Parasites on the Move

Tick-borne diseases continue to expand south and west, CAPC reports.

Tick-borne diseases Lyme and anaplasmosis continue to expand south and west in the United States with the Upper Midwest and Northeast continuing to be high risk areas, according to the Companion Animal Parasite Council in its 2025 Parasite Forecast.

The Companion Animal Parasite Council (CAPC) has released its 2025 Pet Parasite Forecast, highlighting the continued spread of parasitic diseases affecting both pets and humans across the United States. The forecast underscores the importance of proactive prevention measures, including annual testing and year-round parasite control.

Key findings from the 2025 forecast included:

Expansion of tick-borne diseases. Diseases transmitted by ticks, such as Lyme disease, anaplasmosis, and ehrlichiosis, are advancing into new regions. Lyme and anaplasmosis continue to expand south and west in the United States with the upper Midwest and northeast continuing to be high risk areas. Ehrlichiosis, also spread by ticks, remains high throughout the southeast, with continued northward expansion in the upper Midwest and the New England region.

Heartworm disease spread. Mosquitoes are increasingly spreading heartworm disease in the southeastern United States, where the highest risks are found along the Atlantic coast and northward along the Mississippi river. This puts much of the middle of the United States, from Kansas to Maryland, at a heightened risk for heartworm infection. In addition, there are growing areas of increased risk in New Mexico, Colorado, Wyoming, Montana, North Dakota and Northern California.

Emerging threats from new vectors. The invasive Asian long-horned tick is expanding its geographic range in the U.S., introducing new challenges in disease transmission. The full pathogen transmission potential of this tick remains unknown, necessitating increased vigilance.

Environmental and human factors influencing spread. Factors such as rehoming of pets, urbanization, changes in wildlife host and vector densities, and climatic conditions are contributing to the increased spread of parasitic diseases.

“Because dog health helps us predict human health, our monthly, county-by-county forecasts are a crucial health tool for communities,” said CAPC CEO Christopher Carpenter, DVM, MBA. “Each year, we see a growing need for education and preventive care to curb the spread of these diseases. By leveraging the power of our extensive canine surveillance data, we help veterinarians and pet owners take proactive steps to safeguard animal and human health. We hope our forecasts spark meaningful conversations about how we can collectively lower disease risk.”

Recommendations for pet owners and veterinarians

CAPC emphasizes the need for comprehensive prevention strategies to protect pets and humans from parasitic diseases:

• Annual testing. Regular testing of pets for parasites is crucial, even if they are on preventive medications.
• Year-round preventive measures. Consistent use of products that kill or repel mosquitoes and ticks can significantly reduce the risk of infection.
• Vaccinations. Ensuring pets are up-to-date on vaccinations can provide additional protection against certain diseases.
• Education and awareness. Pet owners should stay informed about local parasite risks and consult with veterinarians to develop tailored prevention plans.

“CAPC’s annual forecasts for Lyme, heartworm, anaplasmosis and ehrlichiosis should serve as a call to action for veterinarians and pet owners,” said Dr. Rick Marrinson, Board member/past president for CAPC and practitioner in Longwood, Florida. “In historically endemic regions, these maps reinforce the importance of continued vigilance in testing and prevention. Meanwhile, in areas where these diseases are emerging, veterinarians should adopt new protocols to address the real and growing threats facing pets and people in their communities.”

Accessing the forecast and local alerts

CAPC provides 30-Day Pet Parasite Forecast Maps at petdiseasealerts.org, offering county-by-county updates to help pet owners understand immediate threats in their neighborhoods. These forecasts are developed through collaboration between parasitologists and statisticians, analyzing factors like temperature, precipitation and population density to predict parasite prevalence.

Map info: Companion Animal Parasite Council

Photo credit: istockphoto.com/Andreas Häuslbetz