Molecular characteristics of Neoehrlichia mikurensis carried by rodents in Guangzhou, Guangdong

  Objective   To analyze the molecular characteristics of Neoehrlichia mikurensis isolated from rodents in Guangzhou, Guangdong province.

  Methods  Rodents were captured by night trapping and caging methods in 9 districts in Guangzhou, the spleens of rodents captured were dissected, and nested polymerase chain reaction (PCR) was applied to amplify the fragments of the 16S rRNA and groEL genes of N. mikurensis. In addition, the positive PCR products were sequenced and phylogenetic analysis was performed by using the corresponding sequences from GenBank.

  Results   In 1104 rodent samples, 29 were tested to be positive for N. mikurensis, the overall positive rate was 2.63%. The positive rate was 0.39% (2/510) in 2019, 0.98% (3/307) in 2020, and 8.36% (24/287) in 2021, the differences were significant. The positive rodents were mainly detected in Conghua (9.00%), Zengcheng (3.23%) and Baiyun districts (0.86%). In six rodent species collected, Rattus flavipectus had the highest positive rate (7.69%), followed by Rattus norvegicus (2.87%) and Rattus losea (1.11%). The sequences of the groEL and 16S rRNA genes of N. mikurensis in Guangzhou were highly homologous, belonging to Cluster Ⅳ clade.

  Conclusion   N. mikurensis strains, with high homologous gene sequences, have been detected in rodents in Guangzhou with the high detection rate in some districts, indicating a potential risk for N. mikurensis infection outbreak. It is necessary to strengthen the molecular epidemiology surveillance for N. mikurensis in Guangzhou.