Borrelia afzelii is a significant cause of Lyme disease (Lyme borreliosis) in Europe and parts of Asia. It is a spiral-shaped bacterium called a spirochete. It is a member of the Borrelia burgdorferi sensu lato complex, which includes several closely related species capable of causing Lyme disease. This complex of bacteria is responsible for the most common vector-borne illness in temperate regions globally.
What is Borrelia afzelii
Borrelia afzelii is one of the primary genospecies within the Borrelia burgdorferi sensu lato complex responsible for Lyme borreliosis in Eurasia. It is classified as a spirochete, characterized by its loosely coiled, spiral shape. They possess internal flagella that enable their motility.
While Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in North America, Borrelia afzelii is the predominant species in Europe and parts of Asia, alongside Borrelia garinii. Each genospecies is often associated with different clinical manifestations; B. afzelii is primarily linked to skin issues. It is a tick-borne bacterium widespread in European ticks.
How Borrelia afzelii is Transmitted
Borrelia afzelii is primarily transmitted through the bite of infected ticks. In Europe, the main vector is the castor bean tick, Ixodes ricinus. Ticks become infected when they feed on animals that carry the bacterium, such as rodents and birds.
The transmission risk increases with the length of time a tick is attached, typically over 24 hours, as the bacteria move from the tick’s gut to its salivary glands and then into the host. Tick nymphs, which are immature ticks, are often responsible for human infections due to their small size, making their bites less noticeable. Borrelia afzelii spirochetes can be present in the skin of a host within one day of tick attachment, and most infections can be established within 48 hours.
Symptoms of Borrelia afzelii Infection
Infection with Borrelia afzelii commonly presents with distinct skin manifestations. The earliest and most frequent sign is erythema migrans (EM), which occurs in approximately 60-80% of infected individuals. This characteristic “bull’s-eye” rash typically appears at the tick bite site within 3 to 30 days, expanding outwards and often clearing in the center. The rash is usually not significantly raised or painful and can be accompanied by general symptoms like fatigue, headache, and muscle aches.
Acrodermatitis chronica atrophicans (ACA) is a late-stage skin manifestation particularly associated with B. afzelii. This condition begins with bluish-red discoloration and swelling, typically on the extremities like hands and feet, leading to skin thinning and atrophy over time. Another less common localized skin lesion is borrelial lymphocytoma, which appears as a small, bluish-red nodule, often on the earlobe, nipple, or scrotum.
Diagnosis and Treatment Approaches
Diagnosis of Borrelia afzelii infection often begins with a clinical assessment of symptoms, especially erythema migrans, alongside a history of potential tick exposure. Laboratory tests, such as enzyme-linked immunosorbent assay (ELISA) and Western blot, can support the diagnosis by detecting antibodies. However, these tests may show false negatives in the early stages of infection, as antibody levels might not yet be detectable, and antibodies can persist even after successful treatment.
Antibiotic therapy is the standard treatment for Borrelia afzelii infection. Common oral antibiotics include doxycycline, amoxicillin, and cefuroxime. For more complicated or late-stage manifestations, intravenous antibiotics such as ceftriaxone may be prescribed. The specific antibiotic and treatment duration, typically a few weeks, depend on the infection’s stage and severity. Early treatment is important to prevent the progression to more chronic manifestations.
Preventing Borrelia afzelii Infection
Preventing Borrelia afzelii infection primarily involves avoiding tick bites. When in tick-prone areas like tall grass or dense brush, wearing protective clothing like long-sleeved shirts and long pants can reduce exposure. Using insect repellents containing active ingredients like DEET or picaridin on exposed skin and clothing also provides a barrier against ticks.
After spending time outdoors, perform thorough tick checks on your body, clothing, and pets. If a tick is found attached, remove it promptly using fine-tipped tweezers, grasping the tick as close to the skin surface as possible and pulling upward with steady, even pressure. Avoiding direct contact with high-risk vegetation helps minimize the chance of encountering infected ticks.