10 Hottest Cities for Heartworm Disease

Heartworm in Dog
Published: 12/06/17

What do San Francisco, Washington DC, and Las Vegas all have in common?  They’re all popular destinations for people – and heartworms. As you’ll see in the list below, these cities are among the 10 places with the largest increase in heartworm disease, according to September data from the Companion Animal Parasite Council (CAPC), an independent group of scientists, parasitologists and veterinarians who monitor disease rates in pets. 

CAPC Risk Prevalance Map - Source of data
  1. 1.   Las Vegas, NV
  2. 2.   San Francisco, CA
  3. 3.   Paterson, NJ
  4. 4.   Washington, DC
  5. 5.   Providence, RI
  6. 6.   Salem, OR
  7. 7.   Modesto, CA
  8. 8.   Boise, ID
  9. 9.   Oxnard, CA
  10. 10. Thousand Oaks, CA

While the 10 cities might seem random, their locations actually provide clues about the heartworm risk your dogs and cats are facing. Here’s what the clues are telling us.

Message 1: Heartworms are on the move

Heartworms are worms that live in a pet’s heart and cause heartworm disease. Many people think of heartworm disease as something that only affects dogs and cats living in a specific region of the U.S., but the cities on the list span the country from coast to coast. This tells us that heartworm disease is no longer an isolated concern. Pet owners across the country need to be aware of the risk to dogs and cats. 

Message 2: The West is getting wild

More than half the states on CAPC’s Top 10 list are in the western part of the country, which is a surprise. Why? Because these states tend to be dry. Heartworm disease has been known to affect dogs and cats living in the Southeastern part of the country, especially in states like Florida, Louisiana and Georgia. This wet, warm part of the U.S. is perfect for mosquitoes, which are the carriers of heartworm disease. Mosquitoes might not be top of mind in Western states like California, Nevada, Idaho and Oregon, so pet owners and veterinarians might not have heartworm disease on their radar. Data from the CAPC parasite risk maps, though, clearly shows that dogs and cats all over the country are at risk of heartworm disease. 

Message 3: Pets need protection

Heartworm disease is almost always preventable. Unfortunately, if a dog or cat gets heartworm disease, it can be fatal. That’s why CAPC recommends that all pets get treated with year-round heartworm prevention. The Top 10 list of cities shows that preventive treatment is important for dogs and cats all across the country. (CAPC updates the Top 10 list every month, so click here to see of your city made the latest list.)

Message 4: The trend could continue

While there’s no clear-cut reason for the spread of heartworm disease, there are some possible causes. For example, when large numbers of pets must be moved out of states hit by natural disasters like hurricanes, heartworm disease can move with them. Also, more people are traveling with their pets and may visit places where mosquitoes and heartworm disease are a threat. There are also changing weather patterns, new mosquito species emerging in the U.S., and people and pets living closer to wildlife that carries heartworm disease.

Regardless of whether your city is on the list, there’s good news. Here on, you can learn more about heartworm disease and the Bayer products that can help you protect your dog or cat




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