Heartworms are parasites, Dirofilaria immitis, that infect cats and dogs via mosquito bites. When a mosquito bites an infected pet, it drinks in young heartworms along with the blood. The worms mature within the mosquito, which transmits them to a new host when it bites another animal. The worms will then make a home in the arteries of the lungs, and perhaps the heart, of the dog or cat.
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Heartworm History
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The American Heartworm Society says an 1847 article by T.C. Osborne in the "Western Journal of Medicine and Surgery" gives the first recorded account of finding worms in the heart and blood vessels of a dog. Feline heartworms were discovered in the 1920s, according to the society.
Diethylcarbamazine
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The first medication for heartworm, diethylcarbamazine---also known by the trade name Caricide---was developed during World War II to treat soldiers in the South Pacific, according to the Patent Storm website. The soldiers had been infected with filariasis, a disease caused by parasites related to heartworms. During the 1950s, veterinarians began using diethylcarbamazine to treat heartworm as well.
Caricide's end
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The American Cyanide Company discontinued making Caricide after veterinarians and pet owners complained that dogs with a great many worms died after treatment. Patentstorm.us says this happened only in a small percentage of dogs, usually after long infestations had left them stressed, weak and emaciated.
The Birth of Ivectin
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The creation of ivectin, a heartworm-prevention treatment, was the next big breakthrough. It began in 1975, according to Stanford University, when workers at Merck laboratories discovered one of 54 soil samples they'd received from Japan for research contained a compound, Avermectin, that had antiparasitic effects. Research found the compound was naturally produced by a species of bacteria in the soil.
Testing and Beyond
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Merck began testing ivermectin in 1981, and found it was effective against filarial parasites in humans. It was approved for heartworm treatment in 1987, and is now the active ingredient in Heartguard, among other medicines.
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