Heartworm disease is a serious and potentially fatal disease in pets in many parts of the world. It is caused by foot-long worms (heartworms) that live in the heart, lungs, and associated blood vessels of affected pets, causing severe lung disease, heart failure and damage to other organs in the body.   

Heartworm disease in cats is vastly different from heartworm disease in dogs. The cat is an atypical host (not a natural host) for heartworms, and most worms in cats do not survive to the adult stage. Cats with adult heartworms typically have just one to three worms on average, and many cats affected by heartworms have no adult worms.     

How is heartworm disease transmitted from one pet to another?  
The mosquito plays an essential role in the heartworm life cycle. Adult female heartworms living in an infected dog, fox, coyote, or wolf produce microscopic baby worms called microfilaria that circulate in the bloodstream. When a mosquito bites and takes a blood meal from an infected animal, it picks up these baby worms. Then, when the infected mosquito bites another dog, cat, or susceptible wild animal, the infective larvae are deposited.     

What are the signs of heartworm disease in cats?  
Signs of heartworm disease in cats can be very subtle or overly dramatic. Symptoms may include coughing, asthma-like attacks, difficulty in breathing, periodic vomiting, lack of appetite, or weight loss. Occasionally an affected cat may have difficulty walking, experience fainting or seizures, or suffer from fluid accumulation in the abdomen. Unfortunately, the first sign in some cases is sudden collapse of the cat, or sudden death.    

Treatment  Unfortunately, there is no approved drug therapy for heartworm infection in cats, and the drug used to treat infections in dogs is not safe for cats. The goal is to stabilize your cat and determine a long-term management plan.    

Prevention is goal  
Both outdoor and indoor cats are at risk. It is important to give your cat monthly heartworm preventives. Preventives keep new infections from developing if an infected mosquito bites your cat.