Suitability of individual and bulk milk samples to investigate the humoral immune responses to LSD vaccination

Abstract

The commercially available ID Screen® Capripox double antigen ELISA from IDvet® validated and authorized for serum and plasma, recently improved the options for assessing the humoral immune response against lumpy skin disease (LSD). In this study, the suitability of milk (individual and bulk) and colostrum as samples for this ELISA was investigated. Samples (serum, milk and colostrum) were collected three times (before, one and five months post re-vaccination) in LSDV-field strain free regions in Serbia. Test specificity was confirmed by analyzing of 352 individual milk samples from Germany. From 154 collected serum samples from Serbia, 75 were detected as positive by the Capripox ELISA. Milk samples were tested using protocol for serum and with a modified protocol (increased incubation time). Obtained results of milk and colostrum samples were analyzed with reduced cutoff value. Out of 154 milk samples, 38 samples were detected as positive using the protocol for serum, whereas with modified protocol the number of positive sample increased up to 48. Only two milk samples from Germany had border line results with the modified protocol. Sensitivity and specificity of the ELISA for milk samples reached values in-between 88% to 91%, with significant statistical difference (p<0.05) between both protocols. In addition, antibody detection was possible in bulk milk and colostrum samples. In principle, the commercially available Capripox ELISA, developed for antibody detection in serum and plasma, shows to be suitable for detection of LSD-specific antibodies in milk samples and can be a helpful tool in LSDV monitoring programs.