcing the pet professionals to keep abreast of pet health news as well as establish or update safety protocols. The emergence of Heartworm Disease in the cat has triggered an opportunity to remind pet professionals that they are a significant resource for pet health news in their community.