Molecular detection of multiple Rickettsia species in ticks from the Republic of Guinea

Tick-borne rickettsioses are emerging and re-emerging zoonotic diseases worldwide that are caused by Gram-negative bacteria of the genus Rickettsia. Ticks act as both reservoirs and vectors for these bacteria, thereby increasing opportunities for the spillover of infections that they cause. This study aims to bridge the knowledge gap regarding the occurrence of zoonotic Rickettsia species in the Republic of Guinea. Ticks were manually collected from dogs, cattle, goats, and sheep. Morphological identification of 1213 ixodid ticks revealed five genera. Screening of individual DNA for Rickettsia spp. showed a prevalence of 39% (469/1213; 95% CI [36%-41%]). The main tick genera positive for Rickettsia spp. were Amblyomma spp. 83.7% (300/358), Rhipicephalus spp. 22% (165/744), Hyalomma spp. 7.3% (3/41), and Haemaphysalis spp. 3% (2/69). Molecular analysis of positive tick genera confirmed nine species. Subsequent specific qPCR assays and sequencing identified five Rickettsia species, including Rickettsia africae (36%), Rickettsia aeschlimannii (0.5%), Rickettsia massiliae (1%), Rickettsia conorii (0.2%), and a new genotype named Rickettsia sp. "guineensis" (0.1%). Additionally, two strains of Rickettsia africae were isolated from Amblyomma variegatum by cell culture techniques using XTC-2 cells and S2 cells. The present study highlights the need for further surveillance involving humans and other animals to better assess the public and veterinary health risks posed by zoonotic Rickettsia species.