Role of cattle in the epidemiology of tick-bite fever in Zimbabwe.

Almost 100% of 52 cattle tested from the southern areas of Zimbabwe were found to have antibodies reactive with Rickettsia conorii compared with less than 30% of 120 cattle from the north. Steers artificially infected with R. conorii isolated from Amblyomma hebraeum were found to show no hematological or biochemical signs of disease but did seroconvert. Clinical signs of infection were restricted to regional lymphadenopathy and dermal erythema, edema, and tenderness at the inoculation site. Rickettsemia was detectable for at least 32 days postinfection. Our findings indicate that cattle could be involved in the transmission of rickettsias by A. hebraeum and may serve as a reservoir of human tick-bite fever in southern Africa.