April is Heartworm Awareness month! We’d like to take a moment to make sure everyone understands the severity of this disease and how it can be prevented. Heartworm disease is a serious and potentially fatal condition that affects dogs and cats. This condition is caused by a parasitic worm called Dirofilaria immitis, which is transmitted through the bite of infected mosquitoes.

Prevalence of Heartworm Disease

Heartworm Disease incidence map from CAPC

According to the American Heartworm Society, heartworm disease has been diagnosed in all 50 states, and is particularly prevalent in areas with warmer climates and higher mosquito populations. In 2022, at least 4,584 dogs tested positive for heartworm disease in Missouri; 28 of tested dogs were positive here in Taney County. Cats can get sick with only 1-3 heartworms, so our current heartworm tests aren’t so great at finding these cases.

Heartworm Disease in Dogs

heartworm awareness

heartworms in an infected dog found on necropsy

Heartworm disease in dogs cause significant damage to the heart, lungs, and other organs, and can lead to severe illness, reduced quality of life, and even death.

Symptoms of heartworm disease in dogs can vary depending on the severity of the infestation. Many dogs are free of obvious signs of disease at the time of a positive screening test, but heartworm disease eventually causes signs like coughing, difficulty breathing, fatigue, and loss of appetite. In severe cases, dogs may experience heart failure or other life-threatening complications.

Heartworm Disease in Cats

In cats, we typically see respiratory signs (“heartworm associated respiratory disease”) following infestation with 1-3 adult worms or even just from immature heartworms. Feline symptoms may include coughing, asthma-like respiratory attacks, vomiting, anorexia, weight loss, difficulty walking, fainting, seizures, or sometimes even sudden death. For more information about heartworm disease in cats, please check out the American Heartworm Society.

heartworms symptomsPreventing Heartworm Disease

The good news is that heartworm disease is preventable. One of the most effective ways to prevent heartworm infection in pets is through the use of monthly heartworm preventatives, which are available in a variety of forms including pills, topical solutions, and injections. These preventatives work by killing the immature heartworm larvae before they can develop into adult worms.

Cats are less commonly infected with heartworm disease, but even exclusively indoor cats are still at risk. Unlike dogs, there is no approved treatment for heartworm disease in cats, making prevention even more important.

Heartworm Screening

In addition to preventative measures, it’s important for pet owners to have their dogs tested for heartworm disease annually. This can help ensure that any infections are caught early, when they are easier to treat.

If you live in an area where heartworm disease is prevalent, or if you plan on traveling with your pet to an area where the disease is common, consider keeping your pet indoors during peak mosquito activity.


In conclusion, heartworm disease is a serious and potentially deadly condition that can affect dogs and cats. With proper prevention and early detection, this disease can be managed and even avoided altogether. As a responsible pet owner, it’s important to work with your veterinarian to ensure that your pet is protected against heartworm disease.

For more information, check out the American Heartworm Society!

Read more Insights from Dr. Alison!

Dr. Alison Barulich

Dr. Alison Barulich

Subscribe to Dr. Alison's Insights!

Schedule Online
Skip to content