There are a lot of misconceptions about heartworm out there. “My pet stays indoors, so she can’t get heartworm.” “Only dogs that live on farms get heartworm.” “Cats can’t get heartworm.” Unfortunately, all this misinformation is allowing well-meaning pet owners to inadvertently allow their pets to be vulnerable to the long-term effects of heartworm disease. When caught early, heartworm is very uncomfortable but treatable. When caught too late, it can lead to disastrous respiratory problems and even death. Here’s what every conscientious pet owner needs to know about heartworm right now.

Nearly 1 in 200 Dogs Will Get Heartworm Each Year

Heartworm cases reported by veterinarians in the U.S. rose by over 21% between 2013 and 2016. The American Heartworm Society says that the number of positive heartworm tests conducted by veterinarians continues to inch up every year. Why the uptick? Researchers suggest that environmental changes are allowing mosquitoes – the host for heartworm parasites – to thrive. Even a one or two-degree temperature rise can cause the mosquito population to explode in a given area, putting pets at risk of contracting heartworm.

All 50 U.S. States Have Heartworm

Because heartworm isn’t only carried by mosquitoes, it’s found in all fifty states. While the warmest states report the highest number of heartworm cases, more temperate states like California are also seeing a rise in cases, particularly around urban “hot spots.” Since heartworm parasites can live in the body for years before detection, it’s entirely possible for an infected pet to move from one state to another, carrying the parasite with him. This is one reason it’s critical to have your pet tested for heartworm every single year.

Cats Get Heartworm at 5-20% the Rate of Dogs

…but they do get it. Heartworm in cats is actually quite unique because the worms cannot usually live to adulthood with the cat as host. When they do, however, they can lead to serious respiratory issues and oftentimes death. Cats with heartworm aren’t likely to show many symptoms, and their disease can’t readily be “treated” the way it can be in dogs. Prevention is key. It’s worth noting that a third of all cats diagnosed with heartworm live indoors.

Dogs Have the Same Chance of Contracting Heartworm as Getting Cancer

The difference is, heartworm is almost entirely preventable. Monthly heartworm preventatives are quite good at protecting dogs from the dangers of heartworm disease, even in areas of high prevalence. Even if your dog is on a monthly preventative medication, it’s still important to have him tested annually for heartworm to ensure he doesn’t need any treatment. Heartworms can live inside a dog for up to seven years.