Abstract:

Objective To investigate the infectious status of Babesia spp. in hosts and vectors in the central and south areas of Zhejiang Province, and analyze the 18S rRNA gene sequence from a patient confirmed to have human babesiosis in Zhejiang Province and align it with that in GenBank, in order to understand the genetic relationship and evolutionary characteristics of Babesia. Methods Anticogulated blood was collected from animal hosts and Babesia spp. vectors were collected. DNA was extracted from these samples and PCR was performed to amplify the 18S rRNA gene of Babesia. The PCR products were further sequenced and sequence alignment was performed to identify the species of Babesia. The family- and species-specific 18S rRNA sequences of Babesia spp., as well as those of B. microti from different animal hosts and from different geographical source regions were searched in the NCBI database and analyzed by BLAST. Phylogenetic trees were constructed by the MEGA5 software. Results Thirty-seven samples from a total of 261 produced positive bands. The positive rate of anticogulated blood from animal hosts was 14.2% (32/225), and that of vectors was 13.9%(5/36). The positive bands were sequenced, and 20 underwent successful sequencing. Results of sequence alignment revealed five samples with B. microti infection from rodents, four samples with Sarcocystis sp. infection, two with Hepatozoon sp. infection, one with Coccidia sp. infection, five with Theileria orientalis infection, two with T. buffeli infection and one B. caballi infection in rodent and cattle hosts/vetors. The 18S rRNA gene sequence of the confirmed human babesiosis in the Province had 98.1%-99.8% homology with the sequences of B. microti from different hosts and different geographical regions. And it was in the same branch as the human-source B. microti from Yunnan and Japan, and the rodent-source B. microti from Fujian, and Hangzhou, Tiantai and Xianju of Zhejiang. The Chinese CNMM-2 strain and Xinjiang 1647 strain of B. microti had a closer genetic distance with American GI strain and German Jena strain. Conclusion The B. microti was commonly found in rodents in the central and south areas of Zhejiang Province. Studies should be extended to other small mammals and domestic livestock, as well as to the biological vectors to see if they are carrying Babesia species pathogenic to humans.

Key words: Babesia, Babesia microti, 18S rRNA, Phylogenetic analysis