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Ohio State University Extension


Blacklegged (Deer) Tick, Ixodes scapularis

Agriculture and Natural Resources
Sarah M. Short, PhD, Assistant Professor, Department of Entomology, The Ohio State University
Risa Pesapane, PhD, Assistant Professor, Department of Veterinary Preventive Medicine and School of the Environment and Natural Resources, The Ohio State University
Tim McDermott, DVM, Assistant Professor, Extension Educator, Agriculture and Natural Resources, The Ohio State University
James Radl, PhD Candidate, Department of Entomology, The Ohio State University

Blacklegged ticks, also called deer ticks, are blood-feeding parasites that may infect people, horses, and companion animals with pathogens that cause diseases.

Overhead photos of a nymph female tick, an adult male tick with a dark-colored body, and an adult female tick with an orange-colored body around a dark spot.Preventing tick bites is the best protection from tickborne disease (box 1). If you find a tick biting you, remove the tick as soon as possible (box 2), note the date of the bite, and contact your physician if you develop symptoms (e.g., fever, chills, aches/pains, rash) in the following weeks. You can also save the tick in rubbing alcohol, hand sanitizer, or a sealed container and submit it for species identification. Submission options can be found here (link 1). For more information on tick safety, visit the Ohio Department of Health (link 2).


Two maps of the United States aligned vertically, with the top map showing the distribution of the blacklegged deer tick in 1996, and the bottom map showing the increased distribution of the blacklegged deer tick in 2021.Blacklegged ticks are relatively smaller at all life stages than other medically important ticks. The larval stage of the blacklegged tick is typically smaller than 1 millimeter and has six legs (like all larval ticks). Nymphal-stage blacklegged ticks are about the size of a poppy seed (1.5 millimeters), and unfed adult males and females are about the size of a sesame seed (2–3 millimeters) (CDCa, 2023). The backs of adult male ticks are uniformly covered by a dark brown shield or “scutum.” This shield partially covers the back of the nymph and adult female. The nymphal stage is translucent to slightly gray or brown. The adult female has a red-orange body surrounding the dark brown shield. After they have taken a blood meal, engorged adult females can be as wide as the eraser on the end of a No. 2 pencil (6 millimeters) and may appear gray.

Distribution and Spread

Blacklegged ticks have recently emerged as serious pests in Ohio. Over the past 25 years, they have spread into many new areas of the eastern United States (Figure 2) (CDCb, 2023). Established Ohio populations were first detected in Coshocton County in 2010 (Wang et al., 2014) and are now considered established in 61 Ohio counties (Figure 3) (Ohio Department of Health, 2023). Blacklegged ticks have been reported in nearly every county in Ohio and should be considered a statewide risk, though abundance may vary greatly across different habitats.Map of Ohio showing the distribution of the blacklegged deer tick from 2010 through 2023.

Life Cycle, Activity, and Preferred Habitat

Blacklegged ticks have a life cycle of approximately two years that consists of the following stages: eggs, larva, nymph, and adult (Figure 4) (Ohio Department of Health, n.d.). Larvae are most active in the summer and fall, nymphs are primarily active in the spring and summer, and adults are active in the spring and fall. One or more life stages may be active during every month of the year, depending on temperature. Positive cases of Lyme disease have been reported in Ohio in all 12 months of the year (Ohio Department of Health, n.d.). Because of this yearlong activity, preventive measures should be taken outdoors where ticks occur, even during fall and winter.

Ticks feed only on blood, and blacklegged ticks seek out and feed on a different host during each life stage. Adult blacklegged ticks feed primarily feed on white-tailed deer. Larvae and nymphs feed primarily on small rodents, such as white-footed mice and chipmunks.  Adults and larvae/nymphs are most common in areas where their hosts are located (CDCa, 2023). These areas are primarily in or near forested areas, especially forests with high leaf-litter coverage, but may also include your own backyard, especially shaded areas of lawns.

To find hosts, blacklegged ticks climb low-lying vegetation (approximately 0–3 feet), such as bushes, and latch on when a host brushes past. It is during this behavior (called questing) that ticks will climb onto humans or other animal hosts (CDC, 2011). Ticks do not jump or drop from trees (CDC, 2011).Graphic showing the seasonal activity of blacklegged deer ticks in Ohio from 2010 to 2022.

Pathogens Transmitted by Blacklegged Ticks

Blacklegged ticks are best known for transmitting Lyme disease (link 3). Lyme disease occurs when someone is infected with the bacteria Borrelia burgdorferi (or, rarely, B. mayonii), which is transmitted in the saliva of the tick during feeding (CDCa, 2023). Lyme disease cases have increased 17-fold in Ohio in the past decade (Ohio Department of Health, 2023). Patients with Lyme disease commonly display an expanding red rash at the spot of the tick bite that often resembles a bullseye (though this is not always the case, Figure 6) (CDC, 2021). This rash begins an average of seven days after the bite, but the onset can vary from three to 30 days. Expansion of the rash occurs over several daysMap of Ohio showing the incidence of Lyme disease..

Other symptoms of Lyme disease include fever, chills, headache, fatigue, and achy muscles and joints (CDC, 2021). Only nymphal and adult ticks can transmit the bacteria that causes Lyme, and nymphs are most likely to transmit because their small size makes them difficult to detect and because they are most active at times of year when people are outdoors with exposed skin.

Other diseases that can result from blacklegged tick bites include anaplasmosis (link 4) and ehrlichiosis (link 5), which are caused by infection with the bacteria Anaplasma phagocytophilum and Ehrlichia muris eauclairensis, respectively (CDC, 2022). These ticks can also transmit the parasites that cause babesiosis (link 6). Like Lyme disease, all these diseases commonly cause muscle pain, fever, and headaches. Lyme, anaplasmosis, ehrlichiosis, and babesiosis can all be treated with medication (CDC, 2022).

Blacklegged ticks can also transmit Powassan virus. The first case of Powassan virus disease was reported in Ohio in 2021 (Fauss, 2021). Infection with Powassan virus can cause fever, headache, vomiting, and weakness. Infection of the brain and/or spinal cord occurs in severe cases. These severe cases (termed “neuroinvasive”) are fatal approximately 12% of the time (CDCc, 2023). No medication is available for this virus, and treatment is limited to supportive care.

Two side-by-side photos showing round inflamed skin with dark round “bullseye” in the middle of the inflammation, indicating a tick bite site.Early diagnosis and treatment are important in all cases, so do not ignore symptoms and be sure to promptly seek treatment if symptoms arise.

How can I protect myself?

  1. Prevent tick bites (box 1).
  2. Remove biting ticks promptly (box 2).
  3. Record the date of the bite and save the tick in rubbing alcohol, hand sanitizer, or a sealed baggie.
  4. If symptoms develop, seek medical care.

Consider submitting your tick for identification to your local health department or sending a photo to TickSpotters (link 1).


Box 1: Tick Bite Prevention

1. Hike at the center of trails and avoid tall vegetation when possible.

2. Wear light-colored clothing, minimize exposed skin, and tuck pants into socks.

3. Wear permethrin-treated clothing (link 7).*

4. Apply repellent to skin and/or clothing.* To find a repellent for you, visit

5. Perform frequent tick checks during and after time spent outdoors (link 8).

6. Shower as soon as possible after spending time outdoors.

7. To protect pets, talk to your veterinarian about anti-tick products.

*Read the label instruction carefully to ensure safe and effective application.


Box 2: How to Remove a Tick

1. Using pointy tweezers or a tick-removal tool, grab the tick as close to the skin as possible.

2. Pull straight upward with steady, even pressure.

3. Save the tick in rubbing alcohol, hand sanitizer, or a sealed container/bag.

4. Wash hands, the bite site, and the tools with soap and water.

The Knowledge Exchange in The Ohio State University College of Food, Agricultural, and Environmental Sciences has created a landing site to host knowledge on ticks, mosquitos, and other blood-feeding arthropods. You can find this site at or here (link 11). More information on ticks and tick-borne diseases is also available at


  1. Tick Spotters, TickEncounter—
  2. Tickborne Diseases in Ohio, Ohio Department of Health—
  3. Lyme Disease, Centers for Disease Control and Prevention (CDC)—
  4. Anaplasmosis, CDC—
  5. Ehrlichiosis, CDC—
  6. Babesiosis, CDC—
  7. Permethrin general fact sheet—
  8. How to do a tick check, Tickencounter—
  9. Blacklegged tick (Ixodes scapularis) surveillance—
  10. Lyme Disease, Ohio Department of Health—
  11. The BITE SITE, Knowledge Exchange—


Centers for Disease Control and Prevention (CDCa). (2023, January). Lyme disease, transmission.

CDCb. (2023, April). Blacklegged tick (Ixodes scapularis) surveillance.

CDCc. (2023, June). Powassan virus.

CCD. (n.d.). Public health image library (PHIL).

CDC. (2011, April). Lifecycle of blacklegged ticks.

CDC. (2021, January). Signs and symptoms of untreated Lyme disease.

CDC. (2022, August). Tickborne diseases of the United States.

Fauss, L. (2021, December). Powassan virus disease detected in Columbiana county [Press Release]. Columbiana County Health District.

Ohio Department of Health. (n.d.). Tickborne diseases in Ohio.

TickEncounter. (2023). How to do a tick check: tips for you and your pet [Video]. YouTube.

Wang P., Glowacki M. N., Hoet A. E., Needham G. R., Smith K. A., Gary R. E., & Li X. (2014). Emergence of Ixodes scapularis and Borrelia burgdorferi, the Lyme disease vector and agent, in Ohio. Frontiers in Cellular and Infection Microbiology, 4(70).

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Originally posted Feb 29, 2024.