Molecular detection of spotted fever group rickettsiae in ticks from Cameroon

In western and eastern Africa, rickettsioses are one cause of fever in humans. Little is known regarding the presence of Rickettsia sp. in northern Cameroon. The present work was conducted in order to identify potential tick-borne spotted fever group Rickettsia in the Adamawa region of northern Cameroon, which may contribute filling some of the knowledge gaps of these pathogens. Ticks were collected from cattle in the municipal slaughterhouse of Ngaoundere in the Adamawa region of northern Cameroon. After morphological identification of tick species, extracted DNA was analyzed by PCR targeting the rickettsial ompB gene and the intergenic spacers dksA-xerC, mppA-purC and rpmE-tRNA^fMet_. Of the 316 adult ticks collected, 149 (47.1%) were Amblyomma variegatum, 92 (29%) Rhipicephalus spp. and 75 (23.7%) Hyalomma spp. Through the use of conventional PCR assays for the rickettsial ompB gene, rickettsial DNA was detected in 104 (32.9%) samples (85 Amblyomma sp., 14 Hyalomma spp. and 5 Rhipicephalus spp.). The ompB gene and the three intergenic were sequenced for 10 ticks in order to determine the rickettsial species. Rickettsia africae was detected in Amblyomma variegatum, Rickettsia aeschlimannii in Hyalomma rufipes and Hyalomma truncatum, Rickettsia sibirica in H. truncatum, Rickettsia massiliae in Rhipicephalus lunulatus and Candidatus Rickettsia barbariae in R. lunulatus. To the best of the author's knowledge, this report represents the first molecular evidence of rickettsial infection in ticks in the Adamawa region of northern Cameroon, which suggests a possible exposure of the human population in this region.