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Abstract:
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(En)
Initial studies conducted in CMRDC Project DAW 7CM resulted in the development of highly specific and sensitive antibody ELISA for BLS that was capable of detecting flock infection at an earlier stage than the existing serological test for Big Liver and Spleen Disease (BLS), the agarose gel immunodiffusion test (AGID). A laboratory based procedure for titration of virus infectivity was developed and evaluated. The new tests were used in a series of studies to investigate the transmission of BLS in broiler reeder flocks and in experimental transmission pen studies. These showed that the most efficient transmission occurred by direct contact, probably via faecal-oral spread but aerosol spread could occur over limited distances and there was field evidence y allowing virus infectivity and viral antigens to be tracked during purification and characterisation procedures. The causative virus is yet to be fully characterised but so far it has been shown that the infectious particle is an RNA virus, between 50
nd 100 nm in size by filtration studies, has a buoyant density in sucrose gradients of 1.20 - 1.22 g/ml, and replicates in the cytoplasm of infected cells. Infectivity by chick embryo inoculation is not inhibited to any significant degree by ether or ch
s developed and standardised, serum from these birds was shown to have a low level of neutralising antibody equivalent to levels found in convalescent serum from BLS infected birds. This suggested it was worth persevering with vaccination development st
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