Table 1_Molecular epidemiology of Babesia microti in southern Zhejiang: an integrated survey of humans, rodent reservoirs, and tick vectors (2020–2023).docx

BackgroundBabesia, an intraerythrocytic protozoan, is globally distributed and poses a significant public health burden. In China, human babesiosis is mainly caused by Babesia microti, and the Zhejiang Province is endemic. This study aimed to determine the prevalence of B. microti in the population, reservoir hosts, and vectors; assess population exposure risks; and gain further insight into the genotype structure in Zhejiang.
MethodsFrom May 2020 to October 2023, blood samples from local residents and blood donors, as well as blood or liver tissues from rodents and questing or host-attached ticks, were collected from seven counties in southern Zhejiang Province. DNA was extracted for the detection of B. microti and identification of the rodent and tick species. A retrospective investigation was conducted on individuals who tested positive. Positive samples were sequenced for phylogenetic analyses.
ResultsIn total, 4,728 samples were collected, including 2,475 local residents, 358 blood donors, 1,615 rodents, and 280 questing or host-attached ticks. B. microti was detected in six local residents, 71 rodents, and nine ticks, with infection rates of 0.24, 4.40, and 3.21%, respectively. Human infections and positive ticks were found in specific counties, whereas positive rodents were detected in all counties. All six infected individuals were asymptomatic carriers with a history of outdoor activities in forested areas, and four also reported contact with animals. A total of 17 rodent species were identified, among which Niviventer lotipes exhibited the highest risk. The tick species identified included Haemaphysalis longicornis, Ixodes granulatus, Rhipicephalus haemaphysaloides, and Rhipicephalus microplus. Positive samples were detected for both I. granulatus and R. microplus. Sequencing and phylogenetic analyses of the positive samples revealed that all the sequences belonged to the Kobe type.
ConclusionThis study is the first comprehensive report of B. microti infection across its life cycle in Zhejiang Province, revealing a wide prevalence in rodents and ticks. Asymptomatic infections in humans have also been reported. N. lotipes appears to be the predominant rodent reservoir host. In addition, I. granulatus and R. microplus may serve as primary tick vectors. These findings provide valuable information for developing preventive strategies against babesiosis in China.