EVALUATION OF A COMMERCIAL ELISA TEST KIT ON CLASSICAL SWINE FEVER ANTIBODY DETECTION USING ORAL FLUID SAMPLES

Abstract

Classical swine fever (CSF) is a devastating disease, contributing to economic loss of swine production in endemic countries. Monitoring the swine herd status from this disease is crucial for the prevention and control program. Many diagnostic assays have been developed and used for the detection and monitoring of CSF antibody, which often include blood collection procedure causing stress for the animals, time consuming, needs labor and many equipments. Recently, the collection method for swine oral fluid samples was developed and used in the detection of pathogens and antibody such as PCV-2 and PRRSV. This particular method is not only less stressful to the animals, but it is simple and practical for both farmers and veterinarians. In addition, the use of enzyme-linked immunosorbent assays (ELISA) is a safer and less expensive way in the detection of antibody and antigen for CSF in disease free country. This experiment obtained oral fluid samples and blood samples from previous experiment which divided a total of 20 piglets (20 days old) into 3 experimental groups; challenged with ALD strain, a low virulence (A) (n=8), vaccination (B) (n=8) and negative control (C) (n=4). The animals were vaccinated with modified live vaccine (MLV) at 0 day post inoculation (dpi) and re-challenged (A&B) with Bangkok 1950 strain, a high virulence on 14 dpi and euthanized at 30 dpi. Oral fluid samples were collected daily by hanging cotton ropes in each pen and fluid was extracted from the ropes by mechanical compression and blood samples were collected on -1, 3, 7, 10, 14, 17, 21, 24, 27 and 30 dpi. A commercial classical swine fever indirect ELISA test kit (BioChekCSFV Antibody Test Kit, Reeuwijk, The Netherlands) was used in the detection of CSF antibody in oral fluid samples with normal protocol and modified oral fluid concentration. The sensitivity of the ELISA was evaluated using known negative oral fluid combined with serum of known serum neutralizing titers. The results demonstrate that CSFV antibody could be detected using indirect ELISA assay and the longer incubation time enhanced the antibody detection signal. Using the oral fluid obtained from experimental animals with the normal ELISA protocol and NPLA test, the results showed low detectable antibody titers from both tests. By using the modified ELISA protocol, the sensitivity increased in the known CSF NPLA titers of oral fluid samples. With the use of oral fluid samples from the challenged experiment, the ELISA was able to detect low amount of CSF antibody titers in the oral fluid using the modified protocol. This proved that anti-CSFV antibody could be detected from oral fluid samples with the indirect ELISA and this test could be used to further in the monitoring and surveillance program of CSFV in the future.