Heartworm disease occurs when a dog is exposed to the infective larvae of the parasite Dirofilaria immitis. Dogs are infected through the bite of an infected mosquito and will almost always develop the disease unless protected from infection through the religious use of preventative medications. Currently, heartworm disease has been recorded in all 50 states and in most countries around the world. Heartworm disease can infect many different species of mammals, including humans, but domesticated dogs appear to be the definitive host. Treatment for infected dogs varies based on the age of the dog, health status and severity of infection.
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Adulticide Medications
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One of the more common methods of treatment is the administration of adulticide medications. The goal of this treatment is to kill any adult worms that reside in the cardiovascular system and allow the immune system to break them down for absorption. Melarsomine dihydrochloride, known by the trade name Immiticide, is administered as two deep intramuscular injections into the back approximately 24 hours apart. Complications from this treatment include anaphylaxis and pulmonary thromboembolus, which can both be fatal if not properly managed in a clinical setting. Veterinarians advise a one-week hospitalization and several weeks of strict cage rest for a dog undergoing adulticide treatment.
Oral Ivermectin
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Another effective method for treating heartworms is the administration of oral ivermetin. The goal of the medication is to kill any circulating juvenile heartworms and disrupt the reproductive cycle of the adults, allowing the adult worms to die naturally. This approach reduces the stress on the animal̵7;s systems and has fewer side effects, but the process takes considerably longer to administer, allowing further damage to occur to the heart and circulatory systems.
IV Arsenic
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An older method of heartworm treatment that is rarely used in practice anymore is the intravenous use of arsenic. This is also an adulticide treatment. Dosing and administration of the drug was tricky and many times resulted in the death of the patient.
After Treatment
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Dogs that have been treated for heartworm disease will undergo a series of antigen tests to confirm the success of the treatment. They will follow a regimen of oral ivermectin dosing, used to eliminate circulating immature worms, thus preventing re-infection. Most dogs that have been infected with heartworms will be predisposed to developing heart and circulatory related conditions in the future due to the damage the worms cause to the internal structures of both the heart and blood vessels.
Prevention
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Prevention is the key to keeping your dog healthy. A year-round, once-a-month regimen of oral heartworm preventative medications such as Interceptor or Heartgard will prevent the dog from becoming infected by heartworm disease. This protocol has a 99.6% efficacy rate when followed per veterinary instructions.
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