Pathogenesis Of Duck Tembusu Virus In One-week-old Ducklings

To study the pathogenicity of duck Tembusu virus in Cherry Valley ducklings, infection model was established to dynamically supervise clinical symptoms, pathological changes, tissue viral loads and immune responses of infected ducklings after one-week-old ducklings were inoculated intramuscularly with Tembusu virus FX2010 strain, the ducklings showed loss of appetite and yellow-white stools at the third day post infection(3dpi) and neurological symptoms at 5dpi. In addition, some ducklings died acutely and the mortality rate was 22.5%(9/40). Necropsy showed endocardial hemorrhage, swelling and necrosis in spleen. The liver and kidney were degenerative and swelling and meningeal congestion. Histopathological changes in infected ducklings mainly presented as degeneration and necrosis in parenchymal cells of heart, liver and kidney, interstitial inflammatory cells were infiltrated or bleeding, focal lymphocytes necrosis and a large number of heterophilic granulocytes infiltration in spleen, typical viral encephalitis in brain. Tembusu virus could be detected in every organ of infected ducklings at 1dpi and viral levels reached a peak at 3dpi in all organs except for the spleen. The levels of serum neutralizing antibodies were low at 5dpi, then gradually increased and reached the peaks till 17 dpi. These results suggested that duck Tembusu virus could quickly invade tissues and numerously replicate in affected ducklings, characterized by pantropic virus injuring most tissues. Severe ducklings usually died of acute septicemia. The neutralizing antibodies could be rapidly produced to fight against infections and eliminate the virus.