April is National Heart-worm Awareness Month. Hopefully if you have a dog or cat, they are on a heartworm preventative. Heartworm infections have been diagnosed in all 50 states. Heartworm transmission does decrease in winter months, but the risk of heartworm transmission never reaches zero.

Heartworm disease is caused by heartworms which are up to a foot-long that live in the infected pets heart, lungs, and associated blood vessels. They cause lung disease, heart failure, and damage to other organs in the body. I discussed heartworm disease in cats a few months ago, and today I will talk about the disease in dogs.

The dog is one of the natural hosts for heartworms. Heartworm disease causes lasting damage to the heart, lungs and arteries and can affect your dog’s health and quality of life even after the parasites are gone. This is why year round heart-worm prevention is by far the best course for your dog. If treatment is required, it should be done as early in the disease as possible.

The life cycle of the heart-worm involves mosquitos. The adult female heartworm that lives in an infected dog, fox, coyote, or wolf produces microfilaria which are microscopic baby heartworms that circulate in the bloodstream. When a mosquito bites and takes a blood meal from the infected animal, it picks up these baby heartworms. These baby heartworms develop into an infective larval stage over 10 to 14 days within the mosquito. When the infected mosquito bites another dog, these infected larvae are deposited onto the surface of the skin and get into your dog by crawling through the puncture wound created by the mosquito when it takes a blood meal. It takes about 6 months for the larval stage to develop into an adult heartworm. The mature heartworm can live for 5-7 years in your dog. Because the heart-worms can live so long your pet can get infected with an increasing number of worms every year if not on a heart-worm preventative.

The signs of heartworm disease can vary depending on the stage of disease. In the early stages of the disease your dog may not show any clinical signs or very few signs. The longer the infection is present the more likely that clinical signs will develop. Symptoms may start off with a mild cough that tends to persist, tiring easily with exercise or reluctant to exercise, decreased appetite, and weight loss. As the disease continues to worsen it will lead to heart failure. This can result in swelling of the abdomen due to fluid buildup from congestion of the liver. Caval syndrome develops when your dog has such a large number of heartworms that they cause a sudden blockage of blood flow within the heart leading to a life threatening situation. Clinical signs include a sudden onset of labored breathing, pale gums and a port wine or coffee colored urine. Part of the treatment requires surgical removal of the heartworms, but even with this the prognosis is poor.

Heartworms are definitely a problem in South Carolina with our warm climate and abundance of mosquitoes to transmit the disease. The American Heartworm Society recommend that your pet be tested yearly for heartworms and stay on a heartworm preventative 12 months a year. Heart-worm testing only requires a small amount of blood from your dog. The test works by detecting the presence of heartworm proteins in the blood. Puppies under 7 months of age can be started on heartworm preventative without a heart worm test. Dogs over 7 months of age that have not been on a preventative, should be tested before starting a preventative. If your dog tests negative, it still should be tested again 6 months later then annually after that.

Should your dog tests positive, the chances are good that he or she can be treated successfully. The plan would be to treat any clinical signs of disease and eliminate the adult heartworms, baby heartworms, juvenile, and larval stages while keeping side effects under control. Your dog should be treated with doxycycline for 4 weeks prior to any adulticide therapy to eliminate Wolbachia. Wolbachia is a bacteria that lives within the heartworm and worsens the infection. By clearing the Wolbachia, it can disrupt heartworm transmission and decrease the problems associated with dead heartworms. Your dog should also be treated for 2 months before starting adulticide therapy with a recommended heartworm preventative to eliminate the microfilaria and prevent susceptible larval stages from developing into adults. Your dog will stay on the preventative throughout the adulticide treatment and hopefully the rest of his or her life. The adulticide therapy will likely be divided into 3 doses. The first dose is done and then the next 2 doses are given 1 month later on consecutive days. Exercise restriction during the treatment and recovery phase is needed to minimize complications. After completion of adulticide therapy, your veterinarian will do a heartworm check 6 months later to make sure the heart-worms have been eliminated.

Preventing heartworm disease is a lot cheaper than treating heartworm disease when you consider the cost of xrays, lab tests, and medications. Don’t allow your dog to go unprotected. Talk with your veterinarian about what is the best preventative for your dog and your situation. This is certainly one disease where an ounce of prevention is worth a pound of cure.