Transmission electron microscopical studies of the site of attachment of Ancylostoma ceylanicum to the small bowel mucosa of the dog.

The host-parasite interaction at the site of attachment of the adult hookworm, Ancylostoma ceylanicum, to the small bowel mucosa of the dog has been examined by transmission electron microscopy. The lamina propria around the heads of the worms showed intense infiltration with neutrophilic and eosinophilic leucocytes, and plasma cells were also prominent. Erythrocytes were extravasated within the lamina propria while the portions of mucosa engulfed into the buccal cavities of the worms were necrotic and included aggregates of collagen fibres. Within the lumina of the worms were erythrocytes in varying stages of lysis together with other necrotic debris. The mucous membrane adjacent to the heads of the worms was ulcerated while more distant enterocytes were small, distorted and displayed various degrees of microvillar loss. Many mucosal blood vessels had platelet aggregates within their lumina but no fibrin deposition was observed. Vessels were often seen in the bases of the ulcers and were prone to rupture. Erythrocytes and leucocytes were seen in the dog intestinal lumen in close proximity to the bodies of the worms.