Molecular detection and characterization of rickettsia species in rodents and shrews from Kilombero district, Tanzania

Background: Rickettsia is a genus of obligatory intracellular bacteria transmitted by arthropods such as lice, ticks, and fleas. Rodents and shrews are well known for harboring a plethora of zoonotic pathogens including rickettsia. The diseases associated with Rickettsia are often misdiagnosed with other febrile infections such as Malaria and typhoid fever. This study aimed to detect and characterize the prevailing Rickettsia species in rodents and shrews from Kilombero district, Tanzania. Methods: This study was conducted in Kilombero district between June 2022 and March 2023. The rodents and shrews were captured inside the households and outside households or in farms in the selected areas baited with maize bran and peanut butter. Prior to identification, rodents and shrews were anaesthetized by using Halothane was administered at the dose of 2mg/kg. DNA extraction from 204 tissue samples was done using DNeasy Blood and Tissue Kit from Qiagen. Amplification of the Citrate synthase (gltA) gene was done by Nested PCR using two sets of primer sequences in both rounds. PCR products were sequenced twice in the forward and reverse directions, consensus sequences were created and BLAST analysis was done. A phylogenetic tree was constructed using the Neighbor-Joining Method and 1000 bootstrap replications using the same software. The relationship between rodents’ rickettsiosis status to different factors were analyzed using chi-squared test. Results: The overall molecular prevalence of Rickettsia species in rodents and shrews was: 10.20% (95% CI: 0.0634-0.153; n/N=20/196) and 12.5% (95%: CI: 0.0032-0.5265; n/N=1/8) respectively. Upon sequencing, all sequences were identified as Rickettsia conorii subsp. raoultii with percentage identity ranging from 98% to 100%. Conclusion: This study confirms that rodents and shrews are infected with Rickettsia conorii in the study area.