Tick-bite fever in South Africa. The occurrence of severe cases on the Witwatersrand.

Tick-bite fever, the variety of tick typhus occurring in southern Africa, is caused by Rickettsia conori var. pijperi and is transmitted by hard or ixodid ticks. It is usually a mild disease, especially in children and young adults, but in middle-aged and elderly patients (and sometimes in young adults) it may assume a severe form. This is characterized by high fever, severe headache, delirium, stupor and occasionally coma, and a profuse maculopapular rash which becomes haemorrhagic and is associated with petechiae in the skin and later, but rarely, by the development of gangrene of the fingers and toes. During these severe attacks the central nervous system may be involved and marked disorders of liver and kidney function sometimes lead to kidney failure and the need for treatment and dialysis in an intensive care unit. Three illustrative cases are described in which diagnosis was delayed. One patient died; 2 patients responded to administration of tetracycline. The danger of allowing tick-infested dogs onto one's bed is stressed. Infections transmitted by dog ticks tend to be more severe than those acquired via ticks from the bushveld, possibly because they so often occur in middle-aged and elderly patients. Serological tests have recently indicated that there are antigenic differences between 'suburban' and 'bushveld' strains; these clearly require further study.