Wide Distribution and Genetic Diversity of Babesia microti in Small Mammals from Yunnan Province, Southwestern China

Abstract

BackgroundBabesia, usually found in wild and domestic mammals worldwide, have recently been responsible for emerging malaria-like zoonosis in infected patients. Human B. microti infection has been identified in China, primarily in the Southwest along the Myanmar border but little direct surveillance of B. microti infection in rodents has been carried out here (Yunnan province). In this region, a diverse topographic range combined with tropical moisture sustains a high biodiversity of small mammals, which might play important role on Babesia transmission.MethodsSmall mammals were captured in 141 sample locations from 18 counties located Yunnan Province, and screened for B. microti-like parasites infection by a nested PCR to target 18S rRNA gene of Babesia, plus directly sequencing for positive samples. Univariate and multivariate forward stepwise logistic regression analysis was used to access the association between infections and some related risk factors.ResultsInfection with Babesia microti was confirmed in 2.4% (53/ 2204) of small mammals. Significant differences in prevalence rates of B. microti were observed based on variations in forest, agricultural, and residential landscapes. Furthermore, adult small mammals had higher prevalence rates than younger, pubertal mammals. The near full-length 18S rRNA gene revealed that there were two types of B. microti, Kobe and Otsu, which demonstrate the genetic diversity and regional distribution.ConclusionsThere exists a wide distribution and genetic diversity of endemic B. microti in Southwestern China, warranting further investigations and monitoring of clinical disease in individuals presenting with Babesia like symptoms in these areas.

High prevalence of Babesia microti in small mammals in Beijing

“…Additionally, further consideration should be given for any patient exposures to certain ecological habitat types-specifically broad-leaved forest, shrub, and cropland-as this study has shown that such exposure is considered to be an important risk factor (Tables 3 and 4). Ecological habitat type of forest was also found to be an important risk factor for B. microti infection in other studies in Yunnan [26,27] and in Southeast Asia [28]. Thus, these findings show that forests, the natural habitat for ticks, likely represent areas of high risk for transmission of B. microti to humans, and as such, people either working in or traveling to the forest, should utilize adequate protection.…”

“…Hence, the identification of U.S.-type in this study revealed the genetic diversity of B. microti in small mammals in Beijing, as well as that in China as a whole. Previously, the most highly recorded genotype of B. microti was the Kobe-type, including those recorded from Yunnan [26,27], Zhejiang, Fujian, and Taiwan [30,31]. Babesia microti of Ostu-type was also detected from Yunnan province [26,27].…”

“…There are some limitations of our study. 1We did not choose nested PCR, which was used in many relevant investigations [27,35]. However, the risks of contaminations during the performance of nested PCR are high, especially when the sample size is large (a total of 1391 samples in our study).…”

“…Previously, the most highly recorded genotype of B. microti was the Kobe-type, including those recorded from Yunnan [26,27], Zhejiang, Fujian, and Taiwan [30,31]. Babesia microti of Ostu-type was also detected from Yunnan province [26,27]. U.S.-type B. microti was only reported from rodents from Xinjiang [16].…”

Infestation and seasonal fluctuation of chigger mites on the Southeast Asian house rat (Rattus brunneusculus) in southern Yunnan Province, China

“…The Southeast Asian house rat, Rattus brunneusculus , was named by Hodgson in 1845. Although some scholars considered R. brunneusculus a synonym of the Asian house rat, R. tanezumi Temminck, 1844 ( Alfred, 2005 ; Ellerman, 1961 ; Wilson and Reeder, 2005 ), more scientists believe that R. brunneusculus is an independent rat species, which is obviously different from R. tanezumi in morphology ( Dhananjoy et al, 2014a , Dhananjoy et al, 2014b ; Gao et al, 2017 ; Wang, 2003 ). The Southeast Asian house rat is not only an important agricultural and forestry pest, but also an important reservoir host and infection source of some zoonoses (plague, HFRS, and scrub typhus, etc.)…”