Transmission of avian viruses both bird-to-bird and from birds to non-avian species is a major health concern. Newcastle disease virus (NDV) is an economically important avian virus that poses substantial risks to the poultry industry. Rapid and sensitive diagnostic methods, such as the enzyme-linked immunosorbent assay (ELISA), are required to track such infections. To develop an ELISA for detecting anti-NDV antibody in avian sera, the nucleocapsid protein (NCP) gene of the NDV La Sota strain was cloned and expressed in Escherichia coli and the 513-amino acid recombinant NCP was purified by Ni-NTA affinity chromatography. To evaluate its ability to replace NDV whole virus antigen as a coating antigen, NCP-coated and whole NDV-coated ELISAs were tested and compared using a panel of NDV positive antisera from chickens. Results using purified NCP were highly correlated with those obtained using whole NDV (r=0.927), demonstrating that recombinant NCP expressed in Escherichia coli is a suitable substitute antigen for whole NDV in a diagnostic ELISA.

Paratuberculosis caused by Mycobacterium avium subspecies paratuberculosis (Mpt) is a chronic infectious enteric disease with deleterious impact on the performance in ruminants. In Korea, ELISA has been introduced to detect antibodies to Mpt in individual cattle. However, comparison study with ELISA has not been studied until now. In total, a panel of 899 serum samples obtained from dairy cattle was analyzed with two commercial ELISAs for Mpt to assess the performance. Two ELISAs employed in this study were both licensed worldwide. Two ELISAs applied onto same serum samples showed the morderate agreement (kappa value = 0.06). There was non-significant McNemar test (p=0.0614) between two ELISA results indicating that each proportion detected by two kits did not differ. In addition, the percent agreement between two ELISA results was turned out to be 96.8% which interpreted excellent reproducibility. It was shown from this study that two ELISAs revealed moderate kappa agreement performance. The implication raised is that when ELISAs as diagnostics are used to detect Mpt in individual cattle, positive reaction by either ELISA should be interpreted as serologically Mpt positive due to presumed low sensitivity of ELISAs and their test agreement being less than 100%.

This study was conducted to survey of Ehrlichia (E.) canis and Borrelia (B.) burgdorferi antibodies among clinically healthy German shepherd dogs (116 females and 120 males) using a ELISA kit (SNAP 3Dx; IDEXX Laboratories, USA) in Korea. Whole blood samples are collected from the 236 dogs and are tested to detect E. canis and B. burgdorferi antibodies by using ELISA kit (SNAP 3Dx; IDEXX Laboratories, USA). Confidence interval comparisions revealed that dogs of 4-6 years have higher prevalence with a seropositive result (CI = 0.17 - 0.45) in E. canis than the other age groups but there are no differences among age groups in B. burgdorferi.