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Heartworm Disease Continues to Spread


Heartworm Disease is still killing dogs – and they simply don’t have to die. According to a new survey, close to half of all pet owners aren’t giving their dog a preventative. The overwhelming majority of cat owners don’t even know heartworm protection may be important for felines too.

    With Katrina region dogs that are heartworm positive, there’s fear of spreading further heartworm disease. Steve talks with experts to determine if that fear is substantiated. Also, the latest information based on a heartworm survey of vet clinics.

    Heartworm disease is an enigma. The potentially deadly disease of dogs, cats and ferrets is totally preventable. Yet, according to one recent Gallup Poll (commissioned by The American Heartworm Society and the pet pharmaceutical company Merial), only 59 per cent of pet owners offer a potentially life saving preventable to their pets.

    Statistics and numbers are often distant, impersonal and without impact. However, among the dogs rescued after Hurricane Katrina, well meaning adopters, including animal shelters and private citizens, learned first hand about the heartbreak and expense of heartworm. The majority of dogs from the region were heartworm positive; some reports indicate up to 80 per cent. Some of those animals died as a result.

    “Listen, if you live in certain places in the U.S., if you don’t protect your pet, heartworm disease is pretty much guaranteed to happen,” says Dr. Tom Nelson, president of the American Heartworm Society.

    Heartworm disease is spread by mosquitoes; the more mosquitoes there are, the more likely heartworm disease will be a problem.

    According to a 2004 Gallop Poll, among the 12,000 veterinary clinics polled, more than 250,000 cases of heartworm disease were reported. The top five heartworm states were Texas, Florida, North Carolina, Georgia and Louisiana. All 50 states had incidents of heartworm.

    Nelson says following Hurricane Floyd hitting North Carolina in 1999, 67 per cent of the dogs were found to be heartworm positive. “It think it’s unfortunate so many dogs were heartworm positive after Katrina, but I’m not surprised,” he says. Of course, the numbers were inflated by the many rescued strays who obviously were not protected with a preventative.

    Because these dogs with heartworm have been adopted all around the country, there’s been concern that incidents of heartworm may increase nationwide this Spring. Heartworm isn’t contagious from pet to pet. However, the more pets with heartworm, the more mosquitoes will pick up the disease up after they bite and continue the cycle. Heartworm disease begets more heartworm disease.

    “The question and concern is legitimate,” says Dr. Jorge Guerrero, chair of the American Heartworm Society Scientific Committee.    “But in my opinion I don’t believe enough dogs are being adopted out to truly impact endemic heartworm population in these areas. Besides, these dogs are being treated, hopefully cured and then placed on a preventative.”

    What concerns Guerrero is why so many dogs weren’t protected in the first place. Katrina area rescuers report about 40 to 60 per cent of owned dogs in the region were heartworm positive (not counting stray dogs who exceeded well over 80 per cent positive for heartworm). “Heartworm shouldn’t even exist in dogs because we can prevent it so efficiently,” says Guerrero. He points out that according to a 2001 Gallop Poll of 18,000 vet clinics, 20 per cent of dog owners simply forgot to dose their dogs with the monthly preventative.

    “Compliance remains an issue – a big one,” says Guerrero, who is an adjunct professor at the University of Pennsylvania School of Veterinary Medicine. “These products have a built in safety factor, so if you use one for a year and skip a month, there’s no problem. People are skipping several consecutive months. This is rather disconcerting.”

    There is one preventative that requires only one application every six months, an injectable given by a veterinarian, called ProHeart-6. However, responding to public concerns about safety issues, the Food and Drug Administration asked the manufacturer (Ft. Dodge Animal Health of Overland, KS) to pull it from the market to investigate further. However, nearing two years later, the FDA still has not offered a definitive scientific explanation about whether there are substantiated safety concerns concerning ProHeart-6.

    Guerrero says, “ProHeart came into the market successfully because there really was a place for it, particularly for clients who know they have difficulty remembering to offer their pet a monthly preventative, or their veterinarians know their history of questionable compliance.”

    “Lives have been lost because of ProHeart-6 not being available,” adds Nelson, who has a private practice based in Anniston, AL. “I’m disappointed with the FDA; we need a resolution (about ProHeart-6). I’d like to see the clear cut evidence from the FDA about why ProHeart should not be on the market.”

    “We need all the tools we can to fight heartworm disease,” Guerrero adds.

    However, some say the public can’t afford those tools. Dr. Zack Mills, executive director veterinary medical affairs at Merial in Duluth, GA. gets downright upset when he hears that explanation. “I don’t buy it! The cost of heartworm prevention is less than ten cents a day. I think anyone can afford that. If you can afford a cell phone, afford to buy cigarettes, you can afford to protect your pet. If you feel you can’t, perhaps you have to re-evaluate if you’re doing right for your pet. To me owning a pet is a privilege. And it’s a privilege you have to take some responsibility for.”

    It’s not only dogs who are susceptible to heartworm, cats are too. “Now, there’s a case of an even more misunderstood disease (feline heartworm),” says Guerrero. Fewer than five per cent of cats are protected with a monthly preventative.

    In dogs, treatment is expensive once heartworm is diagnosed. To date, in cats, there is no effective treatment.

    “And because many of the products (preventables) also control gastro intestinal parasites which people can get, this is also extremely important for public health, a benefit to the human population,” Guerrero says.

    “Few people understand their cats can get heartworm,” says Guerrero. “I think in cats and dogs we need to do a better job reaching out to the public with the message that heartworm is absolutely preventable.”

    Learn more at the American Heartworm Society website, which includes scientific information and even a page for kids:

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Steve Dale is a certified animal behavior specialist who has been a trusted voice in the world of pet health for over 20 years. You have likely heard him on the radio, read him in print and online, and seen him speaking at events all over the world. His contributions to advancing pet wellness have earned him many an award and recognition around the globe.

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