Borrelioses

Borrelioses are diseases caused by spirochete bacteria of the genus Borrelia. The best known forms are Lyme borreliosis (Lyme disease) and relapsing fever borrelioses. Transmission to humans occurs mainly through ticks; in epidemic relapsing fever, body lice or soft ticks can serve as vectors.

Causative agents include Borrelia burgdorferi sensu lato, a group of species causing Lyme borreliosis in the Americas, Europe, and Asia. Other species, such as B. recurrentis, B. duttonii, and B. crocidurae, cause relapsing fever and are transmitted by soft ticks or body lice.

Clinical features vary by syndrome. Lyme borreliosis often begins with erythema migrans, an expanding skin lesion, accompanied by fever or fatigue. If untreated, dissemination can occur, with multiple skin lesions, facial palsy, meningitis, carditis, and later arthritis, especially of the knee.

Relapsing fever borrelioses present with recurrent febrile episodes separated by afebrile intervals. Severe disease may involve the CNS, liver, or spleen. Diagnosis relies on identification of spirochetes in blood during febrile episodes for relapsing fever; Lyme borreliosis is typically diagnosed with serology and, when needed, PCR.

Treatment uses antibiotics chosen by syndrome and stage. Early Lyme disease is commonly treated with doxycycline or amoxicillin; neurologic or cardiac involvement may require intravenous ceftriaxone. Relapsing fever is treated with tetracyclines or penicillin, usually for short courses with rapid improvement.

Prevention focuses on tick avoidance and prompt removal, use of repellents, protective clothing, and avoiding tick-infested areas. Public health monitoring helps track incidence and vector distribution.