Risk of Exposure to Vector-Borne Pathogens: What to Expect this Year

Pathogens that cause heartworm disease, Lyme disease, ehrlichiosis, and anaplasmosis continue to spread throughout the United States in 2022. Risks have increased due to rehoming of pets, changes in distribution and prevalence of vector populations, changes in wildlife populations and their incursion into newly developed and reclaimed areas, changes in habitat due to natural or human-induced processes, and the short and long-term changes in climatic conditions. Ticks and mosquitoes remain the principal transmitters of pet and human vector-borne pathogens.

The 2022 forecasts, supported by ongoing research, highlight areas where we can do more to lower the risk of exposure of companion animals to vectors of disease. The best preventive measures that veterinarians and their clients can take is to prevent contact between companion animals and these vectors. The foundation of these prevention strategies are recommendations of products that kill and/or repel mosquitoes and ticks, and the practice of year-round heartworm prevention.

Heartworm Forecast

• We expect the high risk of heartworm infection to continue along the Mississippi river, throughout the southern portions of the interior Midwest, and along the Atlantic coast north into Virginia and southern New Jersey. The prevalence of heartworm continues to increase in the mid-Atlantic region, pushing northward into the densely populated regions of the northeast. The number and diversity of mosquitoes teamed with the population densities of the region support that heartworm infections are more likely to affect 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 Indiana, central and northern Illinois, southern Iowa, and Lower Michigan and Ohio in the Great Lakes region.
• Additional areas likely to experience increased risk include the southwest (New Mexico and southern Arizona), large portions of Colorado and Kansas, and the northern Great Plains.
• As reported last year, forecast of increased risk continues in northern California and portions of Idaho and eastern Montana.
• We expect that much of the upper Midwest and the Northeast will have little change, perhaps indicating that increased emphasis on vector control and compliant heartworm prevention are having an impact in these regions. It is important to remember that areas of greater local prevalence and increased risk are likely to remain in some areas within these regions.
• The intriguing increase in risk reported last year in much of central and southern Florida remains. We mentioned in our forecast summaries last year that the pandemic of 2020 may have affected pet disease prevention strategies in many parts of the US. This and other factors discussed above that affect heartworm prevalence may have also affected veterinary visits and testing in this and other regions of emerging risk.
• Very few regions are expected to have lower than average prevalence. As mentioned previously, it is important to remind clients that changes in local environments could create risks that might not be evident in the broader regional forecasts.

Year-round use of preventive products remains the best means of providing comprehensive internal and external parasite control. Annual testing is recommended to monitor compliance and preventive efficacy.

Lyme disease Forecast

The tick vector (Ixodes scapularis) of Lyme disease (Borrelia burgdorferi) continues to expand its geographic range. These ticks (called deer ticks) also transmit other important agents such as Anaplasmaphagocytophilum, Babesia spp., Borrelia miyamotoi, Ehrlichia muris eauclarensis, and possibly Bartonella spp. On-going research is increasing the spectrum of disease agents transmitted by deer ticks.

• The geographic prevalence of Lyme disease continues to expand southward and westward.
• We expect increases beyond last year’s forecasts in eastern Kentucky, northeastern Tennessee, western Michigan, and Ohio. High-risk “hot-spots” are again predicted in northern and western Lower Michigan, and southern and northeastern Ohio.
• High risks of Lyme disease persist in all portions of the Northeast, the upper mid-western states of Wisconsin, Minnesota, and the upper peninsula of Michigan. A higher than normal risk continues in North Dakota, northeastern South Dakota, Iowa, Illinois, and eastern Kentucky.
• The southward movement of Borrelia burgdorferi is also evident in the increasing risk in the Carolinas and Tennessee. Higher risk areas in east central South Carolina and most of coastal North Carolina appear for the first time in the 2022 forecast. These emerging threats validate and emphasize our reminders that pets and pet owners do not have to travel to the traditional endemic areas of the Northeast to encounter substantial Lyme disease risks.

Veterinarians in regions of historically high prevalence and in forecasted regions of increased risk should reinforce their recommendations of aggressive tick control. Keep in mind that potential spread of Lyme Borreliosis can occur anywhere the tick vector is present. Always consider vaccinating high-risk patients. Annual testing can aid in assessing risk for dogs in hyper-endemic areas.

Ehrlichiosis and Anaplasmosis

Forecasts are also provided for these important tick-borne diseases of dogs. View the Ehrlichia spp. and Anaplasma spp. forecasts and learn more about the CAPC guidelines for prevention and treatment of ehrlichiosis and anaplasmosis.

2022 Anaplasma spp. forecast

2022 Ehrlichia spp. forecast

Year-Round Protection and 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 correctly.

CAPC Parasite Prevalence maps and Forecast maps are validated tools for increasing client willingness to engage in parasite prevention. Sign up to receive local alerts on parasite testing results down to the county level today by visiting the CAPC Parasite Prevalence Maps and selecting "Get Updates".

Monthly Pet Parasite Forecasts

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

Flea Forecasts

CAPC now offers a daily Flea Forecast at www.petdiseasealerts.org that displays flea activity across the United States, based on environmental conditions. The Flea Forecasts also offer a unique look at the historical movement of fleas through a video animation, showing changes in flea activity over the previous 12-month period.

The Flea Forecasts are a strong reminder to pet owners to protect pets year-round with flea control products, limiting infestations on pets and preventing establishment of flea populations in the home.

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, a free review can be read here and full access to all of our manuscripts describing the methodology and fidelity of our forecasts can be found here.