Lyme disease is a bacterial infection transmitted to humans through the bite of an infected tick. The bacterium responsible for this illness, Borrelia burgdorferi, is carried exclusively by one specific species in the region. The Blacklegged Tick, scientifically known as Ixodes scapularis, is the sole vector of the Lyme disease pathogen within the state.
Identifying the Blacklegged Tick
The Blacklegged Tick is found throughout Pennsylvania in wooded, brushy, and grassy-edged habitats where it actively seeks hosts. The adult female is the largest and most easily recognized, featuring a reddish-orange body combined with a distinct black dorsal shield, or scutum.
Adult males appear entirely dark brown or black because their scutum covers most of their body. Adults are most active in the cooler months of the fall and spring, often found questing on low-lying vegetation to latch onto passing hosts.
The nymph stage is responsible for the majority of human infections. Nymphs are active primarily during the late spring and summer months, making them difficult to spot on the skin.
Nymphs must feed on an infected host, such as a white-footed mouse, to acquire the Borrelia burgdorferi bacteria before they can transmit it to a human. The tick must be attached for 36 to 48 hours for the bacteria to successfully pass from the tick’s gut into the host’s bloodstream.
Other Common Ticks in Pennsylvania
Pennsylvania is home to several other common tick species that may transmit different pathogens. The American Dog Tick, Dermacentor variabilis, is one of the most frequently encountered species and is substantially larger than the Blacklegged Tick. This tick has a distinctive mottled brown and white pattern on its back and prefers open, grassy fields and scrublands rather than dense woods.
The American Dog Tick transmits the bacteria that causes Rocky Mountain Spotted Fever. A third species of concern is the Lone Star Tick, Amblyomma americanum, which is becoming more prevalent in the state’s southern counties.
The adult female Lone Star Tick is easily identified by a prominent, solitary white or silver spot on her back. Although it does not transmit Lyme disease, the Lone Star Tick can transmit pathogens causing ehrlichiosis and Southern Tick-Associated Rash Illness (STARI). Bites from this species are also linked to Alpha-gal syndrome, a condition that can cause an allergic reaction to red meat.
Immediate Action Following a Tick Bite
If a tick is found attached to the skin, use a pair of clean, fine-tipped tweezers to grasp the tick as close to the skin’s surface as possible. Pull upward with a steady, even pressure, avoiding twisting or jerking movements that might cause the mouthparts to break off in the skin.
After the tick is successfully removed, thoroughly clean the bite site and your hands using rubbing alcohol or soap and water. Folklore remedies, such as coating the tick with petroleum jelly or using heat, should be avoided as they may cause the tick to regurgitate its stomach contents, potentially increasing the risk of disease transmission.
Watch for the appearance of a characteristic expanding red rash, which is a symptom of early Lyme disease. Other symptoms that warrant a call to a healthcare provider include fever, fatigue, or joint pain appearing within 30 days of the bite. Physicians may consider a single-dose prophylactic antibiotic treatment if the attached tick is identified as a Blacklegged Tick and is estimated to have been attached for longer than 36 hours.