Tick bite fever in southern Africa

Abstract

Tick bite fever (TBF) is a well-known zoonotic disease in southern Africa, caused by ixodid tick-transmitted rickettsial pathogens of the spotted fever group, which target endothelial cells, producing widespread vasculitis. Two epidemiologic and clinical forms of the condition can be distinguished, namely, African TBF and Mediterranean spotted fever–like infection. TBF is generally a mild illness, but delayed diagnosis and inappropriate treatment may lead to severe, potentially fatal, disease resembling bacterial sepsis, viral hemorrhagic fever, malaria, or other serious infections. Along with compatible epidemiologic history, common clinical diagnostic features at initial presentation are fever, headache, rash, myalgia and eschar; tender regional lymphadenopathy is common. Clinical diagnosis is sufficient to warrant treatment because serological response is slow to develop; although polymerase chain reaction of eschar material is an additional or alternative diagnostic option, this method may not be readily available. The treatment of choice is doxycycline, with macrolides as second-line antibiotics. Personal prevention revolves around awareness of risks and measures to limit exposure to ticks. As a zoonosis with a wide range of reservoir hosts, the disease cannot be eliminated but risk can be reduced by application of One Health principles.

HIGHLIGHTS • Tick bite fever (TBF) is a common regional tick-transmitted rickettsial infection. • Two forms: Mediterranean spotted fever (MSF)–like and African tick bite fever (ATBF). • MSF and ATBF differ in pathogen and vector species, epidemiology, and severity. • Severe TBF can resemble other bacterial sepsis or viral hemorrhagic fever. • The antibiotic of first choice is doxycycline in most patients; alternatively, macrolides.