Heartworm disease is a serious problem that affects dogs in all 50 states. The disease is caused by parasitic worms that feed on blood and live in the arteries between the hearts and lungs of infected dogs. These worms mate and produce offspring, called microfilariae, that circulate in each infected dog’s bloodstream. The worms can cause disease and death and are expensive and difficult to treat. As a dog owner, it is important for you to know the facts about this devastating problem so that you can protect your pet.
How Do Dogs Contract Heartworm Disease?
Mosquitoes bite infected dogs and ingest microfilariae. These microfilariae develop over the course of approximately 14 days in the mosquitoes’ guts until they become infective larvae. When a mosquito with infective larvae in its gut bites your dog, your pet is infected with heartworms. The larvae develop under the skin for a few days and then enter your dog’s tissues where they undergo further development and migrate to the pulmonary arteries. Once inside these arteries, the worms develop into adults. These adult worms breed and start the cycle again. The development from larvae to sexually mature adults takes seven to nine months.
What Are the Signs of Heartworm Disease in Dogs?
In the early stages of heartworm infection, there are no signs. Even dogs with adult worms in their pulmonary arteries may not have obvious signs of disease. In some cases, the first sign of heartworm disease is sudden death. When present, signs of heartworm disease can include:
- Coughing up blood.
- Exercise intolerance.
If your dog has any of these signs, you should see a veterinarian immediately, as they are all signs of serious disease.
How Do You Know if Your Dog Has Heartworms?
The only way to know if your dog has adult heartworms is to test for them. The most common heartworm test is performed in your veterinarian’s office and requires only a few drops of blood. It tests for a protein that adult female heartworms release into your dog’s bloodstream. Because the test is specific for adult females, dogs in the early stages of heartworm infection will test negative. It may take six to nine months after infection to obtain a positive test result.
Is There a Treatment for Heartworm Disease?
Currently, typical treatment for heartworm disease involves first using Ivermectin to clear microfilariae from the dog’s blood and doxycycline to target bacteria that live inside the cells of heartworms. Dogs with symptoms of heartworm disease may also be given prednisone to ease inflammation and reduce these symptoms. Two months after beginning therapy, the first of three monthly doses of Immiticide, an arsenic containing drug, is given to begin killing adult worms
Killing adult heartworms is not without risks. It can lead to fatal blood clots especially in very active dogs. For this reason, dogs being treated for heartworm need to be on severe exercise restriction over the entire course of treatment and for six weeks after the final Immiticide injection. Treating adult heartworms is hard on you and your dog. It is expensive, requires multiple visits to the veterinarian and interferes with your dog’s active lifestyle.
How Can You Prevent Heartworm Infection?
Fortunately, there are medications that prevent heartworm infection. These include topical products, such as Revolution, and oral medications such as Trifexis, Interceptor, Sentinel and Heartgard Plus for dogs. Before your dog starts to take one of these medications, however, it is important to perform a heartworm test. This is because of a potentially fatal allergic reaction that can occur when infected dogs receive certain heartworm medications.