<prompt> The commonest vector of plague is:Xenopsylla cheopisMusca domesticaXenopsylla astiaPulex irritans  <response>: Xenopsylla cheopis is the commonest and the most efficient vector of plague. Other vectors include Xenopsylla astia, Xenopsylla brasiliensis and Pulex irritans. Ref: Park 21st edition: page 268. 