The Influence of Sample Quality and Elisa Kits on the Occurrence of Single Reactors in Serological Diagnostics of Foot-and-Mouth Disease and Peste Des Petits Ruminants

Abstract Regular monitoring of susceptible animal species for specific antibodies is essential to achieve or to maintain disease-free status for a country. The absence of certain disease in a country for many decades would yield expectation that collected animal serums would be negative for the presence of specific antibodies. However, large-scale tests often dismiss single-reactor findings as poor sample quality. The current study aimed to investigate the effect of storage conditions of negative serum samples and the specificity of ELISA kits on the test results, focusing on two key livestock diseases: foot-and-mouth disease (FMD) and peste des petits ruminants (PPR). Serum samples from bovine and ovine sources were stored at varying temperatures and durations, were subjected to freeze-thaw cycles, and were retested. Results were compared with zero-day tests which were considered to be truly accurate and negative. The quality of ELISA test results is less significantly affected by serum samples quality (affected by temperature, storage time, and freeze-thaw cycles) and occurrence of false positive single reactors, than the diagnostic specificity of different ELISA lots. This study challenges the conventional justification for single-reactor findings and underscores the importance of ELISA kit quality.