Fig. 5
From: Poor vector competence of the human flea, Pulex irritans, to transmit Yersinia pestis
Proventricular blockage in P. irritans infected with green fluorescent protein-expressing Y. pestis in rat blood. A Immediately after this flea attempted to feed 6 days after infection, fresh red blood was present only in the esophagus (delineated by the white arrows) anterior to the proventriculus (PV). No fresh blood was present in the midgut (MG), which contains only dark-colored remnants of previous blood meals. Light (B) and fluorescence (C) microscopy of the digestive tract dissected from this flea shows the dense bacterial biofilm aggregate that fills the proventriculus and blocked the flow of blood from the esophagus (E)