Protecting pets from heartworm

LOS ANGELES -- On an X-ray, if your dog's heart looks like it's clogged with cooked spaghetti, the diagnosis is likely to be heartworm.

Heartworm is transmitted by mosquitoes and can be prevented by a prescription pill. It's endemic to the Southeast, and veterinarians agree that pet owners in this region -- especially those along the Mississippi River -- must give their animals preventive medicine year-round or face a strong risk that their pets will contract a disease that's fatal if untreated.

But there is debate over whether heartworm prevention treatment is necessary in every part of the country, and whether prevention is necessary year-round.

Heartworm in dogs can be cured with arsenic treatments, but the treatment is expensive, long, painful to the animal and hard on the owner.

Dr. Shelly Rubin of Chicago, a retired veterinarian and past president of the American Heartworm Society, advocates treatment for every dog, every cat, everywhere, every month. The Society, founded in 1974, is sponsored by manufacturers of heartworm pills but run by veterinarians.

"We know heartworm exists in every single state, including Alaska and Hawaii," Rubin said.

On the other side of the debate, Dr. Marty Goldstein, a holistic veterinarian from South Salem, N.Y., said the treatment should be used as sparingly as possible depending on your location. He believes toxicity from preventive drugs and even some vaccines are causing immune systems to fail in animals trying to fight threats like liver disease and cancer.

Goldstein said he might see three heartworm cases a year, but he is seeing five to 10 new cases of cancer a week at his Smith Ridge Veterinary Center.

Dr. Mark D. Kittleson, a veterinarian and professor in the Department of Medicine and Epidemiology at the University of California, Davis School of Veterinary Medicine, doesn't give his dog Max a preventive because heartworm in Davis is so rare. But if Max traveled even 60 miles east to Grass Valley, Kittleson would want the dog to have the pill, Kittleson said.

Pets in areas where heartworm is endemic not only need preventive medicine, but they should also be tested annually to make sure they don't have the disease, Kittleson said. The test is done using a blood sample.

There are generic versions of heartworm medication, so it isn't as expensive as it once was, but even at discount online sites, it's $6 or $7 per dose.

Mosquitoes pick up heartworm larvae when they bite infected dogs. The mosquitoes then retransmit the larvae to other dogs. Eventually the worms get into the animal's blood vessels and lungs, where they can grow 10 to 12 inches long.

The infection takes six months to develop and during that time, there are few clinical symptoms beyond a cough, Kittleson said.

Most treatments involve arsenic-based drugs that slowly kill the worms, Kittleson said. Treatment involves three painful injections and six weeks of confinement for the pet, he said. Seventy percent to 80 percent of dogs that undergo the treatment survive, Kittleson said. Treatment can cost $1,000.

The preventive pills work for cats as well as for dogs, but the arsenic treatment is toxic to cats. Some cats work the worms out of their systems.

People rarely get heartworm. If a worm does try to develop in human lungs, it's likely to do little more than leave a scar on the lung, Kittleson said.

Because mosquitoes carry many diseases besides heartworm (West Nile virus, for example, which is harmful to humans), abatement programs are priorities in many regions. Homeowners can help by eliminating standing water and adding mosquito-eating fish to ponds.

William Foreyt, a professor of parasitology for 35 years at Washington State University, conducted a heartworm study from 2005 to 2007, looking at 556 coyote hearts from animals trapped in Central and Eastern Washington.

"None of those coyotes was infected," Foreyt said.

He does not give his dogs preventive medicine. "In my opinion, we do not have heartworm transmission," he said. "Our nights are too cool and we don't have enough warm nights to allow the parasite to develop in the mosquito for the required length of time."

On the other hand, he noted, Washington state received two shipments of Katrina animals and 50 percent of them were infected with heartworm.

But even if you live in a place where heartworm is uncommon, your dog may encounter the disease elsewhere. For that reason, Foreyt recommends pet owners give preventive medicine if they're vacationing with pets in heavy mosquito country.

Goldstein also thinks it's unnecessary for animals to take the pills year-round in the coldest parts of the country. "It has to be above 57 degrees for 10 to 14 days" for the heartworm larvae to mature in the mosquito, he said, suggesting that doses can be skipped in the coldest winter months.

In addition, he said, some products say doses provide 45 or 55 days of protection. Pet owners are often instructed to give the pills monthly so they don't forget, even if the protection period is longer than 30 days.

The preventive drugs are safe, approved by the Federal Drug Administration, and have few side effects, Rubin said. Some medications also prevent and control parasites like roundworm, tapeworm, whipworm, hookworm and fleas, he said.

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Online:

http:www.vmth.ucdavis.edu

http://www.vetmed.wsu.edu

http:www.heartwormsociety.org

http://www.ahvma.org.

http://www.drmarty.com

http://www.smithridge.com