Isolation And Identification And Studies On Characters Of The Pathogen Of Avian Epidemic Diarrhoea

In this study ,one strain of avian rotavirus was isolated from a chicken with natural diarrthoea.Isolation and cultivation of the rotavirus was attemped by the inoculating on monolayers of Marc 145 cells with a suspension of faecal material containing the rotavirus. Marc 145 cells were suitable for primary isolation and propagation of avian rotavirus.Trypsin appeared essential for the enhancement of infectivity and the occurance of cytopathic effect(CPE). Serum neutralization (SN)N electron microscopy(EM) and analysis of genomic RNA were done to identify and confirm the identity of rotavirus. Some other biological characters of the virus were also studied.The rotavirus isolated from the intestinal contents of commercial chicks was determined to be a group A rotavirus based on RNA electropherotype and neuralization test.The average size for the isolated rotavirus was 80 nm for double-shelled particles and 70 nm for single-shelled particles. Further characterization revealed that the buoyant density in saccharose of 1.35 g/cm3.The TCID50 was 10"462 /ml when avian rotavirus was propagated at nine passage.The rotavirus has resistence to chloroform - ether and pH3.0 60 min.The infectivity was decreased when processed at 50*C 30 min: Iml/lMgC^ can not enhanced it to resistence 50癈 60min.The clinical signs and histology of chicken with epidemic diarrhea in natural and artificial infection were studied. Specific Pathogen-free (SPF) chicken developed diarrhea after 1 day inoculated with avian rotavirus. The characteristic changes of necropsy were dilated ceca , frothy gaseous intestinal contents and shed of mucous membrane of intestine. The histologic lesions were characterized by the remarkable atrophy of intestinal villi, basal vacuolation of enterocytes, increment of the crypt and the villus-to-crypt ratio had significantly decrease.compared withthat of noninoculated control chicks.Besides.intestinal villi become thin and flat.or cubic,also accompanied with necrosis.Many villous enterocytes were detached from the lamina propria and the lamina propria contained a diffuse infiltrate of lymphocytes ,plasma cells,macrophages.The characteristic ultrastructural changes observed by electronmicroscope were swelled mitochondria and dilated endo-plasticreticulum.Ribosome on the surface of endo-plasticreticulum fall off and the number of ribosome within the cell decrease.