|METE, ALSI - University Of California|
|PITESKY, MAURICE - University Of California|
|GHARPURE, RADHIKA - University Of California|
|FAMINI, DAN - Santa Rosa Junior College|
|SVERLOW, KAREN - University Of California|
Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/13/2016
Publication Date: 9/19/2016
Publication URL: http://handle.nal.usda.gov/10113/5592323
Citation: Mete, A., Pitesky, M.E., Gharpure, R., Famini, D., Sverlow, K., Dunn, J.R. 2016. Marek's disease in backyard chickens, a study of pathological findings and viral loads in tumorous and non-tumorous birds. Avian Diseases. 60(4):826-836. doi: 10.1637/11458-062216-Reg.
Interpretive Summary: Marek’s disease (MD) is currently the most diagnosed viral disease in backyard chickens. The purpose of this study was to evaluate advanced methods (quantitative PCR) to diagnose MD using samples from backyard chickens submitted to UC Davis. The results were a high correlation of virus load measured by the advanced methods compared to severity of lesions measured by the traditional methods of examining histological sections using a microscope. These results provide validation for using the advanced methods in a clinical setting of backyard chickens which should provide faster diagnosis or aid in cases where diagnosis unclear by traditional methods alone.
Technical Abstract: Marek’s disease (MD) is a major cause of mortality in backyard chickens. The diagnosis of MD is complex, however, and knowledge on Marek’s disease virus (MDV) in spontaneous field cases such as in backyard chickens is largely unknown. Forty backyard chickens with presumptive MD diagnosis based on histological lymphoid infiltrations in peripheral nerves with and without lymphomas were investigated. Twenty-eight of the birds were submitted to the diagnostic laboratory for disease explorations, and 12 chickens were from a flock where some demonstrated anisocoria and pupil irregularities compatible with ocular MD. Histological scores were established for brain, peripheral nerves, heart, lung, liver, kidney and gonad sections, ranging from mild (+) to severe (+++) lymphoid infiltrations. Twelve chickens had gross lymphomas, all but two chickens had mild to severe peripheral nerve lymphoid infiltrates. There were no age or breed predispositions in the study group. Quantification of serotypes MDV-1, 2 and 3 performed using real-time PCR demonstrated good correlations between fresh and fixed spleen specimens, as well as between histopathology scores and MDV-1 viral loads. MDV-2 DNA was detected in a portion of the chickens, likely consistent with naturally occurring virus, whereas the vaccine strain MDV-3 was rarely detected. Significant differences in MDV-1 viral loads between tumorous and non-tumorous chickens were observed, where a ratio of MDV-1 gB/GAPDH >0.5 was suggestive of gross tumors in this study.