ARS | Publication request: Mortality of one-week-old chickens during naturally occurring Marek's disease virus infection

Submitted to: Veterinary Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 14, 2010
Publication Date: September 1, 2011
Citation: Carvallo, F.R., French, R.A., Gilbert-Marcheterre, K., Risatti, G., Dunn, J.R., Forster, F., Kiupel, M., Smyth, J.A. 2011. Mortality of one-week-old chickens during naturally occurring Marek's disease virus infection. Veterinary Pathology. 48(5):993-998.

Interpretive Summary: Early mortality syndrome, a condition where chickens die extremely early, has been described under laboratory conditions in chickens infected by some strains of Marek's disease virus (MDV). This syndrome has not been described before in the field with chickens exposed naturally to MDV, a virus that can cause cancer-like disease in susceptible chickens. This case report describes mortality in one-week-old chickens that was associated with MDV infection based on multiple diagnostic tests. Other common diseases that could have contributed to this syndrome were not detected in this field case. Important conclusions are that even in small backyard flocks, MDV can cause early and severe infections and it shows the importance of vaccinating all birds against MDV, even small flocks.

Technical Abstract: Marek’s disease (MD) is a serious economic disease of chickens which occurs worldwide. MD can present as one of several forms, with the most commonly occurring forms being the lymphoproliferative diseases. Under experimental conditions, an early mortality syndrome has been recognized following infection by some, but not all strains of MD virus (MDV). Herein, we present the first report of a confirmed case of mortality due to naturally occurring MDV infection in one-week-old non-vaccinated Rhode Island Red chickens. Necrotizing lesions were observed in the bursa of Fabricius, lung, duodenum, jejunum and proventriculus, and large intranuclear inclusion bodies were a striking feature in lesioned tissues in all birds. Immunohistochemical staining for the pp38 protein of MDV revealed abundant pp38 antigen in the lesioned tissues, confirming the presence of MDV within the lesions. PCR yielded an amplicon with 97% homology to the meq gene of MDV. No evidence of co-infection by either of the immunosuppressive agents chicken anemia virus and infectious bursal disease virus, was detected.