Heartworm, Lyme Disease Forecast Looks Gloomy


The Companion Animal Parasite Council predicts that heartworm and Lyme disease incidence rates will increase across many regions of the country in 2018.

Each year, the Companion Animal Parasite Council (CAPC) releases an annual parasite forecast for the upcoming year. For 2018, the forecast does not look optimistic.


  • Prevalence of Feline Heartworm Infection in the United States
  • Lyme Disease: Companion Animal Parasite Council

These annual forecasts are created by the collective expert opinions of academic parasitologists and are based on factors such as temperature, precipitation, and population density. According to the CAPC, heartworm disease will continue to “aggressively spread” across the United States, and Lyme disease will grow in prevalence in areas east of the Rockies throughout 2018.


Last year, American Heartworm Society President Chris Rehm, Sr, DVM, told American Veterinarian® that it was highly possible that growth in mosquito populations would lead to increases in heartworm transmission in the future. “Higher incidence rates could very well be expected in 2017—and perhaps even more so in 2018,” he continued.

Heartworm disease did rise in 2017, according to CAPC statistics, and the parasite forecast for this year is likely to back up his sentiment about 2018.

The hot, wet weather, coupled with the shifting weather patterns the United States has experienced over the past 2 years, has created ideal breeding conditions for mosquitoes. The CAPC also noted that many unknown heartworm positive dogs have been relocated across the country following last year’s hurricanes, potentially adding to the spread of the disease.

The CAPC points out the following about the predicted geographic spread of heartworm disease this year:

  • Heartworm infections are expected to be above average nationwide.
  • The lower Mississippi River region is a hyper-endemic region, meaning prevalence will be much more active than normal.
  • Northern tier states—from Washington to Vermont—may experience a problematic rise in heartworm infections.

Lyme Disease

The number of Lyme disease cases in humans has tripled over the past 20 years, and the disease continues to rise in prevalence among our furry counterparts. But while infection in dogs occurs more commonly in areas with dense populations of ticks—New England, along the East Coast, and in the upper Midwestern and West Coast states—the CAPC predicts that non-endemic areas will start to see a rise in Lyme disease cases.

As the white-tailed deer population grows across the country and migratory birds carry ticks from endemic to non-endemic areas, pet owners and veterinarians need to be prepared.

The CAPC points out the following about the predicted geographic spread of Lyme disease in 2018:

  • Previously non-endemic areas, such as North Dakota, South Dakota, Iowa, Missouri, southern Illinois, Ohio, Kentucky, Tennessee, and North Carolina, need to be aware of the potential spread of Lyme disease.
  • Western Pennsylvania, eastern Ohio, West Virginia, and the Appalachian region in Virginia will reportedly have an active year.
  • A less active year is being predicted for areas from Washington, DC to Philadelphia, Pennsylvania and eastward, as well as the Boston/Cape Cod, Massachusetts region.

Other Parasites

While the biggest concerns this year are heartworm and Lyme disease, the CAPC points out 2 other parasitic diseases that may cause trouble.


The CAPC says the prevalence of this tick-borne disease is forecasted to be average for much of the United States; except for Minnesota, which is expected to have an active year. Conversely, the Wisconsin/Minnesota border area and the Boston/Cape Cod region should see less activity than normal.


While challenging to geographically forecast each year, ehrlichiosis is expected to be more prevalent than normal in the southern Virginia and northern North Carolina regions. For the rest of the United States, the CAPC forecasts normal prevalence of the disease for the year.

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