By: Dr. Hilary Slaven
We know that heartworm disease is a sneaky one, with one small mosquito bringing the very small heartworm microfilaria from one infected dog to another. We owners have no idea that our dog has been infected, because it takes over 6 months for the worms to grow and signs to develop.
Inside the dog, the worms eventually look like this:
We know that mosquitoes continue to carry heartworm disease from dog-to-dog in the west central Indiana area. We know this because we see it, typically 1-2 dogs a month here in the Veedersburg clinic. We also see the distribution numbers throughout the country, shared by the American Heartworm Society.
Check out the distribution of heartworm disease throughout the USA with the link below:
A recent count of the number of heartworm-positive dogs at our Veedersburg clinic alone in 2016 was 17! This has been a consistent number since we started officially tracking these figures in 2007 (somewhere between 15-20 annually is typical, which translates to 1-2 cases per month).
Looking closely at the specific dogs that were positive, we see that some of the dogs were never on heartworm prevention products (such as monthly Heartgard chews, Interceptor tablets, or Proheart 6 injection), while others were. Of these dogs that were on protection, often we see a lapse in prevention (i.e., the owner gets busy and forgets to give Bandit his heartworm tablet this month, or maybe the pill is given only seasonally spring-fall).
There is a wide range in the ages of dogs that present with the disease. In fact, some of the heartworm-positive dogs were young (the youngest that we saw last year being one year of age).
Also, I can tell you that many of the dogs that presented are ‘house-dogs’, meaning that they spend the majority of their time inside the home. Unfortunately, mosquitoes tend to find us when we go outside, and dogs are no exception to this. Mosquitoes also tend to follow us inside the home and seek us out inside, too. All it takes is one bite.
Some dogs that present are sick, and we are testing them because we are suspicious of the disease based on signs and symptoms. I would say that anecdotally most dogs are not acting sick at all; rather, we find heartworm disease during their regular annual check-up along with vaccines.
When this test comes up positive, we know that the dog already has adult heartworms living in the vessels of the lungs and within the heart itself. It is already time to act, and there is damage being done internally whether the dog acts like it or not.