Comparative efficacy of enzyme-linked immunosorbent assay (ELISA) and haemagglutination inhibition (HI) tests for measuring humoral immune response against egg drop syndrome virus in layer chicks

Egg drop syndrome is a disease of chicken caused by haemagglutinating atadenovirus virus, which are DNA containing particles 74-80 nm in diameter and replicate in nucleus of the host cells. Infection with the virus causes a failure to reach peak production in flocks affected prior to 20 weeks of age or a decline in peak production from 10-30 percent. The infected birds lay soft- shelled or shell less, discolored and misshapen eggs without any change in the internal duality. In acute cases, there may be mild depression, however, feeding, watering and general appearance of the affected birds remains normal. EDS virus was propagated through duck embryo inoculation. Identification was done through haemagglutination. and inhibition tests using known antiserum. The pooled AAF showed HA titer ranged from log213 to log215, while no HA was evident from rabbit, buffalo, horse and goat. Hyperimmune sera were raised in four rabbits using known EDS vaccine and confirmed through AGP test and highest antibody titer of log211 was recorded through HAI test. Goat-antichicken antibodies were partially purified through ammonium sulphate precipitation technique and total protein contents of immunoglobulins were ranged from 2.957 to 0.139 mg/ml. A 10 mg of horse- radish peroxidase was used to conjugate anti-antibodies by two-step gluteraldehyde method. An indirect enzyme-linked immunosorbent assay (ELISA) for the detection of antibody to a haemagglutinating duck adeno virus was described. Optimum conditions described for the test induced 1 % coating EDS virus with 100 mul volume while, 100 mul of conjugated antibody with 1% concentration were found to give optimum OD value through ELISA test. ELISA showed one to two steps higher antibody titer then HI test in the same serum samples, which may illustrate the ELISA as more sensitive technique than HI test.