Heartworm Prevention in Dogs

Protect Their Hearts and Yours

Heartworm disease is a fatal condition in dogs that can be caused by a single bite from an infected mosquito. Heartworms can affect dogs of any age or size—puppies, adult and mature dogs, small dog breeds, German Shepherds, Great Danes, and anything in between. Rescue dogs like Bart the Dumpster Dog are at high risk for infection, since so many spend their entire lives outside, exposed to mosquitoes, before finding a forever home. Areas with higher mosquito concentrations naturally have more cases of heartworms, but there’s not a single state in the US without infections. His sister Duchess, in fact, is positive for heartworm although her treatment was successful. Heartworm prevention is incredibly important for any dog.

What Causes Heartworm Disease?

Heartworms are parasites that get their name because they live in the heart, lungs and blood vessels of infected animals. The worms typically grow to between 6 and 12 inches long and resemble thin spaghetti. The worms live between 5 and 7 years in dogs, but even once the worms die they remain in the arteries and organs, doing damage.

The number of heartworms in a dog’s body is entirely dependent on how many larvae get into its system through mosquito bites. The worms do reproduce, but the tiny microfilariae they create don’t grow into adult heartworms. Instead, they’re transferred to mosquitoes who bite the dog. After 10-14 days in the mosquito, the microfilariae mature into infective larvae that will be introduced to another dog through a bite. Those larvae grow into adult heartworms, and the cycle continues.

The Symptoms of Heartworms in Dogs

Heartworm disease is typically diagnosed as one of four different classes. Class 1 infection is discovered through a blood test when the dog has no symptoms or very mild symptoms like an infrequent cough. Class 2 infection usually shows itself as a cough and a pet that’s tired more easily than normal. Class 3 infection will show on an x-ray and involves a more frequent cough, little interest in exercise, panting and fatigue after mild activity, and other common symptoms of illness such as a dull coat, eye and skin changes and listlessness.

Class 4 is the most critical stage of heartworm disease in dogs, known as caval syndrome. In this stage of the infection, the worms can fill the heart or its arteries so much that blood cannot flow properly. Treatment is available for all classes of the disease, but the prognosis is much better when the condition is detected as early as possible.

Heartworm Treatment and the Importance of Early Detection

Fortunately for infected rescue dogs and other pets, there is treatment for heartworm disease. But the treatment can be painful and difficult, and it can also be expensive. Once heartworm disease is detected, usually through a simple blood test, a vet will typically give a series of injections deep into the dog’s back muscles to kill the worms, and a topical cream will be prescribed to kill the microfilariae in the dog’s bloodstream. The injections contain heavy levels of arsenic, so mild to severe complications can and sometimes do occur. Hospitalization, blood tests and x-rays are usually needed during this course of treatment to monitor the dog’s health and ensure the treatment is working.

The cost of treatment can range from hundreds of dollars to a thousand or more, and can go higher if complications arise. The earlier the disease is detected, the better, both for the dog’s health and the cost. For dogs with caval syndrome in which the worms are so numerous they block blood flow, emergency surgery to physically remove them is the only potentially life-saving treatment.

Heartworm Prevention Beats Any Cure

Preventing heartworms is relatively inexpensive and far less traumatic for both pets and owners than treatment. Your veterinarian will do a blood test to check for infection and then prescribe a heartworm preventative that you give your dog once a month. In puppies less than 7 months old, no blood test is typically necessary since the infection can’t be detected for 6-7 months. A blood test is usually given 6 months after the first dose, and then annually.

Before anyone can adopt a dog, rescue dogs and puppies are typically started on heartworm preventative, but it’s important to keep up the routine after taking the dogs home. A monthly dose given late is enough to leave a pet susceptible to infection. And a dog with existing heartworms that’s given a preventative can die as a result. Regular blood testing is a simple, important step in taking care of your dog’s health.

Though rates vary by the type of preventative medication and region, the average cost of heartworm prevention is $60 – $80 per year. That’s a small financial sacrifice to make to protect your pets from the pain of heartworms. And since few things are worse for a dog lover than watching a pet suffer, protecting your dog’s health from heartworms is good for your heart, too.