Researchers see steady increases in Lyme and other tickborne diseases
FRANKFORT Team Kentucky is committed to identifying trends in data that impact the health of Kentuckians. When you think of Lyme disease, Kentucky may not be one of the top states you think of as being heavily impacted by this disease. Although we may not see case numbers as high as northeastern states, we are seeing a steady increase in reported cases of Lyme disease, as well as other tickborne diseases, such as spotted fever rickettsiosis and ehrlichiosis.
In Kentucky, tickborne diseases have increased about 128% between 2020 (160 cases) and 2023 (364 cases). Lyme disease alone has shown the greatest percent increase at about 275% from 2020 (32) to 2023 (120). Despite the increase in reported Lyme disease cases, there is still much to learn about the true risk of getting Lyme disease in Kentucky. The Kentucky Department for Public Health (KDPH) is working to improve this knowledge through enhanced tick and Lyme disease surveillance.
Many forces are theorized to contribute to the rise in tickborne diseases in the United States, one of which is the expansion of the geographical range for various vector species, including the blacklegged tick (Ixodes scapularis), the species responsible for the Lyme disease transmission. Biologists studying this topic believe one of the largest contributions to this expansion is the reforestation efforts and reestablishment of the white-tailed deer populations in the eastern US through the 1900s, after the rapid deforestation of land and decimation of the white-tailed deer populations that occurred during European colonization of the eastern US.
Figure 1 from this study (right), depicts the locations of blacklegged tick refuge in the mid to late 1900’s in the northeast and upper Midwest and the presumed direction of range
expansion from these locations until present (Eisen and Eisen, 2023).[1] Of note, many of the arrows point toward Kentucky, which indicates that we should expect to continue seeing increasing numbers of blacklegged ticks, as well as higher rates of reported Lyme disease in the future.
Figure 2 (opposite page), from the Tickborne Disease in Kentucky StoryMap, is a map of Lyme disease case incidence rates by county in Kentucky from 2011 – 2023. [4] The map shows higher rates of reported Lyme disease along the state’s northeastern border with Ohio and West Virginia. The Ohio Department of Health reports 72 out of 88 Ohio counties have established blacklegged tick populations (data from 2010 – 2024), including all of the counties along the Kentucky border.[2] The West Virginia Department of Health reported 42 out of 55 counties had established blacklegged tick populations in 2019.[3] The incidence rates in Kentucky, in conjunction neighboring states’ data, are in-line with the directional expansion trends described in the Eisen and Eisen, 2023 study.
Tick Surveillance
KDPH, in collaboration with the University of Kentucky Department of Entomology (UK-Ent), has been building our tick surveillance capacity since 2019 by actively looking for ticks in their natural environment. Surveillance is typically conducted in early spring through summer months by students with the UK-Ent program and members of the Public Health Protection and Safety (PHPS) branch with KDPH. As of 2024, 19 Kentucky counties have been identified with established populations of blacklegged ticks.
In October, 2024, KDPH collaborated with the Centers for Disease Control (CDC), UK-Ent, and the state and national parks systems, to complete a week of tick surveillance in select Kentucky parks near the northern and southern borders. The primary goal was to see how many blacklegged ticks we could find and if they carried any pathogens. We surveyed 29 sites in 15 counties and collected 162 blacklegged ticks. 160 ticks were tested by the CDC for pathogens, including Borrelia burgdorferi (Lyme), Borrelia miyamotoi (hard tick relapsing fever), other Borrelia species, ehrlichiosis, and anaplasmosis.
Forty ticks tested positive for Borrelia burgdorferi (Lyme) and 2 ticks tested positive for Borrelia miyamotoi (Hard Tick Relapsing Fever[5]), the first identification of this pathogen in Kentucky. These results indicate that blacklegged ticks and tickborne disease pathogens, including Lyme disease, are present in Kentucky. Continued efforts such as this will enhance surveillance capacity and improve data to inform Lyme Disease education to the public of and enhance communications with healthcare providers about the increasing risk of Lyme and other tickborne diseases.
Lyme Disease Surveillance and Providers
Collaboration with healthcare providers is crucial to improving surveillance of human cases of Lyme disease; reporting of this disease can be complicated. Reportable disease cases are classified based on case definition criteria that has been standardized nationally by the CDC’s National Notifiable Diseases Surveillance System (NNDSS). For Lyme disease, the case definition is very specific for both clinical and laboratory criteria. Clinical criteria must include one of the following as reported by a healthcare provider: erythema migrans rash (aka bullseye rash), or involvement of the musculoskeletal, nervous, or cardiovascular system (see the NNDSS Lyme case definition page[6] for more details). These clinical manifestations must be clearly described in the medical records, otherwise the case will not meet the appropriate criteria to be classified as a confirmed or probable case. This is crucial to accurately assess the impact of Lyme disease on Kentuckians and communicate data trends to our healthcare providers. Increased awareness and understanding of Kentucky-specific Lyme disease data will help ensure patients receive timely treatment to avoid the long-term and more severe symptoms that can occur with Lyme disease.
Ultimately, the shared goal of public health surveillance and healthcare is to protect and improve the health of our communities. For Lyme, or any tickborne disease, the most important messages are to prevent tick bites and to seek early treatment. KDPH will continue to make gathering enhanced and timely data a primary goal to increase awareness and inform public health activities.