Received: 12 January 2019
Accepted: 3 July 2019
First Online: 8 July 2019
Ethics approval and consent to participate
: This study was approved by the ethics committee in the National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention (reference no. 2012–03). A written informed consent form was obtained from the guardian of each participant.
: Not applicable.
: The authors declare that they have no competing interests.