Heartworm Disease: Why We Recommend Year Round Prevention

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“Why does my dog need heartworm prevention? Its cold outside. There aren’t any mosquitoes?”


We are frequently asked this by clients over the late fall and winter months and our answer is always “YES”!!! To understand why we recommend heartworm year round, we need to look at heartworm disease and the life cycle of the parasite.


Heartworm disease begins by an infected mosquito biting a dog and passing the microfilaria into the dog through the bite. It takes 6-7 months for the microfilaria to develop into sexually mature adults and for the dog to test positive for heartworm. Once the heartworm larvae reach the heart (after about 70-90days), they grow rapidly and will live in the heart until it dies, typically between 5-7 years. The heartworms continue to grow in size once they reach sexual maturity and the females release microfilaria into the blood stream of the dog. This is why dogs are infected with multiple worms. The mass of worms act as a blockage and make the heart work harder to pump blood to the rest of the body.


When a dog is first infested with heartworms, there are usually no outward signs of the disease. Even a heartworm test will not detect the infection. Its not until the adults are sexually mature and releasing microfilaria into the blood stream that a test will show positive. At that time, they are already causing damage to the heart. Unfortunately, heartworms damage the heart faster than the body can repair it. Due to the inflammation in the heart from the heartworms, dogs may experience shortness of breath, exercise intolerance, coughing, nose bleeds, and pneumonia. If left untreated, heartworms can multiply to the point that they completely block the flow of blood to and from the heart causing death to the animal.


Heartworm prevention works by killing the microfilaria in the blood stream before they are allowed to develop into adult worms. By using prevention all year round, it ensures that any microfilaria in the blood are destroyed. If a mosquito bites your dog in November and you don’t use the prevention for the winter months, then your dog can develop heartworm disease over the winter as there is no prevention in his/her system to kill the microfilaria.


If your dog is not current on a heartworm test, is not currently on preventatives, or you skipped the winter months, please call us today to schedule a heartworm test and purchase a heartworm preventative. We offer several different brands and can help you pick a product that is right for you and your pet!