부산대학교 도서관

Tick-borne spotted fever group (SFG) rickettsioses are emerging infectious diseases in Sub-Saharan Africa. In Madagascar, the endemicity of tick-borne rickettsiae and their vectors has been incompletely studied. The first part of the present study was conducted in 2011 and 2012 to identify potential anthropophilic tick vectors for SFG rickettsiae on cattle from seven Malagasy regions, and to detect and characterize rickettsiae in these ticks. Amblyomma variegatumwas the only anthropophilic tick species found on 262 cattle. Using a novel ompB-specific qPCR, screening for rickettsial DNA was performed on 111 A. variegatumticks. Rickettsial DNA was detected in 96 of 111 ticks studied (86.5%). Rickettsia africaewas identified as the only infecting rickettsia using phylogenetic analysis of ompAand ompBgene sequences and three variable intergenic spacers from 11 ticks. The second part of the study was a cross-sectional survey for antibodies against SFG rickettsiae in plasma samples taken from healthy, pregnant women at six locations in Madagascar, two at sea level and four between 450 and 1300m altitude. An indirect fluorescent antibody test with Rickettsia conoriias surrogate SFG rickettsial antigen was used. We found R. conorii-seropositives at all altitudes with prevalences between 0.5% and 3.1%. Our results suggest that A. variegatumticks highly infected with R. africaeare the most prevalent cattle-associated tick vectors for SFG rickettsiosis in Madagascar. Transmission of SFG rickettsiosis to humans occurs at different altitudes in Madagascar and should be considered as a relevant cause of febrile diseases.