There are two ways to treat heartworm disease. If the disease is severe, your pet is hospitalized and given heartworm medicine such as an injection of melarsomine (Rx) (brand name--Immiticide) to kill the adult worms. A second injection of melarsomine is given 24 hours later. This treatment is effective but harsh. Some pets develop a severe lung reaction to the dying worms, which is why they must be hospitalized for the heartworm treatment. In addition to developing an allergic reaction, some pets will be harmed as dead worms drift through the blood vessels and actually plug them. The plug prevents blood from reaching the cells and this causes cells to die. When material floats through a vessel in the lungs, we call it a pulmonary embolus. When the material stops and plugs up a blood vessel in the lungs, we call the material a pulmonary thrombus.
It can be especially dangerous to give Interceptor if your pet has a large number of heartworms because Interceptor immediately kills heartworms. It's the pet's reaction to a large number of dying heartworms that can be fatal. Heartgard provides a slower, safer kill of adult worms, but is not FDA-approved for use in heartworm-positive dogs. Revolution is approved for use in heartworm-positive dogs. Your veterinarian will decide which heartworm treatment is best for your pet.
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Video: Learn More About Preventing Heartworm Disease in Dogs and Cats
Mild Heartworm Infection
The treatment is for pets that have only a very mild heartworm infection. These pets are given heartworm medicines such as Heartgard Plus or Iverhart Plus every month for two years. Often the heartworm medication is begun at half the normal dose, and then increased. This form of treatment does not kill the adult worms, but kills the tiny offspring, the microfilaria. If all the microfilaria die, and over a couple years the adults die, your pet will then be free of heartworm disease.
Recently veterinarians are also prescribing the antibiotic Doxycycline to treat mild heartworm disease. The reason for this is because they have found Doxycycline kills a symbiotic bacteria that lives within the heartworm microfilaria.
Monthly heartworm medications prevent microfilaria from growing into adult worms. Some heartworm treatments also contain additional medications to kill intestinal worms that may potentially inhabit your pet's gut.
The American Heartworm Society recommends that pets remain on heartworm protection year round because when the medication isn't given consistently some pets are developing heartworm disease. The Society feels it is easier for most pet caretakers to remember to give a heartworm medicine every month than to give it a few months of the year.
