Serum H. contortus-specific antibody response as reflected in mean optical density readings following challenge infection with H. contortus, with goats separated into high and low FEC classes or phenotypes, and according to whether they were infected with T. brucei or not, together with a group of naive uninfected control goats. Error bars are not shown on all data sets for clarity. Concurrent infection with T. brucei had no significant influence on H. contortus serum IgG response of either of the two FEC phenotypes. For further details see the legend to Figure 8 and Chiejina et al. [16].