Background:The genus Rickettsia in the order Rickettsiales(Alphaproteobacteria)consists of gram-negative obligate intracellular bacteria that infect a wide range of hosts.Epidemiological studies on the occurrence of R...Background:The genus Rickettsia in the order Rickettsiales(Alphaproteobacteria)consists of gram-negative obligate intracellular bacteria that infect a wide range of hosts.Epidemiological studies on the occurrence of Rickettsia spp.and their associated tick vectors are essential to understand their distribution,host range,and transmission mechanisms in nature.This is particularly relevant within the One Health framework,which emphasizes the interconnectedness of animal,human,and environmental health.Methods:To investigate the presence of Rickettsia spp.in dogs and their ticks in Malawi,a molecular survey was conducted.A total of 209 dog blood and 259 tick samples of the species Haemaphysalis elliptica(n=16)and Rhipicephalus linnaei(n=243)were screened using real-time quantitative PCR(qPCR)targeting the citrate synthase(gltA)gene.Positive samples were further characterized via the conventional PCR and Sanger sequencing of gltA and the outer membrane protein A(ompA)genes.Results:Rickettsia DNA was not detected in any dog samples.However,the detection rates in R.linnaei and H.elliptica were 2.5%(n=6)and 6.3%(n=1),respectively.The obtained sequences showed 100% identity with Rickettsia conorii subsp.conorii(n=4),99%-100% with Rickettsia massiliae(n=2),and 100% with Rickettsia rhipicephali(n=1).Phylogenetic analysis clustered these sequences with the corresponding sequences of R.conorii subsp.conorii,R.massiliae,and R.rhipicephali reported from other countries in both gltA and ompA gene-based phylogenetic trees.The detection of R.massiliae and R.rhipicephali in southern Africa suggests expansion of the geographical distribution of these potentially zoonotic Rickettsia species.Conclusion:This is the first report of Rickettsia species detection in ticks collected from dogs in Malawi.The findings highlight the need for further surveillance,including humans and other animals,to better assess the public and veterinary health risks.Public engagement is needed to raise awareness on the role of dogs and their ticks in the transmission of Rickettsia within the One Health approach.展开更多
基金supported in part by the Japan Society for the Promotion of Science(JSPS)KAKENHI(grant numbers JP23K23770,JP24KK0133,and JP25K02166)the Japan Agency for Medical Research and Developmen(AMED)(grant numbers JP18jm0510001 and JP23wm0225034)JST SPRING(grant number JPMJSP2119).
文摘Background:The genus Rickettsia in the order Rickettsiales(Alphaproteobacteria)consists of gram-negative obligate intracellular bacteria that infect a wide range of hosts.Epidemiological studies on the occurrence of Rickettsia spp.and their associated tick vectors are essential to understand their distribution,host range,and transmission mechanisms in nature.This is particularly relevant within the One Health framework,which emphasizes the interconnectedness of animal,human,and environmental health.Methods:To investigate the presence of Rickettsia spp.in dogs and their ticks in Malawi,a molecular survey was conducted.A total of 209 dog blood and 259 tick samples of the species Haemaphysalis elliptica(n=16)and Rhipicephalus linnaei(n=243)were screened using real-time quantitative PCR(qPCR)targeting the citrate synthase(gltA)gene.Positive samples were further characterized via the conventional PCR and Sanger sequencing of gltA and the outer membrane protein A(ompA)genes.Results:Rickettsia DNA was not detected in any dog samples.However,the detection rates in R.linnaei and H.elliptica were 2.5%(n=6)and 6.3%(n=1),respectively.The obtained sequences showed 100% identity with Rickettsia conorii subsp.conorii(n=4),99%-100% with Rickettsia massiliae(n=2),and 100% with Rickettsia rhipicephali(n=1).Phylogenetic analysis clustered these sequences with the corresponding sequences of R.conorii subsp.conorii,R.massiliae,and R.rhipicephali reported from other countries in both gltA and ompA gene-based phylogenetic trees.The detection of R.massiliae and R.rhipicephali in southern Africa suggests expansion of the geographical distribution of these potentially zoonotic Rickettsia species.Conclusion:This is the first report of Rickettsia species detection in ticks collected from dogs in Malawi.The findings highlight the need for further surveillance,including humans and other animals,to better assess the public and veterinary health risks.Public engagement is needed to raise awareness on the role of dogs and their ticks in the transmission of Rickettsia within the One Health approach.
