Molecular and pathological characterization of duck enteritis virus in Egypt

In winter 2016, a fatal disease outbreak suspected to be duck virus enteritis (DVE) stroke over a million ducklings in 10 white Pekin and Muscovy ducks flocks in Dakahlia and Gharbia Governorates, Egypt, causing heavy economic losses. The disease quickly killed 20%-60% of affected farms. The clinical signs were inappetence, ataxia, crowding in corners, partially closed eye lids and blue beaks. Post mortem examination revealed white necrotic foci in liver, mottled spleen and sometimes cecal core. A total of 10 intestines, livers and spleens samples were collected from diseased flocks. Each sample was pooled randomly from eight to ten ducklings. Polymerase chain reaction (PCR) and histopathological examination were utilized for DEV identification in collected samples. Nucleotides sequences of the amplified DNA polymerase gene were compared with the other DEVs available on GeneBank. Also, existence of co-infection with Salmonella spp. was verified via PCR. DEV nucleic acid was detected by PCR in 8 of 10 collected samples (80%) with positive amplification of polymerase gene. Histopathological examination revealed eosinophilic and basophilic intranuclear inclusion bodies in enterocytes. In some infected enterocytes, intranuclear and intracytoplasmic inclusions were observed in the same cell. Respectively, eosinophilic intranuclear inclusion bodies found in hepatocytes and reticular cells of liver and spleen of diseased ducklings. Four of the 10 collected samples showed positive results for Salmonella spp. infection that may be involved in enhancing infection with DEV. The identified DEVs revealed close genetic relationship with DEVs detected previously in India and China indicating potential transmission of the virus from there that crucially needs further work for better understanding of virus origin. In conclusion, our study revealed infection of duckling farms with DEV and Salmonella that necessitate the implementation of restricted early preventive and control measures for both diseases to decrease the expected economic losses.