Department of Veterinary Microbiology, College of Veterinary Science and Animal Husbandry, Anand Agricultural University, Anand.
Abstracts of Research Papers Presented during the National Symposium of Indian Virological Society at Unit of Plant Virology, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi-110 012, October 14–1.
Infectious bursal disease (IBD), an economically important infectious viral disease of poultry, is caused by Infectious bursal disease virus (IBDV) belonging to Avibirnavirus genus of Birnaviridae family. The disease causes considerable morbidity and mortality mainly by immunosuppression.
The present study aimed at screening IBD suspected bursal samples by Reverse transcription-polymerase chain reaction (RT-PCR) and conventional precipitation assays viz. Agar gel immunodiffusion (AGID), Single radial immunodiffusion (SRID) and Counter immunoelectrophoresis (CIE) were employed so as to compare their relative sensitivity with RT-PCR as well as among themselves. Two viral RNA extraction protocols viz. phenol-chloroform and Tri Reagent® method were compared for their efficacy and suitability for RT-PCR. Processing of the 147 collected samples by AGID, SRID and CIE revealed 70.07, 72.79 and 78.23 per cent positivity respectively. Thirty four samples were from layer birds and 113 from broiler birds, of which, 29 (85.29%) and 86 (76.11%) were positive for IBDV antigen respectively by CIE. The highest incidence was found in the age group > 3 ⌓ 4 weeks age group.
Thirty seven bursal samples and two live IBD vaccines were used for viral RNA extraction by phenol-chloroform method (protocol 1) and Tri Reagent® method (protocol 2). RNA extracted by protocol 1 was of poor quality and quantity, and failed to yield targeted amplification in all the samples and vaccines by RT-PCR, where as protocol 2 yielded RNA of good quality and quantity, and produced targeted amplicon of approximately 643 bp and 557 bp respectively for primer pairs P1, P2 and U2, L2, specific for hypervariable region of IBDVVP2 gene, for 31 (83.78%) samples and two vaccines. All the positive samples behaved similarly to the two pairs of primers, which were equally sensitive in detecting the IBDV.
Sensitivity of AGID, SRID and CIE with RT-PCR was 74.19, 77.42 and 87.10 per cent, while that of AGID and SRID with CIE was 89.57 and 93.04 per cent respectively. Overall agreement of AGID, SRID and CIE with RT-PCR was 78.38, 81.08 and 89.19 per cent, while that of AGID and SRID with CIE was 91.84 and 94.56 per cent respectively. Specificity of all the precipitation assays used with RT-PCR was found 100 per cent.
