Welcome back to the Essington Road Animal Hospital blog! This month is Heartworm Awareness Month, so this week we rounded up the questions we get asked most about this crazy parasite in dogs. For our feline fans out there, we’ll be back next week with an article on cats (no dogs allowed!). We’ll post on our Facebook and Instagram pages when that article is ready to go. For now, here are answers to some questions you may have always wondered, but never had a chance to ask:

Why do you need a blood sample to test for heartworm?

Great question! Unlike the intestinal worms we can find in stool, heartworms live (and breed) in our pets’ blood vessels and heart (gross!). Blood samples are needed to find out if these unwanted guests are calling your dog’s heart home.

How do dogs get heartworm disease?

Dogs don’t have to come into contact with an infected animal to catch the parasite. It’s actually spread by mosquitos. Heartworm larvae catch a ride by being sucked up into a mosquito, then being injected into your dog when that same mosquito bites her. That means anywhere we find mosquitos (aka everywhere), can be a potential source of heartworm. If our pet isn’t on preventatives to stop them, these larvae grow into adult worms—up to 12 inches long, with as many as a couple hundred worms present at a time—and damage critical structures in the heart and lungs.

I’ve heard there isn’t heartworm disease in Joliet, or Illinois – why use preventatives here?

In 2018, 490 dogs tested positive for heartworm disease in Will and Kendall counties alone. In Illinois, the total was a staggering 5,883! In 2019, the totals are already spiking, with 70 positive tests by the middle of March in Will and Kendall counties. The rates are even higher in southern parts of the state, which means that as animals travel, the number of our dogs at risk will grow.

My pet isn’t showing any signs of illness – wouldn’t I know if he had heartworms?

This is where heartworms get their reputation as silent killers. The early stages of infestation don’t create any symptoms. Blood tests don’t even show if your pet has been infected for up to six months! While our pets are acting fine, the worms develop into mature adults, breeding more worms that clog the main blood vessels in your dog’s chest. The first symptoms aren’t shown until severe damage has been done and your dog is suffering from debilitating (potentially fatal) heart disease.

How do we find out if our dog has been exposed?

We screen all pets for exposure at least once a year, with a simple blood test. For pets who have missed a few doses of preventatives, we recommend testing before restarting, and then again six months later (since it can take up to six months for infection to show up on blood tests). This way, we can intervene as soon as possible if your dog is infected.

Why can’t we just start preventative without a test?

When pets are infested with heartworms, using preventatives can be dangerous to their health, even fatal. It’s important to find out more about what stage the infection is in and start protective medications before reintroducing preventatives. Even then, they need to be used under careful medical supervision until the infection is fully cleared.

Our dog has been on preventative year round—why are we testing her again?

Heartworms are trickier than we used to think! They are developing resistance to some heartworm preventatives. While resistance is still rare (thank goodness!), we are trying to stay a couple steps ahead of the parasite and catch resistant infections early. Plus, we’ve all known dogs who manage to spit out the occasional dose, or owners (maybe even ourselves, occasionally…) who miss a dose every once in a while. Annual screening makes sure we start fresh each year.

Have more questions about heartworm disease or your pet’s preventative plan? Give us a call or come by for a visit – we’re always happy to evaluate your dog’s lifestyle and come up with the best way to make sure he stays heartworm free.

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