Heartworm Prevention is Needed All Year Long

Posted by Southtowns Animal Hospital on April 2, 2018

Heartworm is a chronic, insidious, deadly disease that causes damage to the entire cardiovascular system.  Vessels are damaged very early on, before the infection is even detected in a test, and the longer those worms live in the vessels of the heart and lungs, the worse the damage becomes.

Adult heartworms can grow to be a foot long, and the damage to the heart and lungs occurs every time the heart pumps against the mass of the worms in the vessels.  To put that in perspective, a dog’s heart beats 80 to 90 times a minute, 24 hours a day, 7 days a week.  The more active a dog is, the faster the heart beats, and the more damage occurs.  Even after treatment, and the infection is cleared, the damage to the cardiovascular system can be permanent.

The cost of heartworm prevention is much less than the cost of treating the infection, and the treatment itself is dangerous.  There is a substantial risk of side effects from the medication, and there can be reactions to the dead and dying worms, including shock and strokes.

Dogs get this horrible infection from mosquitoes.  Mosquitoes drink blood, and if a mosquito bites a dog that has heartworm, they will carry microscopic larvae to the next dog they bite, passing the infection along.  Because most people associate mosquitoes with summer, there is a common misconception that there is a heartworm “season” or that it is only a disease of the summer months.

Nothing could be farther from the truth. Cold weather does not offer protection from mosquitoes.  There are 22 species of mosquito that carry heartworm in the USA and each species has different cold tolerance and is active at different times of the year.

Some species can stand the cold better than others and will come out of hibernation when the while hibernating and will be hungry and looking for a blood meal.  Many mosquitoes will lay eggs in water that freezes, and then will hatch in early spring when there is still snow on the ground.

Western New York has a reputation for long cold winters, but the daily temperatures vary considerably, often warming up enough for mosquito activity in December and January.  Even in years when winter temperatures are low enough to keep mosquitoes in hibernation, stopping prevention in the autumn still puts dogs at risk to develop adult heartworms by the time prevention is resumed in the spring.

For all these reasons, it is recommended that all dogs receive monthly heartworm prevention year-round.  An added benefit of this prevention schedule is that the medications used to prevent heartworms, also treat for common intestinal parasites of dogs.

If your dog has not been tested for heartworm, please contact the hospital.  The test only takes moments to draw, and results are usually available the next day.  Once your dog is tested, you can begin giving prevention.

If you have any questions, don’t hesitate to call the hospital and we will be happy to answer them for you.

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