Dogs and Heartworm Disease: What to know

Heartworm is a worm that lives in the heart, lungs, and blood vessels of animals infected with the disease. Dogs are natural hosts to heartworms. They can have dozens (up to several hundred) of these worms at once, growing up to a foot long. These parasites cause organ damage, including the heart, lungs, and arteries. Left untreated, heartworm is deadly. Heartworm can also affect cats, ferrets, and wild animals like coyotes or foxes. Talk with your veterinarian if you have questions about heartworm disease.

Heartworm disease is spread from animal to animal by mosquitos. Adult female heartworms bear tiny offspring that live in the affected animal’s bloodstream. When a mosquito bites the animal, it passes the disease onto the next animal it bites. It typically takes six months for these larvae to mature, begin affecting the host animal, and reproduce. Adult heartworms can live inside a host animal for up to seven years.

Prevention is critical. Because heartworms are silently transmitted, it takes time before pets exhibit symptoms. Talk with your veterinarian about putting your dog on a monthly heartworm preventative medication.  

Heartworm disease in dogs is a serious condition that can lead to severe health complications. Since the heartworm larvae take time to mature, early detection is challenging. 

Symptoms can range from fatigue and loss of appetite to coughing and weight loss. As the disease progresses, dogs can experience heart failure or a swollen abdomen due to excess fluid. In severe cases, dogs can have a blood flow blockage, causing labored breathing, light-colored gums, and dark brown or red urine. 

The best way to diagnose heartworm disease in your pet is through a blood test administered by your veterinarian. This test detects heartworm proteins in the blood. Heartworm tests are typically part of your pet’s annual wellness visit with your veterinarian.  

If your dog has contracted heartworms, it is crucial to initiate a treatment plan immediately. The treatment typically spans over a month, involving injectable medication administered by a veterinarian to eliminate adult heartworms. Additionally, your vet will prescribe a drug to eradicate the larvae.  

In regions where mosquitoes are more prevalent, animal shelters and rescues often receive numerous heartworm-positive pets. Unfortunately, some owners are unable to afford the treatment, while others have neglected preventative measures, allowing the heartworm to progress unchecked. This neglect can lead to severe health complications for the pets. 

It's important to understand that without treatment, heartworms can be fatal for pets. Immediate action is necessary to ensure their survival.