The four commercial indirect MAP ELISAs were only able to detect paratuberculosis positive camel sera when the kit conjugate was replaced with either Protein A or the goat anti-camel IgG conjugates from Bio-X or CVRL. The Triple J conjugate did not perform well in contrast to the findings of Kramsky and co-workers who used this in a similar protocol to detect anti-MAP antibodies in llama and alpaca sera. With the former combinations, the Checkit and ID Screen MAP antigen coated plates showed considerable non-specifc cross- reactivity with paratuberculosis negative camel sera, viz. %S/P values ≥ 25% in 4 and 2 out of 4 negative sera, respectively. The Paratub MAP antigen coated plate/Protein A conjugate combination showed better non-specifcity, although one camel sample E2A which had no history of paratuberculosis showed a % S/P of 27% and also a reduced response in camel 6BI after the second vaccination dose.
Parachek, and in-house MAP antigen coated plates worked well in combination with Protein A conjugate showing acceptable non-specifc cross reactivity (%S/P ≤ 12%), and a good colorimetric signal that provided an excellent anti-MAP immune response in the two vaccinated camels, with a response range of greater than 2 and 1.2 absorbance units in camels 47B and 6BI, respectively, after the second vaccine dose compared to the pre-treatment level. Similar profles were obtained for the in-house ELISA protocol that employed OPD substrate, a format that was in common to other ELISAs in our laboratory. It was therefore concluded, that the in-house MAP ELISA was the method of choice for future studies on
Dromedary, iELISA, Paratuberculosis
