Relapsing Fever
Two to 15 days following infection, patients have an abrupt onset of fever, headache, and myalgia that lasts for 4 to 10 days. Physical findings often include petechiae, diffuse abdominal tenderness, and conjunctival effusion. As the host produces specific antibody in response to the agent, organisms disappear from the bloodstream, becoming sequestered (hidden) in different organs during the afebrile period. Subsequently, organisms reemerge with newly modified antigens and multiply, resulting in another febrile period. Subsequent relapses are usually milder and of shorter duration. Generally, more relapses are associated with cases of untreated tickborne relapsing fever, but louseborne relapsing fevers tend to be more severe.
Treatment of relapsing fever with antibiotics may result in the formation of the Jarisch-Herxheimer reaction. This reaction is associated with the clearance of the organisms from the bloodstream and release of cytokines within hours of antibiotic treatment. The patient experiences tachycardia, chills, rigors, hypotension, fever, and diaphoresis. Death may be associated with the reaction. An acute respiratory distress syndrome has also been recognized in cases associated with tickborne relapsing fever.
Lyme Disease
Lyme disease is characterized by three stages, not all of which occur in any given patient. The first stage, erythema migrans (EM), is the characteristic red, ring shaped skin lesion with a central clearing that first appears at the site of the tick bite but may develop at distant sites as well (Figure 1). Patients may experience headache, fever, muscle and joint pain, and malaise during this stage. The second stage, beginning weeks to months after infection, may include arthritis, but the most important features are neurologic disorders (i.e., meningitis, neurologic deficits) and carditis. This is a result of the hematogenous spread of spirochetes to organs and tissues. In addition, neurologic symptoms and infection may occur in the meninges, spinal cord, peripheral nerves, and brain. The third stage is usually characterized by chronic arthritis or acrodermatitis chronica atrophicans (ACA), a diffuse skin rash, and may continue for years. There is an association between Borrelia species and distinct clinical manifestations. For example, B. garinii has been associated with up to 72% of European cases of neuroborreliosis.
Fig1. Appearance of the classic erythema migrans lesion of acute Lyme disease.
