Heartworms are spread to dogs when a mosquito takes a blood meal and transmits the larvae to the dog. Larvae mature in the dog to become male and female adult worms where they reside in the heart, lungs, and associated vessels. The offspring of the adult worms are released into the blood supply. These offspring, microfilariae, are detected 6 to 7 months after the initial infection by the heartworm tests in your veterinarian's clinic.
The severity of heartworm disease is determined by the number of adult heartworms circulating in the body and the activity of the infected dog. Most dogs with heartworm infections do not show any clinical signs. Their infection is detected by annual heartworm tests by a veterinarian. Those showing clinical signs may vary from cough and exercise intolerance (mild) to collapse, fluid accumulation in the abdomen or death (most severe cases).
Once heartworms are diagnosed in a dog, your veterinarian will recommend a thorough physical exam, baseline blood work and chest x-rays to determine the overall health of the dog. These findings will help the veterinarian develop a plan for treating the infection and also help give a prognosis. The goal of heartworm treatment is to kill all adults and microfilariae. Immiticide, by Merial, is the only approved adulticide product. Your veterinarian will develop a protocol for treating with Immiticide which may include 2 or 3 injections over 48 hours or 2 months. Adverse reactions are common with Immiticide treatment including fever, cough or restlessness. In some cases, sudden death has occurred. Because of these serious side effects, it is important to work with your veterinarian to develop the best plan for your dog. Strict activity restriction is also required post-treatment, to help minimize the chances of these side effects.
Retesting for heartworms 4-6 months post treatment is required to be assured that the treatment was successful. It is also important to talk to your veterinarian to decide on the best heartworm preventative for your dog. Year round protection is strongly recommended.
For more information visit the American Heartworm Society's website at: http://www.heartwormsociety.org/pet-owner-resources/canine-heartworm.html
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