Ticks are small arachnids that feed on blood, and their presence is a consideration for anyone spending time outdoors in Washington State. Understanding the types of ticks present and the potential health concerns they pose can help individuals navigate outdoor environments more safely. Knowing where ticks reside and how to reduce exposure are practical steps for mitigating risks.
Common Tick Species in Washington State
Washington State is home to several tick species, each with distinct characteristics and habitats. The Western Black-legged tick (Ixodes pacificus) is found in western Washington and along the eastern slopes of the Cascade Mountains, preferring forested or brushy environments. These ticks are brownish-black, with nymphs appearing as small as a freckle.
The Rocky Mountain Wood tick (Dermacentor americanus) is prevalent in eastern Washington, residing in woodlands and grassy shrubs. These reddish-brown ticks are larger than the Western Black-legged tick. The Western Dog tick (Dermacentor similis) is robust and reddish-brown with grayish markings, inhabiting woodlands and grassy areas in the eastern and southwestern parts of the state, often in sunny, open spaces at the edges of woods. Soft ticks, such as Ornithodoros hermsi, lack a hard outer shell, feed briefly at night, and are often encountered in mountainous regions within rodent burrows or nests, making their bites often unnoticeable.
Diseases Associated with Ticks
Ticks in Washington State can transmit several diseases, though the number of cases reported annually is generally lower compared to some other U.S. regions. Anaplasmosis, caused by the bacterium Anaplasma phagocytophilum, is primarily transmitted by the Western Black-legged tick. Symptoms, which can include chills, fever, severe headache, muscle aches, nausea, vomiting, or diarrhea, typically appear one to two weeks after a bite. Washington reported its first locally acquired human case of anaplasmosis in 2022.
Lyme disease, caused by the bacterium Borrelia burgdorferi, is also transmitted by the Western Black-legged tick. Although rare, cases do occur in Washington, and symptoms can include an expanding circular rash, often described as a “bullseye,” along with fever, chills, joint pain, and fatigue.
Rocky Mountain Spotted Fever (RMSF) is caused by bacteria from the Rickettsia genus and is transmitted by the American Dog tick and the Rocky Mountain Wood tick. Initial symptoms may include fever, headache, rash, and muscle aches. Tick-borne relapsing fever is transmitted by soft ticks, particularly Ornithodoros hermsi, and is characterized by recurrent episodes of fever, often linked to exposure in rustic, rodent-infested cabins.
Tick paralysis, a rare condition, results from a neurotoxin in tick saliva, often from the Rocky Mountain Wood tick. This condition can lead to progressive paralysis that typically starts in the legs and moves upward, potentially affecting respiratory muscles, but prompt tick removal usually leads to complete recovery. Tularemia, which can be transmitted by the American Dog tick or the Rocky Mountain Wood tick, may cause sudden fever, headache, swollen lymph nodes, and a skin ulcer near the bite. Babesiosis, caused by Babesia parasites and potentially transmitted by the Western Black-legged tick, can result in chills, fatigue, fever, muscle pain, and anemia, with a small number of cases reported in Washington.
Areas of Concern in Washington
Ticks are present throughout Washington State, from dense forests and coastal regions to urban parks and backyards. Their populations are particularly notable in areas with significant deer populations, which serve as primary hosts for adult ticks. Specific locations of concern include the Kitsap Peninsula, Pierce, Jefferson, Snohomish, Skagit, and King counties, as well as areas in southern Washington around Longview.
Ticks thrive in environments with tall grass, brush, and leaf litter, making wooded areas, hiking trails, and the edges of forests common places for encounters. While ticks can be found year-round, their activity generally peaks during the warmer months of spring and early summer. This seasonal increase in activity aligns with greater human outdoor engagement, raising the potential for tick exposure.
Minimizing Tick Exposure
When spending time outdoors in tick habitats, wearing appropriate clothing can provide a physical barrier. Light-colored, tightly woven long pants and long-sleeved shirts are recommended, with pant legs tucked into socks or boots and shirts tucked into pants to keep ticks on the outside of clothing where they are more easily spotted. Treating clothing and gear with permethrin, an insecticide, can also be effective, while EPA-registered insect repellents containing DEET can be applied to exposed skin.
After outdoor activities, conducting a thorough tick check is advisable. Showering within two hours of returning indoors can help wash off unattached ticks and is a good opportunity to inspect the body, paying close attention to areas like the hair, ears, underarms, belly button, waist, between the legs, and behind the knees.
For tick removal, fine-tipped tweezers should be used to grasp the tick as close to the skin’s surface as possible, pulling upward with steady, even pressure. The bite area should then be cleaned with soap and water or rubbing alcohol. If a rash, fever, or flu-like symptoms develop within several weeks of a tick bite, seeking medical attention is recommended.