Pet Parasite Gets to the Heart of the Hurricanes Animal Refugees

The fresh start of animals, who were adopted and dispersed around the country courtesy of Hurricanes Katrina and Rita, may inadvertently cause heartache for their new pet owners. An estimated 60 percent of the pets displaced by Hurricane Katrina are likely infested with heartworm, a potentially fatal, mosquito-borne illness.

In response, a protocol was developed by Dr. Kate Hurley,Director of Shelter Medicine, University of California, U.C. Davis inconjunction with Dr. Tom Nelson, president of the American Heartworm Society and Professor Dwight Bowman, PhD, Professor of Parasitology,Cornell University. It recommends treating heartworm-positive animals with the standard heartworm preventative medication immediately after they’ve been diagnosed. This won’t have an effect on the underlyingdisease, but it will kill heartworm larvae in the animal’s bloodstream and thus limit the spread of the disease by making the animalnon-infectious to mosquitoes. The information is available on the AHS Web site,

Traditionally, the vast majority of heartworm cases throughout the country have been found in the wet and temperate climates of the Mississippi River Valley and the southeastern United States. Butbecause of the Katrina refugees, some veterinarians now worry thisinsidious killer could begin making inroads in low-incidence areas likethe Pacific Northwest, California and the Southwest.

Dr. Nelson says it’s too early to tell whether displacedKatrina dogs will spawn significant heartworm outbreaks in otherregions. Animals can not be accurately diagnosed with heartworm for at least six and a half months after infection, he says. In addition, the chances of transmission are dependent upon the climate of the area and time of year. Admittedly, regions that are not conducive to largemosquito populations are less likely to see heartworm outbreaks.

Dr. Dwight Bowman, a professor of parasitology at Cornell University in Ithaca, N.Y. and one of the experts who helped draft the Heartworm Society’s treatment guidelines, says a silver lining from the Katrina crisis has been increased awareness about the dangers of heartworm.

“What this event has shown us is we need to get a lot more dog son preventative medication,” Bowman says. “This disease is 100 percentpreventable using products currently available. So, there is absolutely no reason for a dog to have foot-long worms in its lungs.”

Even if Katrina dogs haven’t come to your area, Nelson says pet owners should play it safe and have their animals tested for the disease. Simple oral or topical preventive treatments, administeredonce a month, can eliminate the risk in animals that do not testpositive. The treatments also have the added benefit of pre-preventing and treating intestinal parasites, which can potentially be transmitted to people, Nelson says. The costs are low – usually between $3 and $7per month for dogs.

In contrast, the expense of treating the disease once it has taken root can sometimes run into the thousands of dollars, depending on the severity. Additionally, the treatment process – a series of injections with an arsenic-based drug called Immiticide – is protracted, often painful and sometimes risky for the animal.

Yet, the alternative is worse. Left untreated, heartworm candramatically reduce the animal’s lifespan. Nelson, a practicing veterinarian in Anniston, Ala., has seen dogs as young as two-years-old die from heartworm.

And it’s not just canine hurricane refugees that are at risk for heartworm. Research has shown heartworm is present in about 10 percent of cats. That’s a higher prevalence than feline AIDS and felineleukemia, and the rate is likely even greater with animals from theGulf. As a result, cats coming in from the hurricane zones also should be tested, Nelson says.

What exactly is heartworm? Tiny roundworms are introduced intothe bloodstream by infected mosquitoes. They embed themselves in theanimal’s heart and in the blood vessels of the lungs, where they growin size and produce offspring called microfilaria. As the worm population increases, the heart must work harder to pump blood.Eventually, the animal will exhibit the symptoms of congestive heartfailure, including lethargy, difficulty breathing and coughing.

The disaster has also shown many pets simply do not receive basic veterinary care, Bowman says.

“We’ve got to figure out how to increase that number. I thinkthe shelter medicine community in this country has done a great servicebecause they’ve made people aware of the problem, and that’s the firststep in addressing it.”

The American Heartworm Society’s guidelines for treating heartworm can be viewed at


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