Transmission of Rickettsia conorii conorii in naturally infected Rhipicephalus sanguineus

Abstract

Rickettsia conorii conorii is the causative agent of Mediterranean spotted fever (MSF) a life-threatening zoonosis that is endemic in Mediterranean countries [1]. In the early 1930s, Olmer supposed that the vector of disease was the brown dog tick, Rhipicephalus sanguineus. In 1932, Blanc and Caminopetros demonstrated that larvae, nymphs, adults, and over winter unfed males and females could act as vectors of MSF [2]. It was also shown that when eggs or larvae obtained from infected Rh. sanguineus females, were crushed and used to inoculate humans, the patients contracted MSF. These data suggest that transovarial transmission of the MSF agent occurs in ticks. However, we are unaware of any well-documented demonstration of transovarial transmission rate of R. conorii in Rh. sanguineus (TOT, the proportion of infected females giving rise to at least one positive egg or larva), or the filial infection rate (FIR, proportion of infected eggs or larvae obtained from an infected female). Although it is not known, infection with R. conorii is maintained over several generations of Rh. sanguineus. Furthermore, a high mortality of Rh. sanguineus group ticks infected with R. conorii by several methods has been recently reported [3,4]. Our aim was to examine the vertical transmission of R. conorii in naturally infected Rh. sanguineus ticks, to establish a colony of infected ticks and to study the maintenance of infection through several generations. MATERIAL AND METHODS