|SA E SILVA, MARIANA - Former ARS Employee|
|SUSTA, LEONARDO - Former ARS Employee|
Submitted to: Avian Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2015
Publication Date: 3/17/2016
Publication URL: http://handle.nal.usda.gov/10113/5156703
Citation: Sa E Silva, M., Susta, L., Moresco, K.A., Swayne, D.E. 2016. Vaccination of chickens decreased Newcastle disease virus contamination in eggs. Avian Pathology. 45(1):38-45. doi: 10.1080/03079457.2015.1112876.
Interpretive Summary: Newcastle disease is an important disease for the poultry industry. The use of vaccination as a control tool is important, but it is unknown if vaccination can decrease or prevent the virus to be spread via contaminated eggs. For this study, hens were vaccinated once or twice with an inactivated LaSota vaccine, and later challenged with a virulent Newcastle disease virus. Eggs were collected daily and external and internal components (shell, albumen, and yolk) were evaluated for the presence of viable virus, as well as respiratory and digestive tract samples collected 2 and 4 days after challenge. The vaccine, both administered once and twice was capable of protect against mortality and decrease the presence of virus in the eggs and in digestive and respiratory tracts. The virus was identified throughout the oviduct of non-vaccinated challenged hens. The results of these experiments suggest that the Newcastle disease virus was able to replicate in the reproductive tract but vaccination prevented dissemination of the virus to egg components, reducing the risk for commercial trade.
Technical Abstract: Newcastle disease is an important health issue of poultry causing major economic losses and inhibits trade worldwide. Vaccination is used as a control measure, but it is unknown whether vaccination will prevent virus contamination of eggs. In this study, hens were sham-vaccinated or received one or two doses of inactivated LaSota vaccine, followed three weeks later by virulent Newcastle disease virus (NDV) challenge. Eggs were collected daily and shell, albumen and yolk were subjected to virus isolation, as were oral and cloacal swabs at 2 and 4 days post-challenge (dpc). A second experiment evaluated the distribution of the virus in the reproductive tract of non-vaccinates. All vaccinated chickens survived challenge, and the levels of virus shed from cloacal swabs were decreased significantly when compared to shams. In non-vaccinated hens, virus was detected in the ovary and all segments of the oviduct. Yolk, albumen and eggshell surface from eggs laid at day 4 and 5 post-infection by sham-vaccinated hens were positive for NDV, but eggs from LaSota vaccinated hens lacked virus in internal egg components (i.e. yolk and albumen) and had reduction in the number of positive eggshell surfaces. These results indicate virulent NDV can replicate in the reproductive tract of hens and contaminate internal components of eggs and eggshell surface, but vaccination was able to prevent internal egg contamination, reducing eggshell surface contamination, and reducing shedding from digestive and respiratory tracts in virulent NDV challenged hens.