Is Lyme Disease Common in Kentucky? What Studies Show

Lyme disease occurs in Kentucky
Studies have identified infected wildlife and blacklegged ticks in the state
These findings confirm an ongoing risk of Lyme disease

Is Lyme disease common in Kentucky? Kentucky has historically been considered a lower-incidence state than the Northeast, but research has shown that Borrelia burgdorferi, the bacterium that causes Lyme disease, circulates in both wildlife reservoirs and blacklegged ticks within the state. Although reported human case rates remain lower than in highly endemic regions, Kentucky residents can be exposed to infected ticks and should take appropriate precautions.

What have studies found in Kentucky?

Evidence for Lyme disease in Kentucky comes from human case reports, wildlife studies, and statewide tick surveillance.

A review of Kentucky Lyme disease reports from 1985 through 1990 identified 51 cases that met the case definition. Although the recognized tick vectors had not yet been identified in Kentucky, the authors concluded that physicians should educate patients about Lyme disease risk and methods to prevent tick bites.¹

In their study, Buchholz and colleagues from Western Kentucky University found that more than half of the mice they tested in Kentucky were positive for Borrelia burgdorferi. They also discovered that the prevalence of B. burgdorferi was higher in tissue samples than in blood—a finding consistent with previous studies.

“Overall prevalence of B. burgdorferi in mammals examined by blood sampling was 21.8%, while prevalence in tissues was 63.5%,” wrote Buchholz.²

The prevalence of infected mammals was similar to that reported in other southeastern U.S. states. Studies in Georgia, Florida, and South Carolina reported prevalence rates ranging from 6.5% to 41.8%. Meanwhile, 25% to 37% of small mammals in Virginia were infected with Borrelia burgdorferi.^4,5

Buchholz and colleagues also noted that infestation of these small mammals by Ixodes scapularis, the primary Lyme disease vector in the eastern United States, was uncommon at their study sites. These findings help explain why Kentucky has historically reported fewer human Lyme disease cases than highly endemic states despite evidence of infected wildlife.²

More recent statewide surveillance has confirmed that infected blacklegged ticks are present in Kentucky. Between March 2019 and December 2020, researchers identified 457 Ixodes scapularis ticks from 32 Kentucky counties. Borrelia burgdorferi was detected in tick populations collected from 14 counties. The investigators also noted that reported human Lyme disease cases in Kentucky increased by more than 300% between 2010 and 2019.³

These surveillance studies likely underestimate the true distribution of infected ticks because only selected counties and collection sites were sampled. Likewise, reported human Lyme disease cases may not capture every infection, particularly when patients are not tested, are diagnosed elsewhere, or are not reported through public health surveillance.

Why do mice matter?

Mice and other small mammals serve as important reservoirs for Borrelia burgdorferi. They do not transmit Lyme disease directly to people. Instead, blacklegged ticks become infected while feeding on infected animals and may later transmit the bacteria to humans through a tick bite.

Together, the wildlife and tick surveillance studies demonstrate that the Lyme disease bacterium is established in parts of Kentucky, even though the state’s overall incidence remains lower than that of the Northeast.

What do these findings mean for Kentucky residents?

The available evidence shows that Lyme disease should be considered in Kentucky residents with compatible symptoms and a history of tick exposure. Prompt tick removal, recognition of an expanding erythema migrans rash, and early medical evaluation remain important. Preventive measures are especially important for people who spend time outdoors in wooded or grassy areas.

Frequently Asked Questions

Is Lyme disease common in Kentucky?

Lyme disease occurs in Kentucky, although reported case rates remain lower than in highly endemic northeastern states. Studies documenting infected wildlife and infected blacklegged ticks confirm that Lyme disease transmission can occur within the state.

Do mice carry Lyme disease in Kentucky?

Yes. Studies have identified Borrelia burgdorferi in mice and other small mammals in Kentucky. These animals serve as reservoirs for the bacteria that infect blacklegged ticks.

Can you get Lyme disease directly from a mouse?

No. Lyme disease is transmitted through the bite of an infected blacklegged tick, not through direct contact with mice.

Do blacklegged ticks in Kentucky carry Lyme disease?

Yes. Statewide surveillance detected Borrelia burgdorferi in blacklegged tick populations collected from 14 Kentucky counties. Although the risk varies by location, infected ticks have been documented within the state.

Clinical Takeaway

Research conducted over the past several decades demonstrates that Lyme disease is present in Kentucky. Human case reports, infected wildlife reservoirs, and statewide tick surveillance all support the conclusion that residents can be exposed to infected blacklegged ticks.

Although Kentucky remains a lower-incidence state than the Northeast, clinicians and residents should recognize that Lyme disease is an established risk and emphasize tick-bite prevention and early diagnosis.

Related Articles

Lyme Disease Symptoms Guide
The Many Forms of Lyme Disease Rashes
Tick Facts: What You Need to Know
Why Early Lyme Disease Tests Can Be Negative

References

1. Pelletier AR, Finger RF, Sosin DM. The epidemiology of Lyme disease in Kentucky, 1985-1990. J Ky Med Assoc. 1991;89(6):266-269.
2. Buchholz MJ, Davis C, Rowland NS, Dick CW. Borrelia burgdorferi in small mammal reservoirs in Kentucky, a traditionally non-endemic state for Lyme disease. Parasitol Res. 2018;117(4):1159-1167.
3. Pasternak AR, Palli SR. Mapping distributions of the Lyme disease vector, Ixodes scapularis, and spirochete, Borrelia burgdorferi, in Kentucky using passive and active surveillance. Ticks Tick Borne Dis. 2022;13(2):101885.
4. Oliver JH Jr, Lin T, Gao L, et al. An enzootic transmission cycle of Lyme borreliosis spirochetes in the southeastern United States. Proc Natl Acad Sci U S A. 2003;100(20):11642-11645.
5. Sonenshine DE, Ratzlaff RE, Troyer J, et al. Borrelia burgdorferi in eastern Virginia: comparison between a coastal and inland locality. Am J Trop Med Hyg. 1995;53(2):123-133.

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Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention