Heartworm is a disease that is transmitted by mosquitoes. It is an issue in our area, and indoor pets are also at risk. Prevention of this condition is easy and inexpensive, especially when you compare it to the expense of trying to treat the disease, the pain it causes your pet, and often the heartbreak of losing your pet.
In cats there is no treatment, and 1-2 worms can result in death. For canines, the treatment involves using a medication that is a form of arsenic. The treatment process itself has risks and is expensive; the exact therapy process and risk is dependant upon your pet's stage of illness.
Heartworm is diagnosed by a blood test. Most hospitals use a snap test that looks for the antigen to the adult female heartworm. It takes just a small amount of blood, and results are available in about 15 minutes. If this test is positive, then a confirmation test is generally sent out to a referral laboratory, that not only confirms the positive test; but also runs another test (difil) looking for an early stage of the Heartworm parasite called a microfilaria. Other tests such as a full blood panel, chest x-rays, and ultrasound are also recommended. The more widespread or advanced the disease stage, the more damage that has been done to tissue, and the higher the risk for your canine both in survival and complications secondary to treatment.
In addition to testing, your pet will be started on Doxycyline for four weeks prior to treatment. This helps to kill a parasite associated with the Heartworm that aids in the kill of these parasites and helps to make them less damaging. Your canine will also be placed on the monthly preventative to help kill earlier stages. Even if he or she tests negative for microfilaria, the adult worms present can be reproducing.
Melarsomine is the only drug approved for heartworm treatment. It is currently in limited supply, and is special ordered from Europe. It is given in a 3-dose protocol. This is started 60 days after Doxycyline treatment is started. With one dose give, a month of rest, and the next 2 doses one day after the other. Your canine will be hospitalized when this drug is given, and then must be strictly confined for a month following each treatment. As this drug kills the adult worms, the carcasses can act as clots in the bloodstream. Limited activity helps to prevent a thrombus from forming. Other medications may also be given such as Prednisone or Nsaids to control pain and inflammation.
At 4 months post Doxycyline a microfilaria test should be run again. An adult antigen test is run 6 months after adulticide therapy. In advanced cases, adult worms can surgically be removed from the heart and other tissue. This in itself poses several inherent risks.
Treatment as mentioned above is challenging, especially keeping a pet confined for 2 months. It is also very expensive. For a large dog it can be $2000 and up. Keep in mind that Heartworm screening should be done yearly, and costs about $30. Prevention costs vary depending on what product is used. HartGard for a dog under 25 lbs is about $30 for a 6 month supply. Please see the heartworm society website for more information. www.heartwormsociety.org