Ticks and Tickborne Diseases

(This page is part of a series. For information on other illnesses that can affect NPS employees, volunteers, commercial use providers, and visitors, please see the NPS A–Z Health Topics index.)
Ixodes tick
Ixodes tick.

CDC/ James Gathany; William L. Nicholson, Ph.D.

Ticks are external parasites that feed on the blood of vertebrate species (mammals, birds, reptiles and amphibians) and can cause a range of illnesses in both humans and animals. Most ticks go through four life stages: egg, six-legged larva, eight-legged nymph, and adult. A tick must take in a blood meal to develop to the next life stage (e.g., larva to nymph, nymph to adult). The full life cycle can take up to 3 years. Adult ticks are approximately 3 to 5 millimeters in length (roughly the size of a sesame seed to an apple seed) depending on age, sex, species, and feeding status. Larval and nymphal stage ticks are even smaller. Infected ticks can transmit pathogens (bacteria, viruses, and protozoa) to humans or animals when they bite and attach. The amount of time a tick needs to be attached to transmit the pathogen. In most cases, a tick must be attached for >36 hours for the Lyme disease bacterium to be transmitted, but other pathogens can be transmitted in shorter periods of time. “Hard ticks” have a visible dorsal shield (scutum) and include the black-legged tick (also called the deer tick) Ixodes scapularis, the Lone Star tick (Amblyomma americanum), and Dermacentor ticks, including the American Dog Tick and Rocky Mountain wood tick. Hard ticks can transmit multiple pathogens responsible for diseases such as anaplasmosis, babesiosis, ehrlichiosis, Lyme disease, Rocky Mountain Spotted Fever, tularemia, and Powassan virus disease. Alpha-gal allergy, also known as the "meat allergy," can be triggered by a tick bite, with growing evidence pointing to the bite of the lone star stick. Toxins of ticks (most commonly the Rocky Mountain wood tick and the American dog tick in the U.S.) can also cause a rare condition in animals and humans known as tick paralysis, which usually resolves following removal of the tick. “Soft ticks” (lacking a scutum) can transmit the Borrelia bacteria that cause Tick-Borne Relapsing Fever. Ticks exist throughout the United States, although the type of tick, the pathogens they carry, and the prevalence varies geographically. Complex life cycles that involve the interplay of humans, wildlife, domestic animals, habitat, climate, and socioeconomic factors make tick-borne diseases a true One Health issue.

Humans: Lyme disease is the most common tickborne disease that affects humans in the U.S., with approximately 400,000 cases reported each year, though this number underestimates the true burden of the disease. Other tickborne diseases occur infrequently with just a handful of cases reported each year. The risk for specific tickborne diseases varies based upon the tick vector being present in an area and capable of transmitting a pathogen. A more comprehensive list of tickborne diseases is available in CDC’s Tickborne Diseases of the United States, along with other resources listed below.The most common symptoms caused by tickborne disease include fever, chills, aches, and rash. A thorough history and physical, as well as laboratory testing, can be used to assess for and diagnose infection; however, recognition of tick-borne diseases can sometimes be difficult. Early detection is important, as many tick-borne diseases are treatable with antimicrobials. There are currently no human vaccines for any of the most common tickborne disease in the U.S. However, clinical trials are underway for a new Lyme disease vaccine that may be available to the public in the next few years.

Animals: Ticks feed on a variety of animals, but rodents are the most common reservoir for tick-borne diseases. For some diseases, such as Lyme disease, wildlife (e.g., deer, lizards) provide a source of blood for ticks and maintain their survival but are not actually infected with the disease pathogen. Numerous studies have investigated the role that wild birds play in tick dispersal (including exotic species) and their associated pathogens. Research has demonstrated that some wildlife (i.e., opossums and squirrels) serve as ecological traps, thus reducing tick survival in the environment. Animals are impacted by ticks and suffer from many of the same tickborne diseases as do humans. Infected animals may show no signs of illness or may become seriously ill or die. In addition, smaller-bodied animals with severe tick infestations may experience anemia from blood loss. Tick prevention products are available for dogs, cats, and livestock and include oral, topical, and wearable options. Most dogs and cats will benefit from a tick prevention product, but the risk of tickborne diseases can be discussed further with an animal health professional. A Lyme disease vaccine for dogs is available in the U.S and is recommended for dogs that spend time outdoors in Lyme disease endemic areas (the Northeast and Midwest).

Environment: Hard ticks prefer wooded and brushy areas with high grass and leaf litter. These ticks are more likely to be found on the edge of a trail or off the trail in park settings. Hard ticks are found throughout the United States; this CDC resource provides information on the geographic locations. CDC’s tick surveillance map is an interactive tool that can help you locate the ticks of concern in your area.Soft ticks are found in the western half of the United States, including Texas, and typically live in higher altitudes (1,500 to 8,000 feet) in the West or caves and burrows in the South. Over the last several decades, climate change is thought to play a role in a geographic range expansion of several tick species. Deer management and landscape management practices, such as fire regimes (suppression or controlled burns) may also influence tick ecology.

  • Learn more about whether you live, work, or are traveling in an area of risk. The CDC has some information, but additional information may be available through your local or state health department website.
  • Wear protective clothing and footwear. This may include wearing long sleeves and long pants, tucking pants into socks, and wearing a hat or cap.
  • Hike in the center of trails to avoid brushing up against vegetation and avoid sitting on logs.
  • Wear light-colored clothes so you can easily spot ticks.
  • Use repellent: This EPA resource can help you find the repellent that is right for you.
  • Treat clothing and gear with permethrin.
  • Perform tick checks. Check your body for ticks after being outdoors (especially under the arms, in and around the ears, inside the belly button, back of the knees, in and around the hair, between the legs, and around the waist). Check your clothing (including shoelaces) and gear. Check your pets.
  • Shower soon after spending time in tick habitat.
  • Put clothing on high in the dryer for at least 10 minutes to kill ticks.
  • Prepare and utilize a tick kit: a small first-aid kit that contains everything you need to prevent or remove ticks. Components of a tick kit may include: DEET or another EPA-approved repellent, Permethrin (0.5%) to apply to shoes and clothing, tweezers to remove an embedded tick, rubbing alcohol or soap and water to clean skin after removing tick, and mirrors for employees to inspect themselves for ticks.
  • For employees: Utilize NPS resources (see "Resource" section below) to educate employees and the public on the risk of ticks and how to reduce exposure. Contact the Office of Public Health ( for additional education support.
  • Remove ticks safely using tweezers and pulling upward with steady pressure. Do not twist the tick or try to remove it without a tool. Clean the tick bite area thoroughly and consider keeping the tick in a sealed bag/container for possible future identification or submission.
  • Seek medical attention if you observe any symptoms of tickborne illness. It’s important to communicate the tick bite exposure and timing of symptoms to your medical provider and discuss tick bite prophylaxis or treatment options.
  • (Employees) Report tick bites to your supervisor and as an exposure in SMIS. The report should include details such as location in the park where tick was acquired (if known), location of the tick on the body, and any other relevant specifics. In the case that the reporting individual develops a tickborne disease, the exposure can be updated to an accident report. Contact regional or local safety representatives for questions or concerns related to exposure or accident reporting.
Last updated: April 11, 2023
One Health image
NPS Resources: Other Resources: NPS-related Publications:
  • Martin AM, Buttke D, Raphael J, et al. Deer management generally reduces densities of nymphal Ixodes scapularis, but not prevalence of infection with Borrelia burgdorferi sensu stricto. Ticks Tick Borne Dis. 2023;14(5):102202. doi:10.1016/j.ttbdis.2023.102202
  • Johnson TL, Graham CB, Boegler, et al. Prevalence and diversity of tick-borne pathogens in nymphal Ixodes scapularis (Acari: Ixodidae) in Eastern National Parks. J Med Entomol 2017;54(3):742-751. Available at:
  • Jones E, Chanlongbutra A, Wong D et al. Knowledge, attitude, and practices regarding Lyme disease prevention among employees, day visitors, and campers at Greenbelt Park. Park Science 2016; 32(2):46-53. Available at:
  • Han GS, Stromdahl EY, Wong D, et al. Exposure to Borrelia burgdorferi and other tick-borne pathogens in Gettysburg National Military Park, South-Central Pennsylvania, 2009. Vector Borne Zoonotic Dis 2014;14(4):227-33. Available at:
  • Eisen L, Wong D, Shelus V, et al. What is the risk for exposure to vector-borne pathogens in United States national parks? J Med Entomol 2013;50(2):221-30. Available at:
  • Adjemian J, Weber IB, McQuiston J, et al. Zoonotic infections among employees from Great Smoky Mountains and Rocky Mountain National Parks, 2008-2009. Vector Borne Zoonotic Dis 2012;12(11):922-31. Available at:
  • Chanlongbutra A, Wong D, Khavari K, et al. Prevention of vector-borne diseases at National Park service units in California: results from an employee survey. Available at: Accessed July 31, 2017.
  • Geissler AL, Thorp E, Van Houten C, et al. Infection with Colorado tick fever virus among humans and ticks in a national park and forest, Wyoming, 2010. Available at:

Last updated: June 6, 2023