Transmitted by mosquitos, heartworms in dogs can grow up to 12 inches long and have been reported in all 50 states, according to the University of Missouri Extension and the American Heartworm Society (AHS). Treatment can be hard on dogs, with painful modified-arsenic injections and danger from the disintegrated worms plugging arteries. Recently, several alternative treatments for heartworms have been accepted by the AHS and veterinarians.
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Prevention
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Because heartworm treatment can be hard on the dog and expensive for the owner, prevention is the best strategy. There are several options for preventing adult heartworms by killing them at the harmless, juvenile (microfilaria) stage. These include ivermectin (HeartGard), milbemycin oxime and moxidectin. Most preventatives are given monthly, either year round in warmer climates, or during mosquito season in cold climates.
Giving your dog a preventative does not guarantee that it will not get heartworms. Even if you remember to give the proper dose on schedule, your dog might throw it up without you noticing before it's been digested, or may have a temporary tummy upset that prevents the preventative from being absorbed. Therefore it's wise to do the simple blood test annually to check for heartworm microfilaria.
If your dog tests positive for heartworms and isn't a good candidate for the traditional immiticide treatment, you have several other options, although none are as fast acting.
Alternative Treatments
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If a dog has a mild case of heartworms, detected early and without clinical signs, it can be successfully treated by "slow-kill" methods. One involves giving monthly doses of ivermectin, moxidectin and selamectin. This can take up to two years, and because the slow die-off of the worms causes a constant load of worm segments in the bloodstream. The AHS cautions that it might not be suitable for active dogs because exertion can cause the arteries to be blocked. Additionally, a dog using a slow-kill treatment has to be monitored by a veterinarian to check for heart or lung damage.
Another slow-kill method is combining ivermectin and doxycycline. The antibiotic doxycycline kills the Wolbachia parasite, which exists symbiotically with heartworms and can increase their reproduction and growth rate. With the parasite eliminated, the heartworms become sterile and die off without reproducing. Length and schedule of this treatment is still being fine tuned since the parasite was only discovered in 2007. The AHS suggests the minimum course of treatment should be 36 weeks.
Risky Treatments
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An Internet search for alternative heartworm treatments will bring up a lot of websites selling "natural," "homeopathic" or herbal treatments. None have been proven effective in treating heartworms and may actually hasten disease process by allowing the worms to proliferate without proper treatment.
Some dog owners try to save money by purchasing liquid ivermectin (Ivomec) formulated for livestock and reducing the dose for their dog. While this can be effective, Mary Straus of the DogAware.com cautions that it can be easy to administer a toxic dose to a dog, and it's critical to dilute it properly. Some veterinarians will help in figuring out the correct dosage.
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