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Lyme Disease

Blacklegged tick

Lyme disease is caused by an infection with a bacterium called Borrelia burgdorferi.  In Ohio, B. burgdorferi is transmitted to humans through the bite of an infected blacklegged tick, Ixodes scapularis.

Lyme disease cases are increasing in Ohio as the range of blacklegged tick populations continues to expand in the state and encounters with this tick occur more frequently, particularly in the forest habitats preferred by this tick.

Most humans are infected through the bites of immature ticks calls nymphs.  Nymphs are tiny (less than 2 mm) and difficult to see; they feed during the spring and summer months.  Adult ticks can also transmit Lyme disease bacteria, but they are much larger and are more likely to be discovered and removed before they have had time to transmit the bacteria.  Adult blacklegged ticks are most active during the cooler months of the year.

The best way to prevent Lyme disease is to prevent tick bites.

If you find a tick on your body, remove it quickly to reduce the risk of contracting Lyme disease.  See a healthcare provider if you do get sick.  Lyme disease is curable.  Early diagnosis and treatment are important in order to avoid further health problems related to Lyme disease.

Where does Lyme disease occur in Ohio?

Blacklegged ticks that carry Lyme disease are most commonly found in the eastern and southern areas of the state, but are likely to occur in suitable wooded habitat throughout most or all of Ohio.  On the map below, each dot represents one case of Lyme disease and is placed randomly in the patient's county of residence.  The presence of a dot does not necessarily mean that the Lyme disease infection was acquired in Ohio.  The place of residence can be different from the place where the patient became infected.

Map: Lyme disease in Ohio (2021: 537 cases)

What are the symptoms of Lyme disease?

Early symptoms of Lyme disease typically begin three to 30 days after a tick bite and can include:

  • Erythema migrans rash ("bull's eye" rash)Erythema migrans (EM) rash
  • Headache
  • Fever
  • Chills
  • Muscle pain
  • Joint pain
  • Fatigue

Many of these symptoms are not specific to Lyme disease and can be caused by a variety of different factors.  However, the erythema migrans (EM) rash is often characteristic of Lyme disease.  This is a rash that often begins at the site of the tick bite and gradually expands.  The center of the rash may clear as it enlarges, giving it the appearance of a bull's eye or target.  The rash usually appears within seven to 14 days after the tick bite.  The rash may be warm, but it is usually not painful or itchy.  See photos of what an EM rash looks like on the Centers for Disease Control and Prevention (CDC)'s website.

While the EM rash is commonly associated with Lyme disease, not everyone infected with Lyme bacteria will develop a rash.  About 30 percent of confirmed cases of Lyme disease reported to the CDC do not have an EM rash at the time of their diagnosis.  These cases report joint pain and/or joint swelling at the time of their diagnosis more frequently than cases with an EM rash.  For more information, see CDC's Lyme disease signs and symptoms.

How is Lyme disease diagnosed?

Lyme disease can only be diagnosed by a healthcare provider.  A blood specimen may be collected for laboratory testing.  Please visit the CDC's website for information on diagnosis and testing.

What is the treatment for Lyme disease?

Please visit the CDC's website for additional information on treatment for Lyme disease.

Who is at risk in Ohio?

Anyone who spends time outdoors can be at risk for Lyme disease.  The tick that transmits Lyme disease in Ohio, the blacklegged tick, is most often found in wooded, brushy areas.  People who frequent these settings (hikers, campers, hunters, farmers, gardeners, landscapers, other outdoor workers) may be at increased risk of contracting Lyme disease.

However, it does not take a hike in the forest to encounter blacklegged ticks.  The property around many homes can also provide suitable habitat for ticks, particularly those in yards that are next to woods or brushy areas or those with tall grass or leaf litter.  That is why it is important to take the necessary steps to prevent tick bites.

Ohioans of all ages get sick with Lyme disease, but data collected by the Zoonotic Disease Program suggest that males are more at risk for Lyme disease than females.  Boys between the ages of ten and 14 years appear to be at particularly high risk.  Many cases of Lyme disease are reported in females between the ages of five and nine.

Graph: Lyme disease by age and sex in Ohio

What time of year are Ohioans at risk for contracting Lyme disease?

In Ohio, cases of Lyme disease are reported in every month of the year.  However, the number of reported cases is lowest in the winter, gradually rises in the spring, peaks in the summer, then declines through late summer and autumn.

It can take anywhere from three to 30 days from when the tick bite occurs to when symptoms of Lyme disease appear.  Since most cases get sick in July and August, that means most cases are bitten by an infected blacklegged tick between June and July.  Therefore, late spring through mid-summer is the time of year when Ohioans are most at risk for contracting Lyme disease.

Graph: Lyme disease by week of illness onset in Ohio

What are the trends over time?

Reports of Lyme disease used to be an uncommon occurrence in Ohio.  In the early 1990s, the Health Department reported one to two dozen cases in Ohio residents.  Since that time, the number of reported cases has increased substantially.  It is now common to see over 100 confirmed cases each year.

Table: Lyme disease annual case statistics in Ohio

How can I reduce my risk of Lyme disease?

Steps to prevent Lyme disease include using insect repellent, removing ticks promptly, applying pesticides and reducing tick habitat.  The tick that transmits Lyme disease can occasionally transmit other tickborne diseases as well.

What are the roles of other animals in Lyme disease transmission?

Deer Deer are not directly involved with Lyme disease transmission.  However, they are the preferred host of the adult blacklegged tick and are therefore important in maintaining tick populations.
Dogs Dogs are susceptible to tick bites and tickborne diseases like Lyme disease.  Lyme disease infections in dogs are not a significant risk factor for human infection because dogs (like humans) are considered "dead-end" hosts for the bacteria (i.e., humans cannot get Lyme disease from dogs).  However, dogs can bring infected ticks into the home.
Rodents Rodents, especially deer mice (Peromyscus maniculatus) and white-footed mice (P. leucopus) are important hosts for Lyme disease pathogens.  Juvenile ticks become infected with Lyme disease bacteria when they feed on infected mice.  The ticks may then pass the infection on to future hosts, including humans and pets.
Ticks Ticks, specifically the blacklegged tick, Ixodes scapularis, acquire Lyme disease bacteria from rodents.