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Heartworms are more common in dogs, but the disease also affects cat health. Pet parents should take steps to prevent heartworm disease in cats because there currently isn't a cure for the disease itself, only symptoms can be managed.
Mosquitos carry and transmit heartworms from one animal to another. Infected animals carry heartworm microfilaria in their blood. When a mosquito bites an animal with heartworms, the microfilaria transfer to the mosquito.
After that, it takes between ten days and two weeks for the microfilaria to become larvae. At this stage, mosquitos can transfer the heartworm disease to other animals they bite. It takes another six months for heartworm larvae to grow into adult heartworms.
Many cats do not show symptoms at all, since they have very strong immune systems. In fact, around 80% of cats that contract heartworms beat the disease independently. If a cat does show signs of heartworm disease, the symptoms are often respiratory in nature. Any related cat health questions can be answered by a cat's veterinarian.
Instances of cat worms are commonly diagnosed with a condition called HARD – heartworm-associated respiratory disease. Other respiratory diseases cause similar symptoms, so diagnosing heartworms can be difficult. Pet parents should watch for symptoms like:
Eating less than usual
Unexplained weight loss
Severe cases of heartworms may lead to seizures, fainting, or retaining fluids.
Because cats have strong immune systems, only around 10% of heartworm larvae survive to become adult worms. Due to this, lab work may not indicate the presence of heartworm microfilaria in a cat’s blood. Additional testing options include:
Antigen testing – This test may be inconclusive in cats that do not have a large number of worms in their bodies.
Microfilaria testing – This test indicates that a cat was exposed to heartworms. However, the microfilariae may not survive to develop into a full-blown case of heartworms.
Antibody testing – A negative test result is a good indication that a cat does not have heartworms. However, a positive result may be inconclusive or indicate an infection in the past.
Most veterinarians recommend that cats get tested for heartworms once per year at their annual exam. The only way to prevent heartworms in cats is to be consistent in offering cat preventatives – whether a cat stays indoors or goes outside from time to time, too.
Studies show that around 25% of cats infected with heartworms are indoor cats, so monthly preventative measures are important. It only takes a single mosquito to infect a cat with heartworms. Mosquitos are small enough to get inside the home easily, and they can flit around unnoticed. There are currently four medications approved for use on cats:
Ivermectin – This is the active ingredient in Heartgard, a chewable tablet given once monthly. It was the first FDA-approved medication for preventing heartworms in cats.
Milbemycin Oxime – This is the active ingredient in Interceptor. There is a version of this medication for cats and another for dogs. The chewable tablet also protects cats from contracting hookworms and roundworms.
Selamectin – This is the active ingredient in Revolution, one of the newer heartworm preventatives for cats. This topical medication also protects against:
Moxidectin – This is one of the active ingredients in Advantage Multi. This topical medication utilizes Imidocloprid for flea prevention and Moxidectin for heartworm prevention. Similar to Revolution, it also protects cats from roundworms, ear mites, and hookworms.
Bravecto Plus is another medication that combines two active ingredients to protect cats from parasites. It uses Fluralaner as a cat flea and tick treatment, and Moxidectin to prevent heartworms and other parasites.
Aside from preventative medication for cats, pet parents can also take steps to reduce the chance that a mosquito has access to a cat. This may include:
Closing doors and windows so mosquitos cannot enter the home
Dumping out containers of standing water around the outside of the home
Cleaning and changing the water in a cat’s bowl at regular intervals
Installing screens on windows and doors to allow airflow without pests
Many pet parents may be tempted to use mosquito repellent products to protect pet cats. However, products that contain DEET or essential oils are not safe for cats. They may do more harm than good.
Heartworms in cats cannot be cured. A veterinarian can help a pet cat by treating symptoms of heartworms with antibiotics, steroids, and bronchodilators. Some cats may need treatment for the rest of their lives to alleviate symptoms.