Genetic Diversity and Coexistence of Babesia in Ticks (Acari: Ixodidae) from Northeastern

Abstract

BackgroundBabesiosis is an emerging zoonosis in humans with significant and increasing health burden in China. A few systematic reports on Babesia spp. was involved with ticks, especially in the human babesiosis endemic areas.\n\nMethodsThe ticks were collected from 30 individual waypoints along 2.0 km transects in two recreational forested areas in Northeastern China. Then we screened them for Babesia spp. infection by amplifying the partial 18s rRNA gene with subsequent sequencing. Multivariate logistic regression analysis was used to access the association between infections and some related risk factors. The cluster analyses were performed using SaTScan v6.0 Software for identifying the geographic cluster of the positive samples in ticks from each waypoint.\n\nResultsA total of Ixodes persulcatus (n=2380) and Haemaphysalis concinna (n=461) ticks were collected. The 0.97% of I. persulcatus ticks were infected with five Babesia species, including B. bigemina (n=6), B. divergens (n=2), B. microti (n=3), B. venatorum (n=11) and one novel strain HLJ-8. Thirteen (2.92%) H.concinna ticks contained B. bigemina (n=1), B. divergens (n=1), three genetic variants of Babesia represented by HLJ-874 which was closely related to Babesia sp.MA#361-1, and eight other Babesia variants represented by HLJ242 which were similar to B.crassa. Each study site had 5~6 different Babesia spp. One waypoint was more likely to yield B.venatorum (relative risk=15.36, P=0.045) than all other waypoints.\n\nConclusionsThere exists a high genetic diversity of Babesia spp. across a relatively small sampled region. Further study is needed to understand the risks these variants pose for human health.\n\nAuthor SummaryBabesiosis is the subject of increasing interest as an emerging zoonosis in humans with significant and increasing health burden of the disease at recently. In China, many probably human babesiosis cases who had a history of recent tick bite were found in Lyme endemic area in Northeastern China, where the prevalence of Babesia parasite in the ticks still was far underestimated. In the present study, we conducted a field survey for ticks to identify diversities and complexity of babesia, and then to assess the risk of human babesiosis, by means of a three years longitudinal study that mapped the location of the ticks tested positive for Babesia spp. at two forestry areas with a heavy burden of tick-borne pathogens. We firstly presented the prevalence of Babesia spp. especially the genetic diversities and coexistence of seven Babesia spp. including 2 novel species or variants at one small scale \"natural foci\" in northeastern China. This work is useful to understand the complexity of Babesia pathogen in China, and how the Babesia perpetuates over the long term in the environment, as well as potential risks for human health.