Ticks and Tickborne Diseases: A Guide for Park Visitors and Staff

Ticks are external parasites that feed on the blood of mammals, birds, reptiles and amphibians, and they can cause a range of illnesses in people and animals. This guide from the National Park Service's health series explains how ticks spread disease and how park visitors, staff and volunteers can protect themselves.

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

How ticks live

Most ticks pass through four life stages: egg, six-legged larva, eight-legged nymph and adult. A tick must take a blood meal to move from one stage to the next, and the full cycle can take up to 3 years. Adults are about 3 to 5 millimeters long — roughly the size of a sesame seed to an apple seed, depending on age, sex, species and how recently they fed — and larvae and nymphs are smaller still.

Infected ticks can pass bacteria, viruses and protozoa to people or animals when they bite and attach. How long a tick must stay attached depends on the germ: the Lyme disease bacterium usually needs more than 36 hours, but other pathogens can be transmitted faster.

Hard ticks and soft ticks

• Hard ticks have a visible shield (scutum) on their backs. They include the black-legged or deer tick (Ixodes scapularis), the lone star tick (Amblyomma americanum) and Dermacentor ticks such as the American dog tick and Rocky Mountain wood tick. They can transmit the germs behind anaplasmosis, babesiosis, ehrlichiosis, Lyme disease, Rocky Mountain spotted fever, tularemia and Powassan virus disease.
• Soft ticks lack a scutum. They can transmit the Borrelia bacteria that cause tickborne relapsing fever.

Ticks cause other problems too. A tick bite can trigger alpha-gal allergy, the so-called "meat allergy," with growing evidence pointing to the lone star tick. And toxins from ticks — most commonly the Rocky Mountain wood tick and American dog tick in the United States — can cause tick paralysis, a rare condition in people and animals that usually goes away once the tick is removed.

In people

Lyme disease is the most common tickborne disease in the United States, with about 400,000 cases a year — a count the NPS notes still underestimates the true burden. Other tickborne diseases are uncommon, with a handful of cases reported each year, and the risk in any area depends on which ticks live there and what they carry.

The most common symptoms are fever, chills, aches and rash. A history, physical exam and laboratory tests can diagnose infection, though tickborne diseases can be hard to recognize. Early detection matters, because many can be treated with antimicrobial drugs. At the time of writing there was no human vaccine for the most common tickborne diseases in the United States, though clinical trials of a new Lyme disease vaccine were under way.

In animals

Rodents are the most common reservoir of tickborne diseases. For some, such as Lyme disease, other wildlife like deer and lizards feed ticks and keep them alive without being infected themselves. Wild birds can carry ticks, including exotic species, and their pathogens, while some animals, such as opossums and squirrels, act as ecological traps that reduce the number of surviving ticks.

Animals suffer from many of the same diseases as people. Some show no signs; others become seriously ill or die, and small animals with heavy infestations can become anemic from blood loss. Oral, topical and wearable tick prevention products are available for dogs, cats and livestock, and most dogs and cats benefit from one. A Lyme disease vaccine for dogs is available and is recommended for dogs that spend time outdoors where Lyme disease is common, in the Northeast and Midwest.

Where ticks live

Hard ticks prefer wooded and brushy areas with tall grass and leaf litter, so in parks they are more likely at the edges of trails or off them. They are found throughout the United States. Soft ticks live in the western half of the country, including Texas, usually at higher elevations (1,500 to 8,000 feet) in the West or in caves and burrows in the South. Over recent decades, climate change is thought to have helped several tick species expand their ranges, and deer management and landscape practices such as fire suppression or controlled burns may also affect tick ecology. Because tickborne disease involves people, wildlife, domestic animals, habitat, climate and social factors together, the NPS calls it a true "One Health" issue.

Prevention

• Find out whether you live, work or are traveling where ticks are a risk.
• Wear protective clothing: long sleeves and pants, pants tucked into socks, and a hat.
• Walk in the center of trails, and avoid brushing against vegetation or sitting on logs.
• Wear light-colored clothes so ticks are easy to spot.
• Use an insect repellent, and treat clothing and gear with permethrin.
• After being outdoors, check your body — especially under the arms, in and around the ears, inside the belly button, behind the knees, in the hair, between the legs and around the waist — as well as clothing, shoelaces, gear and pets.
• Shower soon after being in tick habitat, and tumble clothes on high heat in the dryer for at least 10 minutes to kill ticks.
• Carry a tick kit: repellent such as DEET, 0.5% permethrin for shoes and clothing, tweezers, rubbing alcohol or soap and water, and a mirror for checking yourself.

If you are bitten

• Remove the tick with tweezers, pulling upward with steady pressure. Don't twist it or try to remove it without a tool. Clean the bite well, and consider keeping the tick in a sealed bag or container in case it needs to be identified later.
• See a health care provider if symptoms of tickborne illness appear. Tell them about the bite and when symptoms started, and ask about preventive treatment or other options.
• Park employees should report tick bites to their supervisor and record it as an exposure in SMIS, the reporting system named on the NPS page.

Sources

• National Park Service, Office of Public Health, "Ticks and Tickborne Diseases": https://www.nps.gov/articles/000/ticks-and-tickborne-diseases.htm
• The source spells the lone star tick "lone star stick" in one place.