| The avian reovirus virus exists worldwide, which can infect chickens, ducks, geese and other avian species. The clinical symptoms of infected fowls were variation and complex. In1997, the duck reovirus was first isolated from the Muscovy duck flock characterized with paralysis and necrosis of liver and spleen in Southern China which caused substantial economic losses to duck industry. One stain of duck reovirus named ZY/AH/1/2011was isolated from the duck group by our laboratory. The biological characteristics of this strain were studied in detail. We used the isolated strain to produce an oil emulsion inactivated vaccine and evaluated its initial immune efficacy.1Identification of duck reovirus ZY/AH/1/2011causing egg dropWe collected samples from a duck flock in congyang in Anhui province, and inoculated through allantoic cavity of duck embryo. The death duck embryo allantoic fluid was collected, and PCR detection showed only avian reovirus was found while on other co-infection were found. We observed the virus’s morphology through phosphotungstic acid negative staining and ultrathin sections, we found that the virus was round, about70nm in diameter, non-enveloped, double capsid structure. This virus was treated by chloroform, processing temperatures and different pH environment and we found this strain was resistive with heat, acid, but sensitive to chloroform.We designed a pair of primers according to duck reovirus σB gene from GenBank, and determined the part of the σB gene sequences through RT-PCR. The analysis of σB gene sequence showed that this strain shared low identities with other duck reovirus. The identity is57.7%-64.8%. They located in different branches in the phylogenetic tree. What’s more, there are significant differences in130aa to139aa at the epitope.After artificially infected the132-day-old shelducks using the strain reovirus ZY/AH/1/2011, the egg production of the shelducks dropped from70%to about20%. When dissecting the dead ducks, the infected duck showed eggs deformation and degeneration, tubal atrophy. Results of histopathological tests showed local ovarian necrosis, a small amount of hemosiderin, reduced the number of eggs and a large number of heterophil granulocyte infiltration; while varying degrees of inflammatory cell infiltration tubal edema, submucosa, and interstitial oviduct pseudo stratified columnar epithelial cells into stratified epithelial cells and large numbers of lymphocyte infiltration in the spleen.In summary, compared with the previously reported duck reovirus, the biological characteristics of the reovirus ZY/AH/1/2011causing egg production decline were quite different.2Preparation of the inactivated oil emulsion vaccineIn this study, we used the isolated strain reovirus ZY/AH/1/2011to produce a oil emulsion inactivated vaccine. The physical properties and safety test showed the inactivated oil emulsion vaccine indicators were qualified. The ducks were divided into four groups, immunization and challenge group, immunization but not challenge group, unimmunization but challenge group, and the healthy control group. We immuned the130-day-old shelducks with the vaccines through neck subcutaneous at the dosage of0.5mL per duck.14days post immunization, we challenged with the strain reovirus ZY/AH/1/2011, and observed15days, the result showed that the immunization group can get good protection, and the average egg production rate was about70%, the difference was not significant with the healthy control group, while the rate of the challenge group reduced to16.7%. Duck reovirus antibody titers were detected by the ELISA, the results showed7days post immunization, the immunization group antibody positive rate was100%. The antibody titers in21days post immunization reached the highest. Safety inspection showed no adverse reaction to testing duck.These results indicate that the oil emulsion inactivated vaccine was safe and effective, and it can be used to protect ducks from infection of duck reovirus virus. |
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