Lyme disease, often associated with the Eastern United States, is a concern for outdoor enthusiasts. While its prevalence in Oregon differs from other regions, it is indeed present. Understanding its local dynamics is important for residents and visitors.
Lyme Disease in Oregon
Lyme disease is found throughout Oregon, though its incidence is considerably lower than in the eastern and midwestern United States. Cases are reported annually, with an average of about 69 human cases each year over the past six years. In 2022, 65 cases were reported.
The risk of acquiring Lyme disease in Oregon is highest in the southwestern region, especially in counties like Coos, Curry, Josephine, and Jackson, due to higher tick density. While cases occur statewide, including the Portland area, locally acquired infection rates may be lower in urban areas compared to rural, tick-dense regions.
How Lyme Disease is Transmitted
Lyme disease is caused by Borrelia burgdorferi bacteria, transmitted to humans through infected tick bites. In Oregon and the western United States, the primary vector is the western blacklegged tick (Ixodes pacificus), unlike the Eastern US where Ixodes scapularis (deer tick) is the main vector.
Ticks become infected by feeding on small animals carrying the bacteria, such as rodents and birds. For transmission to occur, an infected tick typically needs to be attached for at least 24 to 48 hours. Prompt removal of ticks greatly reduces the risk of infection.
Identifying Symptoms
Recognizing Lyme disease symptoms is important for early diagnosis and treatment. The most characteristic early sign is erythema migrans, a circular or oval rash often described as a “bull’s-eye” appearance, occurring in about 70-80% of cases. This rash typically appears 3 to 30 days after a tick bite and can expand over several days or weeks. However, not everyone develops or notices this rash.
Other early symptoms, which may resemble the flu, include fever, chills, headache, fatigue, and muscle and joint aches. If left untreated, the infection can spread, leading to more severe symptoms weeks or months later. These can involve joint pain and swelling (Lyme arthritis, often affecting the knees), neurological issues like facial palsy or nerve pain, and, less commonly, heart problems.
Preventing Lyme Disease
Preventing tick bites is the most effective way to avoid Lyme disease. When in wooded or grassy areas, especially from spring through fall when ticks are most active, wear long pants and sleeves, tucking pant legs into socks. Wearing light-colored clothing can also make it easier to spot ticks.
Using insect repellents containing 20-30% DEET or picaridin on exposed skin can deter ticks. Treating clothing and gear with permethrin is another effective measure, though permethrin should not be applied directly to the skin.
After spending time outdoors, perform a thorough tick check on yourself, children, and pets, focusing on areas like armpits, groin, and hair. Showering within two hours of coming indoors may also help wash off unattached ticks.
If a tick is found, remove it promptly using fine-tipped tweezers by grasping it close to the skin and pulling upward with steady, even pressure, avoiding twisting or squeezing. Clean the bite area with soap and water after removal.