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July 01, 2021

Parasites pose greater risk to pets in 2021

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The risk of exposure to pathogens causing heartworm disease, Lyme disease, ehrlichiosis, and anaplasmosis continues to increase throughout the United States as ticks and mosquitoes continue to expand their ranges.

The Companion Animal Parasite Council’s annual Pet Parasite Forecast for 2021 released in May highlights areas of concern where more can be done to lower the risk of exposure of companion animals to vectors of disease.

The CAPC forecasts are the work of parasitologists and statisticians to identify regions of the country that may experience higher parasite risks in the months ahead. Numerous factors are analyzed, including the number of positive tests for diseases and the influence of weather patterns, vegetation indices, and human population density.


The prevalence of heartworms is expected to be much higher than in previous years in areas along the Mississippi River, throughout the southern portions of the interior Midwest, and along the Atlantic coast north into Virginia and southern New Jersey, according to the CAPC forecast.

As the prevalence of heartworm continues to increase in the mid-Atlantic region and into the megalopolis regions of the Northeast, heartworm infections are more likely to impact the health of increasing numbers of dogs in those areas.

Veterinarians in states with historically lower prevalence are again cautioned about the increasing risk of heartworm infection and are encouraged to have a discussion with their clients about the changing prevalence. This is particularly important in the interior Midwest—Indiana, central and northern Illinois, and southern Iowa—and lower Michigan and Ohio in the Great Lakes region.

Lyme and other diseases

The geographic distribution of Lyme disease continues to expand southward and westward. Particularly large increases are expected in eastern Kentucky, northeastern Tennessee, western Michigan, and Ohio. High-risk hot spots are predicted in parts of northwestern and southwestern lower Michigan and southern and northeastern Ohio.

The CAPC advises veterinarians in regions of historically high prevalence and in forecasted regions of increased risk to reinforce their recommendations for aggressive tick control.

Additionally, veterinarians in regions where the prevalence of Lyme and other tick-borne diseases is low to moderate are advised to use CAPC forecasts to explain the need for testing and prevention.

The CAPC forecasts also address the spread of ehrlichiosis and anaplasmosis in dogs. Information about these and other tick- and mosquito-borne diseases along with the 2021 forecast are available at their website.