Signs of Heartworms in Dogs

Dirofilariasis, or canine heartworm disease, is a serious disease in dogs throughout all geographical areas of the United States. Adult heartworms cause damage to the canine heart and lungs by impeding their proper function. A simple blood test by your veterinarian can detect heartworms in your pet.

Adorable Scratching Puppy
"Durn mosquito bite. I'm glad I'm protected."
credit: goldyrocks/iStock/Getty Images

Heartworm Life Cycle

When a mosquito bites a dog infected with heartworms, the mosquito ingests microfilariae, or heartworm larvae. The microfilariae migrate from the mosquito's digestive tract to its abdomen. After two to three weeks of growth there, the microfilariae become infective. Once they're infective, each canine that the mosquito bites becomes infected with heartworms.

Where Heartworms Reside

After heartworms enter a dog's skin from the bite of a heartworm-larvae-infected mosquito, they grow in the skin, then enter the bloodstream through the walls of a small vein. The heartworms then travel up the vein and arrive in the right-side chambers of the canine heart. Here they mature into adults in about nine months. Male and female heartworms, approximately 8 to 16 inches in length respectively, extend though the heart valves and do not allow them to close completely. In a severe infestation, heartworms migrate up the pulmonary artery and clog the lungs' blood vessels. Male and female heartworms reproduce and exacerbate the problem.

Signs and Symptoms

There are no signs or symptoms when an infected mosquito bites your pet. As the heartworm population grows within the dog's system, though, he might develop a cough and become more sensitive to exercise, while tiring easily. Signs of an infestation include labored breathing, vomiting, coughing, listlessness and weight loss.

Veterinary Intervention

As with any changes in your pet's normal health, make an appointment with your veterinarian to have tests done and make an informed diagnosis if you four-legged buddy displays any signs that he might have heartworms. Coughing and vomiting can be signs of a quite different disease or parasite infection, but you need to check it out either way.

Proactive Approach

The best approach to preventing heartworms is to have your dog tested when you first bring him home. Your veterinarian will place him on a heartworm preventative to have a proactive, rather than reactive, approach to a healthy buddy. As long as you keep the dog current on his heartworm preventative product, the dog should never get heartworms. If you cease treatment even briefly, you'll have to have the dog retested before he can begin taking the preventative product again.