What is heartworm Disease and which species are susceptible to this infection?
Heartworm Disease is a serious condition which is potentially life threatening. The disease is caused by a blood-borne parasite called Dirofilaria immitis that inhabits the arteries of the lungs, heart and the adjacent blood vessels of infected dogs, cats and other mammalian species. The female heartworm can measure between 6 to 14 inches long and 1/8 inch wide. The male heartworm measures about one half the size of the female worm.
Any breed or sex of cats or dogs are susceptible to heartworm infection. Although heartworm disease has been reported in all 50 states, it is more frequently found along the Atlantic and Gulf Coasts from the Gulf of Mexico to New Jersey and along the Mississippi River.
Whilst heartworm disease is far more common in canines, recent studies of cats with heart disease and respiratory conditions have demonstrated an occurrence of heartworms in kitties which is much greater than has been previously thought. Even though in an article on heartworm disease written by Ernest Ward, DVM: cats are relatively resistant to heartworm infection when compared to dogs, with the infection rate in cats reported to be 5%-20% of the rate in dogs in the same location – cat owners should remain proactive in protecting their felines against this deadly disease. What make this even more important is that this recent study also revealed that approximately 1/3 of the cats infected with heartworm disease were indoor-only cats.
The American Heartworm Society strongly recommends owners get their cats tested every 12 months for heartworm and to give your cat a heartworm preventive 12 months a year.
How are cats infected with Heartworm Disease?
The life cycle of the heartworm is quite complicated. Two host animals are obligated to complete the cycle. Heartworms require the mosquito as an intermediate host and there are as many as 30 species of mosquitos acting as hosts which can transmit heartworms. The mosquitos ingest the immature heartworm larvae by feeding on either an infected cat or, more frequently, an infected dog. The immature larvae grow in the mosquito’s gut for 10 to 30 days and then enter its mouthparts.
When an infected mosquito bites a cat, the infected larvae are injected into the cat. The infected larvae mature and migrate for many months, eventually ending up in the right side of the cat’s heart and pulmonary arteries. They mature there into the adult heartworms that are ready to reproduce within about six months after they enter into the cat. At about eight months after infection, they start producing a new crop of larvae that will live in the cat’s blood for approximately one month. However, cats are, according to Dr. Ward, “resistant hosts” with fewer larvae circulating than dogs that are found.
Due to this life-cycle, In order for a cat to be infected with heartworm disease, the cat must be bitten by an infected mosquito since heartworms are not directly transmitted from one cat to another or from a cat directly to a dog.
What are the symptoms of heartworm in Cats?
According to the American Heartworm Society symptoms of Heartworm infection in cats can vary from dramatic to subtle signs. They can range from asthma-like attacks, coughing, and a lack of appetite, vomiting, or weight loss. An affected cat may experience fainting or seizures, have difficulty walking or have accumulation of abdominal fluid. Sadly, the first sign of infection in some cases can be a sudden collapse of the cat or even sudden death
Be proactive: Have your cats tested for heartworm infection. Since cats are less likely than dogs to have adult heartworms, this infection is harder to detect than it is in dogs. Screening for heartworm cats should include the use of both an antigen and antibody test since the antibody test detects exposure to heartworm larvae. Ultrasound and x-rays may be used to look for heartworm infection. It’s very important to have your cat tested before they are put on prevention and re-tested as your veterinarian recommends to document continued exposure and risk. Unfortunately at this time there is no approved treatment for heartworm infection in cats. Therefore, prevention is so important.
What if your cat tests positive for heartworm infection?
Although there is no current treatment for heartworm infections in cats (because the drugs for dogs are not safe for felines), prudent, appropriate veterinary care provided to cats with heartworm disease can often be very helpful. Stabilizing the cat’s condition and arriving at a long-term management plan will be your veterinarian’s goal. The American Heartworm Society also recommends that monthly heartworm preventatives are continued to help prevent any new infections in the event that your cat is, again, bitten by a mosquito.
For further information about heartworm disease in cats, visit the American Heartworm Society webpage.
To help celebrate heartworm awareness month, FloridaWild Veterinary Hospital is offering $5.00 off heartworm prevention medication.
Remember: indoor-only cats are also at risk of contracting heartworm disease. Just a tear in a screen is an open invitation for a hungry mosquito. Please share your thoughts and concerns about heartworm disease with a comment.
Photo Credit: Aki- Blue ticked Oriental Shorthair: by Jo Singer
By Jo Singer, MSW, CSW, LCSW, (Ret)