Acknowledgements
This study was partly supported by a Grant-in-Aid for Scientific Research (No.25292171 and 16H05027) and the Grant for Joint Research Program of the Research Center for Zoonosis Control, Hokkaido University, from the Ministry of Education, Culture, Sports, Science and Technology, Japan. This study was also supported in part by the Ito Foundation.
Declaration of interest
The authors report no conflicts of interest.