Despite the availability of preventative measures – the risk of vector-borne disease remains high in 2019

Endemic areas of heartworm disease, Lyme disease, ehrlichiosis, and anaplasmosis are all expected to have higher than average prevalence in 2019. Despite the availability of acaricides against ticks, heartworm chemoprophylaxis, and vaccines against the causative bacteria of Lyme disease, the prevalence of these diseases in these regions is still increasing.

The 2019 national forecasts for these pathogens highlight the biggest areas of concerns for veterinarians and pet owners alike.

Heartworm Forecast

20190402 Capc Forecast Maps Display Heartworm
  • The prevalence of canine heartworm is predicted to be higher than average throughout the southcentral and southeastern states. The areas of greatest concern are those along the Mississippi River from northern Louisiana all the way into Illinois. Veterinarians in these and neighboring states, and those along the south Atlantic coast should take extra care this year to recommend year-round heartworm preventatives, annual testing, and educate their clients on limiting their pet’s exposure to mosquitoes.
  • Of great concerns are those areas with historically lower prevalence of heartworm that are now seeing an increase in heartworm prevalence. These include Indiana, Illinois, and Iowa. In these areas, clients should be made aware of the increased risk to their pets.
  • The only areas in the United States predicted to see lower than average heartworm prevalence is southern Louisiana, and small areas along the southern Texas border. Lower prevalence is a promising indication of the efficacy of preventative measures, however, thousands of dogs are still exposed every year in these areas and it is still within the highest risk region in the United States, so continued preventative care is imperative to maintain this trend.

The increase in heartworm activity supports CAPC’s recommendation that all dogs be given heartworm preventatives year-round, and tested annually for both heartworm antigens and microfilariae.

Lyme Forecast

20190402 Capc Forecast Maps Display Lyme

The tick vector of Borrelia burgdorferi, an agent of Lyme disease in dogs, is expanding its range from the northeastern and mid-Atlantic states, the upper Midwestern states, and throughout Canada. These ticks are bringing their associated pathogens along for the ride. These include Anaplasma phagocytophilum, Babesia spp., Borrelia miyamotoi, Ehrlichia muris eauclarensis, and possibly Bartonella spp. among others.

  • The seroprevalence of B. burgdorferi is predicted to be higher in three areas this year. Most notably throughout the Appalachian region. Veterinarians ineastern Pennsylvania, West Virginia, western Virginia and North Carolina, and eastern Ohio and Kentucky should reinforce their recommendations on the use of tick preventatives and may consider vaccination for high-risk patients.
  • Second, a hotspot of higher than average seroprevalence is expected to be seen in northwestern Minnesota.
  • Third, although small, areas in Indiana are expected to see higher than average seroprevalence. This is not a historically endemic state, so veterinarians should educate themselves and their clients about the risks of tick-borne disease.
  • The Atlantic coast, New England states, central Wisconsin, and southeastern Minnesota are all expected to see lower than average seroprevalence in 2019.

Preventing exposure to ticks is the best way to prevent infection with tick-borne pathogens. The areas highlighted above expected to see lower than average seroprevalence are endemic for Borrelia burgdorferi and risk for exposure is high!

Ehrlichiosis and Anaplasmosis

View the Ehrlichia spp. and Anaplasma spp. forecast and learn more about the CAPC guidelines for prevention and treatment of ehrlichiosis and anaplasmosis.

2019 Anaplasma spp. forecast

2019 Ehrlichia spp. forecast

Year-round protection, annual testing

The best way to protect your patients is to advise owners of the importance of year-round prevention, even during the winter months. You can use the CAPC Parasite Prevalence Maps to support your recommendation by underscoring the risks in your area and in regions of the country your clients may travel with their pets. It is also critical to emphasize the importance of compliance and using products according to label. The use of CAPC Parasite Prevalence maps and Forecast maps are a validated tool for increasing client willingness to engage in parasite prevention. Sign up for local alerts today by visiting the CAPC Parasite Prevalence Maps and selecting "Get Updates".

Veterinary professionals and pet owners who want to monitor the activity in their county throughout the year, can also access 30-Day Parasite Forecast Maps at These maps, developed exclusively by CAPC, provide a local forecast for every county in the continental United States on a monthly basis.

The Science behind the Forecasts

Vector-borne disease is dynamic and ever changing, driven by multiple factors that affect the development of arthropod vectors and the pathogens they carry. Leading parasitologists work in collaboration with a team of statisticians to identify regions of the country that may experience higher parasite incidence in the months ahead. Numerous factors are analyzed, including the number of positive tests and the influence of weather patterns, vegetation indices, and human population density. Using this multi-disciplinary approach, we are leveraging everyone’s expertise to focus on a single common interest: forecasting the risk of exposure to vector-borne pathogens. While these forecasts predict the potential risk of a dog testing positive, they do not necessarily reflect the occurrence of clinical disease.

To learn more about the science behind the maps, full access to our manuscripts describing the methodology and fidelity of our forecasts can be found here.

We are committed to publishing our scientific studies in open-access journals so they are freely available to researchers, veterinarians, and the general public. For those interested in learning more about the science of these forecasts or to see additional graphics, we encourage you to view them here:


Bowman DD, Liu Y, McMahan CS, Nordone SK, Yabsley MJ, Lund RB. Forecasting United States heartworm Dirofilaria immitisprevalence in dogs. Parasit Vectors. 2016 Oct 10;9(1):540.

Wang D, Bowman DD, Brown HE, Harrington LC, Kaufman PE, McKay T, Nelson CT, Sharp JL, Lund R. Factors influencing U.S. canine heartworm (Dirofilaria immitis) prevalence. Parasit Vectors. 2014 Jun 6;7:264

Brown HE, Harrington LC, Kaufman PE, McKay T, Bowman DD, Nelson CT, Wang D, Lund R. Key factors influencing canine heartworm, Dirofilaria immitis, in the United States. Parasit Vectors. 2012 Oct 30;5:245.

Tick-borne pathogens:

Stich RW, Blagburn BL, Bowman DD, Carpenter C, Cortinas MR, Ewing SA, Foley D, Foley JE, Gaff H, Hickling GJ, Lash RR, Little SE, Lund C, Lund R, Mather TN, Needham GR, Nicholson WL, Sharp J, Varela-Stokes A, Wang D. Quantitative factors proposed to influence the prevalence of canine tick-borne disease agents in the United States. Parasit Vectors. 2014 Sep 4;7:417.

Watson SC, Liu Y, Lund RB, Gettings JR, Nordone SK, McMahan CS, Yabsley MJ. A Bayesian spatio-temporal model for forecasting the prevalence of antibodies to Borrelia burgdorferi, causative agent of Lyme disease, in domestic dogs within the contiguous United States. PLoS One. 2017 May 4;12(5):e0174428.

Liu Y, Lund RB, Nordone SK, Yabsley MJ, McMahan CS. A Bayesian spatio-temporal model for forecasting the prevalence of antibodies to Ehrlichiaspecies in domestic dogs within the contiguous United States. Parasit Vectors. 2017 Mar 9;10(1):138.

McMahan CS, Wang D, Beall MJ, Bowman DD, Little SE, Pithua PO, Sharp JL, Stich RW, Yabsley MJ, Lund RB. Factors associated with Anaplasmaspp. seroprevalence among dogs in the United States. Parasit Vectors. 2016 Mar 22;9:169.

Liu Y, Watson SC, Gettings JR, Lund RB, Nordone SK, Yabsley MJ, McMahan CS. A Bayesian spatio-temporal model for forecasting Anaplasmaspecies seroprevalence in domestic dogs within the contiguous United States. PLoS One. 2017 Jul 24;12(7):e0182028.