My Pet World: Preventatives would slash the incidence of heartworm in dogs and cats

Pets can run, but they can't hide from heartworm disease, which occurs in all 50 states. Without heartworm protection, even indoor cats hiding under the bed or dogs in states where heartworm isn't especially common (like California or Nebraska) aren't safe from this potentially fatal disease.

Heartworm's increasing prevalence is complicated to trace. The fact that 1) heartworm is spread by several mosquito species and 2) mosquitoes seem to be increasing in numbers tells only a part of the story. Dr. Stephen Jones, Moncks Corner, SC-based president of the American Heartworm Society, explains that coyotes are carriers for heartworm, and their numbers are climbing in many areas.

Dogs stricken with heartworm can also serve as carriers. Animal shelters and rescue organizations increasingly re-locate dogs to facilities several states away, where adoption possibilities are greater. Alas, "these dogs aren't always tested first for heartworm. Even if they are tested, sometimes it takes several tests to rule out heartworm, and there are cost limitations (to consider)," explains Dr. Robert Stannard, a board member of the American Heartworm Society "So, heartworm is spread."

To be clear, heartworm is in not contagious from animal to animal. Mosquitoes bite an infected wild canine species (such as coyotes), infected dogs or infected raccoons and then pass the "baby larvae" to other animals, including unprotected dogs, cats or ferrets not on a heartworm preventative.

"In dogs, heartworms can be up to about a foot-long and live in the pulmonary arties and heart for over five years," Jones notes.

While heartworm disease in dogs can be treated, such care is expensive and arduous.

"Certainly, treatment is no fun," Jones says. Recent work by Jones reveals that even if the heartworm treatment appears successful, the disease can leave permanent damage in dogs.

"Because the damage is inside the dog, we don't see it. Some dogs (are) never the same again," Stannard says.

A part of the problem is that if pet owners and even veterinarians aren't seeing mosquitoes where they live, and there aren't many reports of heartworm, dog and cat owners become careless. The problem "may be human nature, but pets pay the price," Jones says.

Stannard says he's been guilty himself, as his practice is in Livermore, CA, an arid area where mosquitoes aren't a big issue. Ten years ago, he began testing cats for heartworm disease. Much to his surprise, that first year 16 cats tested positive, and a total of 39 cats since 2004. The majority that tested positive were indoor cats.

"There's no treatment for heartworm disease in cats," Stannard notes.

It was only recently discovered that heartworm disease occurs about as often in cats as in dogs. The good news is, cats are sometimes able to fight off the disease with no apparent symptoms. Some cats do suffer from heartworm-associated respiratory disease (which mimics asthma), which can be treated, but respiratory disease in cats can impact their quality of life. In still other cats, the only symptom is sudden death.

"Whether we're talking dogs or cats, there is a solution: prevention," Jones says.

According to the American Heartworm Society, 64 percent of dogs leave veterinary clinics without heartworm preventatives. This figure doesn't include dogs never taken to see a vet, so it's conceivable that over 70 percent of American's dogs never receive heartworm protection. Stannard estimates that over 90 percent of cats don't received heartworm preventatives.

Some clients are concerned about product safety.

"Really, the products are so safe," says Stannard. "Getting heartworm disease isn't safe."

Cost can be a factor, and even some veterinarians don't comprehend the significance of heartworm.

The American Heartworm Society estimates that 100,000 dogs are infected with heartworm annually. The number of cats infected is unknown. While no one knows how many dogs and cats die of heartworm, Stannard says that if 90 percent of dogs and cats were on a preventative, heartworm deaths would be rare. It's that simple.

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