According to the American Heartworm Society, heartworm disease is on the rise in our area. Updates in reported cases are made every three years. For example, in our area of Arkansas (Garland and immediate surrounding counties), in 2013, there were 26-50 cases reported per veterinary clinic. In 2016, that number had increased to 51-99 cases per clinic. In 2019, we were up to over 100 cases per clinic. Arkansas ranks fourth in the nation regarding the number of heartworm positive dogs in our state. It is a problem that veterinarians cannot ignore.
Making this more personal to us, I looked at the numbers for our clinic. Based on a random case review, within the past 12 months, we tested approximately 944 dogs. Of those, 45 dogs tested positive. This means that 4.8% of our patients tested positive for heartworms in our clinic within the past 12 months. That seems right in line with our statewide average that ranks us in the top four for this disease. Numbers for cats are not as readily available. There is testing available, but not with the ease and accuracy of testing that is available for dogs.
Heartworm disease is carried by mosquitoes, and there are at least 22 species of mosquito that are capable of carrying it. When there is a heartworm positive dog or cat in a neighborhood, all pets in the neighborhood are at an increased risk of being exposed to heartworm disease. One bite is all that is required for your pet to contract heartworms.
Once inside the body, immature heartworms travel through the tissues to the circulatory system. They stop, grow, mature, and reproduce in the blood vessel that connects the heart and lungs. The amount of damage that is done here can depend upon how many worms are present, how long they are there, and the general health of the animal that has been infected. It is a six-month process for heartworms to travel, mature, and begin reproducing. During those six months, heartworms are undetectable in the body.
Symptoms of heartworm disease are silent with immature forms of the worm, although cats can experience cough, nausea, lethargy, etc. When heartworm disease becomes symptomatic is the point at which there has been significant damage to the heart and lungs. Then, in dogs we see coughing, weight loss, difficulty breathing; basically, these are symptoms of heart failure. In cats, we might see labored breathing, blindness, seizures, or sudden death.
Treatment for dogs involves a series of medications (some oral, some injectable). Confinement during treatment is necessary. At our clinic, we follow the treatment protocol recommended by the American Heartworm Society, as this has been the most effective and safest protocol for curing dogs of heartworm disease. For cats, there is no treatment option currently available. We can treat symptoms of heart disease and lung disease, but we cannot give a treatment that will safely kill the adult heartworms in cats.
The best medicine, of course, is to prevent heartworm disease altogether. The newest forms of heartworm preventive can be up to 100% effective. In order to attain this level of protection, the medication must be administered on time, consistently, and without stopping for the life of the pet.
So, if preventatives are so good, why do veterinarians require testing for dogs every year? Firstly, heartworm testing is part of assessing the overall health of your dog. We live in a heartworm endemic area, and to ignore the possibility of a potentially fatal disease would not be a service to your pet and your family. Secondly, there is a potential for resistance to heartworm preventatives. The longer heartworms are in existence, the "stronger" they can become to fight our best preventive medications. Thirdly, it is very rare that a mortal human can perfectly administer preventive on the exact due date, ensuring that the pet swallowed and/or absorbed the medication, and there were no errors in timing or administration for the lifetime of the pet. Finally, heartworm disease is devastating. If we can save your pet's life, save them from irreversible damage to their heart and lungs, save them from suffering, then we should.