Heartworm in Cats: Causes, Symptoms, Treatment

Heartworms can cause serious and potentially fatal disease in cats. Read on to find out more about heartworm in cats, including how cats get heartworm, heartworm symptoms and how to protect your cat

Heartworm in cats
Heartworm in cats

What are heartworms?

Heartworms are a type of parasitic worm that primarily affect dogs, but cats can also be affected. Heartworm infections occur across mainland Australia, but they are particularly prevalent in areas where mosquitoes are more common (tropical regions).

How do cats get heartworm?

Mosquitoes transmit both heartworm in cats and heartworm in dogs. Dogs are the primary host of heartworm. Adult female heartworms living in an infested dog produce tiny juvenile worms called microfilariae. When a mosquito takes a blood meal from a dog with circulating microfilariae, some of these are taken up. After a short period of development in the mosquito, these juvenile worms can be passed to another dog (or cat) when the mosquito takes another blood meal.

Difference between heartworms in cats vs heartworms in dogs

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There are some important differences between heartworm in cats and heartworm in dogs. The dog is a natural host for heartworms. This means that heartworms can mature into adults inside dogs and the adult worms then mate and produce offspring. Cats are an atypical host for heartworms and most heartworms in cats do not survive to the adult stage. This doesn't mean that heartworms are not a problem for cats; even without becoming adults, immature heartworm can cause significant lung disease in cats.

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Symptoms of heartworm in cats

Heartworm disease in cats can be very serious. Symptoms of heartworm in cats may include:

  • Coughing
  • Difficulty breathing
  • Vomiting
  • Decreased appetite
  • Weight loss
  • Difficulty walking
  • Fainting
  • Fluid accumulation in the abdomen

Unfortunately, the first heartworm sign in some cases is sudden collapse or sudden death.

Treatment of heartworm in cats

Unfortunately, there is no approved drug to treat existing heartworm infections in cats and the prescription medication used by vets for heartworm treatment in dogs is not safe for cats. Your vet may recommend other supportive care options.

Prevention of heartworm in cats

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Heartworm disease in cats can be fatal and there are no approved drugs to treat heartworm infections in cats. For these reasons, using heartworm prevention is extremely important.

Monthly treatment with NexGard SPECTRA® for Cats prevents heartworm disease in cats, as well as providing protection against fleas, ticks, mites, lungworm and intestinal worms (including tapeworms). It provides the most complete parasite protection, all in one easy, monthly application.

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  • Can cats get heartworm?

    Yes, cats can become infected with heartworm and significant lung disease can occur in cats due to the inflammatory response to the immature worms.

  • Is heartworm in cats treatable?

    There are no medications approved to treat existing heartworm infections in cats but your vet may recommend supportive care and monitoring. As treatment options are limited, using heartworm prevention all year-round is very important.

  • How to detect heartworm in cats?

    Diagnosing heartworm in cats can be difficult because cats typically have very low numbers of adult heartworms. Diagnosis may involve xrays, ultrasound and different types of blood tests.



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