How Real Is The Threat Of Heartworms?

The pet owner was surprised. Her veterinarian explained her dog had tested positive for heartworm disease, but Rusty didn’t look sick. She just couldn’t believe it. When could Rusty possibly have been exposed to heartworms?

The threat is real.

All dogs are at risk for heartworms, even if they spend most of the time indoors. Why? Because one mosquito bite is enough to transmit heartworms. “Statistics indicate that in areas where heartworm is common, a very high percentage of dogs that are not on preventive medication will develop heartworm infection,” according to Stephanie Arnold, MPH, DVM, Virbac Animal Health, Research & Development.

The numbers are growing. According to the American Heartworm Society, dogs with heartworms have been reported in all U.S. states, including Alaska and Hawaii. And the numbers are rising. Veterinarians in most states reported higher numbers of heartworm positive dogs in 2004 than they did in 2001.

How do heartworms “attack” dogs?

Certain species of mosquitoes are carriers of microscopic prelarval stages of heartworms. When an infected mosquito “bites” a dog, the miniscule larvae are released through the mosquito saliva. The larvae enter through the puncture left by a mosquito, then slowly migrate through the body to the heart and lungs, here they continue to grow and reproduce. This developmental process usually takes six to seven months.

Why are they called heartworms?

Dogs are the most common hosts for heartworms, which have also been known to infect more than 30 other animal species. In dogs that are infected, adult heartworms are usually found in the right ventricle of the heart, the pulmonary trunk, or the main pulmonary arteries. It’s rare, but they’ve also been found in the right atrium, eye, skin and central nervous system.

What do they look like?

Adult heartworms are easy to identify because they look like large pieces of long, white string. Female heartworms can grow up to 12 inches long, almost twice as large as males, which have corkscrew-like tails.

How can you tell if a dog has heartworms? Heartworm disease is complex and can result from different heartworm stages. Many dogs infected with heartworms show no signs of disease. In the early stages, gradual enlargement of the heart can lead to increased fatigue and an occasional cough. Dogs in severe stages of the disease may be constantly fatigued, have a persistent cough, and difficulty breathing. At this point, recovery may be difficult, and some dogs do not survive treatment.

How do I protect my dog?

When used according to directions, monthly heartworm preventives protect against heartworm infection in virtually all dogs, and the Companion Animal Parasite Council recommends year-round prevention. Many veterinarians prescribe heartworm preventives, such as those from Virbac Animal Healththat also defend against roundworms, hookworms and tapeworms. Before prescribing heartworm medication, a veterinarian must test a dog to see if it’s already infected.

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