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Lyme DiseaseBlacklegged Tick

Lyme disease is caused by the bacterium Borrelia burgdorferi and is transmitted to humans through the bite of infected blacklegged ticks.  Typical symptoms include fever, headache, fatigue and a characteristic skin rash called erythema migrans (the “bull’s-eye” rash).  If left untreated, infection can spread to the joints, heart and nervous system.  Lyme disease is diagnosed based on symptoms, physical findings (e.g., rash) and the possibility of exposure to infected ticks; laboratory testing is helpful if used correctly and performed with validated methods.  Most cases of Lyme disease can be treated successfully with a few weeks of antibiotics.  Steps to prevent Lyme disease include using insect repellent, removing ticks promptly, applying pesticides and reducing tick habitat.  The ticks that transmit Lyme disease can occasionally transmit other tick-borne diseases as well.

Lyme disease occurs primarily in the Northeastern and upper Midwestern United States.  Ohio is located between these two endemic regions and reported fairly low occurrence of Lyme disease in the past.  The low occurrence of Lyme disease cases in Ohio was attributed to the absence of the tick vector, Ixodes scapularis, known as the blacklegged tick or deer tick.

Since 2010, blacklegged tick populations in Ohio have increased dramatically, and their range continues to expand in the state, particularly in the forest habitats preferred by this tick.  The latest map of blacklegged ticks in Ohio is below:

Blacklegged Ticks & Lyme Disease in Ohio Map
(Clicking on the image will open a larger, printable version of the map.)

Unlike other ticks in Ohio, at least one of the three life stages (larva, nymph, adult) of the blacklegged tick is active during all but the very coldest days of winter.  See the blacklegged tick activity chart below:

Blacklegged Tick Activity in Ohio Chart
(Clicking on the image will open a larger, printable version of the chart.)

Human and pet encounters with this tick are sure to increase, and the number of Lyme disease cases may also rise if prevention measures are not taken for both people and pets (see current human case map).  In addition to Lyme disease, the blacklegged tick is also the vector of human granulocytic anaplasmosis and human babesiosis.  It is possible in some areas for the tick to be infected with more than one of these pathogens.

Animals associated with Lyme disease in Ohio include:

  • 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 tick-borne diseases like Lyme disease.  Lyme disease infections in dogs, however, are not a significant risk factor for human infection because dogs (like humans) are considered to be "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.

Lyme disease resources:

Ohio statistics and maps:


Disease reporting and surveillance: 

Fact sheets:

Tick-borne disease prevention literature:


Page Updated:  01/30/2018

Zoonotic Disease Program