Ingestion of host immunoglobulin by three non-blood-feeding nematode parasites of ruminants

Host immunoglobulin was detected in homogenates of adult worms or fourth stage larvae of Haemonchus contortus, Ostertagia ostertagi, O circumcincta and Dictyocaulus viviparus, but not in preparasitic third stage larvae of H contortus. All the worms had been washed in detergent before being homogenised to remove any immunoglobulin adhering to the cuticle. This procedure, the concentrations of immunoglobulin detected and observations on sections of the worms stained with fluorescent antisheep immunoglobulin, all suggested that the immunoglobulin had been ingested, even by the non-blood-feeding species. This finding suggests that the Ostertagia species and D viviparus may be susceptible to vaccination by the gut antigen approach, a method with considerable promise for blood-feeding parasites like H contortus and Boophilus microplus.