Authors’ contributions
Jian
Zhang and Ben W. Mol conceived and
designed this study; Jian Zhang, JAF Hurine and Ben W. Mol contributed
to the manuscript editing and language editing;
Li Yan was responsible for the data
analysis and manuscript writing; Chenfeng Zhu, Guiling Liang, Chuqing
He, Yan Liang, Xiaoya Zhao, Xiaoqing He and Yiqin Zhang contributed to
the data collection. The final version of manuscript has been approved
by all authors.