Heartworm Disease in Cats
Heartworms are blood borne parasites called Dirofilaria immitus that live in the right side of the heart and neighbouring blood vessels of infected animals. The adult worms can grow up to 30 cm in length. Heartworm disease is much more common in dogs than it is in cats, with the infection rate in cats reported to be as low as 5-20% that of the infection rate in dogs. Infection rates in dogs will be dependent on the climate and location with current prevalence in Perth considered to be low.
How do cats become infected?
Heartworm is transmitted by bites from an infected mosquito. The larvae then take six months to grow into adults which live in the heart and neighbouring blood vessels. These adult worms then produce more larvae and the cycle continues. Cats appear to be more resistant to heartworm infection compared to dogs. Heartworm disease has been reported in cats that live exclusively indoors.
How does it affect my cat?
Many cases of heartworm disease in cats will not show any symptoms. Symptoms may present suddenly or develop gradually over time.
- Sudden onset signs can include: vomiting, diarrhoea, salivation, collapse, difficulty breathing, cough, sudden death
- Most chronic, slowly developing signs can include: lethargy, coughing, weight loss, heart failure
- Signs can mimic feline asthma
How can Heartworm be diagnosed?
Heartworm disease in cats can be much more challenging to diagnose than in dogs as the tests are not as accurate and they do not have circulating larval stages that can be observed on blood smears. Your vet will advise you which are the best tests to screen your cat for heartworm disease and this will often include a combination of blood tests and chest x-rays. Some cats may also require a cardiac ultrasound.
Treatment of heartworm positive cat
If you cat is tested positive for heartworm disease, they will be placed on a monthly heartworm preventative and may be prescribed anti-inflammatory drugs to reduce the reaction of the lung tissue towards to parasites. Unlike in dogs, it is not recommended to give cats the treatment to specifically kill the adult worms as this can cause severe and potential fatal side effects.
Prevention
Heartworm disease is one disease where prevention is better and easier than cure. If you are concerned about your cat’s risk for contracting heartworm we recommend starting your cat on a preventative medication from 3 months of age. There are many different products on the market to prevent heartworm, all of which prevent larvae developing into adults.
Monthly treatments are available for cats. They are available as a spot-on formulation that also kills some intestinal worms and fleas (“Revolution” and Advocate”). Monthly treatments should be given on the same day every month.
BE WARNED Intestinal wormers are often called “Allwormers” but do not cover your pet against heartworm. Intestinal wormers are required every 3 months whilst heartworm prevention is generally monthly or yearly.
Disclaimer: Please note that the information provided on this page does not replace the advice of your veterinarian. If you are concerned about your cat’s health in any way, we strongly recommend you seek veterinary advice.
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