Parasitic gastroenteritis caused by Haemonchus contortus (H. contorus) is the major constrain in
Egyptian sheep industry and their impact on production, animal health and welfare is likely to increase. Different
H. contortus antigens in their native form; crude somatic antigen (CSA), crude larval antigen (CLA) and
excretory/secretory antigen (ESA) or partially purified through gel filtration using Sephadex G-100 resulted in
3, 3 and 2 peaked chromatograms, respectively or in a recombinant form as recombinant H. contortus protein
26/23 (rhcp26/23) were prepared, electrophoretically characterized through SDS-PAGE and immunologically
evaluated through indirect ELISA for diagnosis of haemonchosis in experimentally infected sheep. Analysis
of resulted bands in SDS-PAGE demonstrated that the specific bands were 23, 26, 37, 43, 60 and 76 kDa for adult
antigens but 32, 38 and 66 kDa for larval antigens and only 15,24 kDa for excretory/secretory antigens.The result
of indirect Enzyme linked immunosorbent assay (ELISA) of different antigens revealed that peak I of CSA were
sensitive for early detection of haemonchosis in experimental animals (after 1 week of infection) even in low st
antibody titer. So, this antigen conducted in ELISA assay to detect H. contortus antibodies in the slaughtered
animals in comparison with presence of worms in their abomasal content showed 97.24% sensitivity, 65.11%
specificity with 69.09% diagnostic value which mainly due to cross reactivity with other parasitic infections.
The cross reactivity of this antigen judged with antigens and hyperimmune sera of Fasciola and Moniezia
using both ELISA and immunoblotting ensuring our hypothesis. The present study demonstrated that peak
I of CSA had the most immunodiagnostic potency and the capability to elicit humoral immune response in
experimental and natural haemonchosis in sheep.