When the West Suburban Humane Society rescued Chip, a German Shorthaired Pointer, he had been living outside at the end of a chain. He rarely received attention and could move only as far as the chain would allow him. So when he came to live at the shelter, we were thrilled to give him the love and exercise he so desperately needed.

Heartworms are parasites that are transmitted through a mosquito bite. One bite is all it takes to cause an infestation. If left untreated, heartworms grow to 12 inches in length and work their way into the arteries of the heart, lungs, and other major organs, choking off oxygen and vital functions, killing the dog or cat. According to the American Heartworm Society, cats can be infected with heartworms, but it is rare and the worms do not typically live to adulthood.

Treatment is grueling. After a series of screenings and tests determined the extent of Chip's infestation, he was injected with a drug to kill the worms. As they died, they broke up into pieces. This is why Chip was forced to remain as still as possible. Exercise gets the blood moving, and in this case, the blood takes the worm pieces with them, increasing the chances of getting stuck in an artery and killing the animal.

So Chip stayed inside the kennel for nearly three months, only allowed to go outside for potty breaks. Not that he really felt like playing anyway -- the first heartworm treatment made him sick. He laid on his bed in the kennel curled up and shaking. It broke our hearts that nothing we did seemed to help him feel better. And to make matters worse, Chip liked eating blankets, potentially leading to choking, so he wasn't allowed to have one on his bed even during the coldest winter days.

As hard as this all was for Chip and hard for us to witness, his story does have a happy ending. As the treatments did their job, Chip started feeling like his old self again. We couldn't let him jump and run like he wanted, but it was better than seeing him tremble on his bed. And after he finished his treatments, we were able to make him available for adoption, and he hit the jackpot. His new family had actually been waiting patiently for months for him to get healthy so he could come home. And it seems that they are already enjoying each others' company; Chip and his new dad run together at least five miles per day.

Not all dogs are as lucky as Chip. It's tragic that this disease kills so many dogs each year when it is so easy to prevent. Heartworm preventive medicine comes in pill, topical, and injectable forms and only needs to be administered once per month. The American Heartworm Association recommends that owners should give the medicine even during winter months because climates vary greatly from region to region and mosquitoes are adapting to cold temperatures and infecting dogs. Case in point: Chip's heartworm was diagnosed in winter 2015.

So if you aren't doing so already, please use a monthly heartworm preventative medicine for your pet. Heartworm Prevention Month is a great time to get started.