Lyme disease is a significant public health concern in the United States, with Pennsylvania consistently reporting a high number of cases annually. It is primarily transmitted to humans through the bite of infected blacklegged ticks, also known as deer ticks. This article provides information on tick infection rates in Pennsylvania, factors influencing these rates, the transmission process, and strategies for minimizing exposure.
Prevalence of Infected Ticks in Pennsylvania
The blacklegged tick (Ixodes scapularis), the primary vector for Lyme disease, is found in all 67 counties of Pennsylvania. Recent surveillance data indicates a notable percentage of these ticks carry Borrelia burgdorferi, the bacterium responsible for Lyme disease. For instance, a comprehensive analysis by the PA Tick Research Lab, which tested over 65,000 ticks from 2019 to 2021, revealed that 29% were infected. In southwestern Pennsylvania, nearly 28.8% of nymphal blacklegged ticks tested positive for B. burgdorferi, while statewide data from 2022-2023 indicates an infection rate of 59.5% for adult ticks. Across the broader Northeastern United States, adult blacklegged ticks can have infection rates as high as 50%, and nymphs up to 25%.
Factors Affecting Tick Infection Rates
Tick infection rates in Pennsylvania are influenced by geographical, seasonal, and environmental factors. Geographical variations exist, with higher prevalence in some rural and urban areas. Ticks are commonly found in wooded and brushy areas, high grass, and leaf litter, including urban parks and backyards where host animals like mice, birds, or deer are present. Ticks are most active from April through September, with nymphal blacklegged ticks peaking in late spring and early summer, correlating with the highest incidence of human Lyme disease cases. Environmental changes, such as land use shifts and a warming climate, contribute to expanding tick populations and range, aided by the abundance of host animals like white-footed mice and deer, which provide blood meals and aid in bacterial circulation.
Lyme Disease Transmission Process
Lyme disease is transmitted when an infected blacklegged tick bites a human. The bacteria, Borrelia burgdorferi, are typically located in the tick’s midgut. For transmission to occur, the bacteria must migrate from the midgut to the tick’s salivary glands during the feeding process, which generally requires a period of sustained attachment. While it is commonly stated that transmission often occurs after 36 to 72 hours of tick attachment, some research suggests that transmission can happen in less than 24 hours, with risk increasing with the duration of tick attachment. Blacklegged ticks undergo a three-stage life cycle—larva, nymph, and adult—each requiring a blood meal, acquiring bacteria from infected wildlife and transmitting it during subsequent feedings; nymphs are particularly significant due to their small size.
Minimizing Exposure to Ticks
To minimize exposure to ticks in Pennsylvania, take precautions. When outdoors, especially in wooded or brushy areas with tall grass and leaf litter, stay in the center of trails to avoid direct contact with vegetation. Use EPA-registered insect repellents on exposed skin (e.g., DEET, picaridin, oil of lemon eucalyptus) and treat clothing with 0.5% permethrin. Wear light-colored clothing, tucking pants into socks and shirts into pants, and conduct a thorough tick check on your entire body after outdoor activities, including areas like armpits, behind the knees, and hairline. Showering within two hours of coming indoors and placing clothes directly into a hot dryer can further reduce risk.