The History of Heartworm Medication
The first published account of heartworms in dogs appeared in "The Western Journal of Medicine and Surgery" in 1847. It was nearly 80 years later before the first infection in cats was described. Since that time, heartworm infection has been identified in animals across the world, with Antarctica being the only continent on which it has not been found. Today, there is a monthly preventative medication that stops dogs and cats from being harmed by the deadly parasite.
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Infection
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Heartworm infection is caused by a parasite that lives in the heart chambers and major blood vessels of your pet. It is found more often in dogs but also infects cats. Symptoms include chronic bronchitis and pneumonia. A heavy infestation can cause early death. The infection begins with a mosquito bite. It is more prevalent in hot, humid areas, such as the southern United States and similar climates.
1980s
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By the 1980s, there were two preventative medications approved by the U.S. Food and Drug Administration that stopped pets from becoming infected with heartworms. However, they were neither simple nor inexpensive. The first option was diethylcarbamazine citrate, which could be given in either liquid, tablet or chewable pill. It had to be given every day during mosquito season and for up to eight weeks after the end of the season. In some regions, it had to be given 365 days a year. The other method was treatment with caparsolate. This required the pet to be hospitalized for two days of IV injections twice a year.
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Ivermectin
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Ivermectin was the real break-through in heartworm preventative and was first approved for this use in 1987. The prevention only had to be given monthly and in very low doses it kills the heartworm larvae. Heartworm infection takes place, but it is halted each month when the preventative is given. Ivermectin is the product in today's Heartgard, Iverhart and Tri-Heart Plus. There is no adverse reaction if this medication is given to a dog that is positive for heartworms and it is often used as the first step in treatment of a heartworm infection.
Milbemycin
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Milbemycin is the medication in Interceptor and Sentinel that prevents heartworms. Milbemycin is designed to kill the heartworm larvae and suppress the female worm's ability to reproduce. Unlike Ivermectin, Milbemycin can cause problems if given to a dog that is positive for heartworm infection. Because the larvae die much faster with Milbemycin, it can create a shock to the dog's system.
Selamectin
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Selamectin is the medication in today's Revolution that creates a heartworm preventative. Selamectin is related to Ivermectin. After the monthly heartworm preventative was developed, the next step was a medication that provided broad protection against parasites in dogs and cats. Revolution is designed to protect pets against heartworms, ear mites, sarcoptic mange mites, ticks and fleas, as well as roundworms and hookworms in cats. It is safe to use in heartworm-infected animals.
Moxidectin
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Moxidectin is the medication in today's Advantage-Multi and Proheart6 preventative products. Advantage-Multi is a topical solution that is applied monthly and is available for both dogs and cats. The Advantage product can be given to heartworm-positive pets with no adverse side affects. Proheart6 is an injection and is available only for dogs. The injection, which is given every six months as a preventative, was withdrawn from the market in 2004 after several adverse reactions were reported. It returned to the market in June 2008.
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References
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