Cat with Yorkshire Heartworm is a potentially devastating disease that can occur in both dogs and cats. It can also be difficult to diagnose until it's in advanced stages, which means screening and prevention is vital to protecting your pets from heartworm.


Heartworm is caused by the parasite dirofilaria immitus, and it's carried from host to host by infected mosquitoes - heartworm cannot be transmitted through direct contact. When an infected mosquito bites your pet and injects the heartworm larvae, the larvae travels through the bloodstream to lodge itself in the heart and blood vessels. As it grows into an adult, it impedes the blood flow. Even though heartworms can grow to be 6-14" long, the symptoms aren't noticed until months to years after the initial infection. Dogs may have a soft cough, difficulty breathing, weakness, fainting or weight loss. Cats may also experience vomiting or gagging. If not treated, the animal usually dies of heart failure.

Heartworm Treatment

Treating heartworm consists of multiple injections to kill the adult heartworms, and antibiotics to prevent secondary pneumonia. The animal must be closely monitored with restricted activity for six weeks after treatment while the dog removes the dying heartworms from the blood stream. Restricted activity is to prevent the dying worms from breaking off pieces that plug in the lungs. Heartworm treatment is tricky depending on the level of infestation; it may be difficult to prevent more harm than good. Currently there is no approved treatment for heartworm in cats, so only the symptoms can be treated.

Prevention and Protection

Treatment is expensive and difficult so prevention is key to managing heartworms. There are a variety of safe monthly preventatives available with a veterinarian's prescription, including Heartgard® or Revolution®. Before treatment is started, your pet should be blood tested to be sure he is free of existing heartworm.

Your pet’s monthly heartworm prevention is important in keeping them healthy!

The materials, information and answers provided through this website are not intended to replace the medical advice or services of a qualified veterinarian or other pet health care professional. Consult your own veterinarian for answers to specific medical questions, including diagnosis, treatment, therapy or medical attention.

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