Critter Buzz: Heartworm a sneaky disease dangerous to dogs during warmer months

With the warm spring weather comes our universal enemy the mosquito.

This pest is more than just an annoyance during outdoor activities — it can lead to a life-threatening illness in dogs that is entirely preventable. All dogs should be treated monthly with a heartworm preventative because infestation with this parasite can cause serious and life-threatening complications.

Give your dog a once-a-month heartworm preventative to prevent infection from the start.

The heartworm is an actual worm that can grow up to 12 inches or longer. It lives primarily in the blood vessels that carry blood to the lungs to pick up oxygen to circulate throughout the body. In severe cases, these worms can even infest the heart itself and can cause high blood pressure, difficulty breathing and eventually death caused by heart failure.

Luckily heartworms are not contagious to people and are not transmitted directly from dog to dog. Instead they are transmitted between animals by mosquitoes as a form of larva that enters the mosquito when it is feeding. The host mosquito is not capable of infecting other animals immediately, but instead incubates the larvae over several weeks.

Once infectious, the mosquito spreads the disease to other dogs through its bite. The danger of infection for pets usually begins in the spring after a few weeks of warm weather. In some parts of the country where there is no deep freeze in the winter, heartworm can be a threat all year long. Your veterinarian will test your dog annually for heartworm and may recommend that you keep your dog on preventative all year long.

Once infected, these immature worms can spend up to 5 months maturing in the dog’s body before migrating to the pulmonary arteries. When the worms are maturing, heartworm tests will be negative.

When the maturation process is complete, the larvae migrate to the pulmonary artery, where they grow into mature worms and release more immature worms into the blood stream, starting a brand new life cycle.

Signs of heartworm can include coughing, fainting and difficulty breathing. The animal may also be easily fatigued. Unfortunately, animals may have heartworm for several years before signs of the disease appear.

When signs finally do occur, the heart and pulmonary arteries are often so full of worms that treatment is very risky and can sometimes result in fatal side effects. Our shelter treats several dogs a year who have heartworms, and treatment for this disease is costly.

What can you do to prevent it? Without a doubt, the easiest way to ensure the health of your dog is to prevent infection from the start. Heartworm preventatives are a once-a-month tablet or chew that often also protects against intestinal parasites as well. Although these preventatives cannot treat heartworms once they are present, they can prevent your dog from getting them in the first place.

Be sure you test for heartworm every year and get your dog on a good preventative to keep his or her heart in great shape!

— Jennifer Stone is the medical director and staff veterinarian at the Lawrence Humane Society. She has been a shelter veterinarian for more than a decade.