Studies On The Pathology Of Layers Inoculated Experimentally With H₉N₂ Subtype Avian Influenza Virus

100 4-day old healthy layers were divided randomly into 2 groups, 50 for the tested group and 50 for the control group. The layers of the tested group were inoculated 0.4ml(107-109EID50) H9N2 subtype virus allantoic fluid of poultery embryo. In a chicken model of layers inoculated with H9N2 subtype avian influenza virus, clinical signs and histopathology were observed and transmissional electron microscope were carried out on the tissues of inoculated layers. At the same time, apoptosis of the immune organ in layers infected with avian influenza virus was demostrated by the nick end-labelling of DNA in situ (TUNEL). Meantime, the serum biochemical value and antibody level were determined after inoculation by intranasal-intraocular.The results showed that layers were dispirited, began to eat little and drank more on 3 day post inoculation. Liver had a change of swelling, and appeared white and yellow necrosed focus. Swelling and petechchiae appeared in kidney and intestines.Histopathological changes showed that liver had disseminated hemorrhage, congestion, Hepatocytes showed degeneration, necrosis. Heavy degeneration and necrosis occurred in the renal tubular epithelial cells. The pathological changes of lung and heart showed hemorrhage. Swelling and hemorrhage occurred in the mucosa of intestines, and there were degeneration, necrosis in the mucosa epithelial cells of intestines. Mucosa were deprived from trachea. The number of lymphocyte reduced sharply in spleen, thytnus and bursa of Fabricius. Eosinophilic inclusion bodies were found in the cytoplasm of hepatocytes and the renal tubular epithelial cells by Mann staining methods for liver and kidney.Transmissional electron microscope showed that some cells had the morphological characteristics of siginificant apoptosis in the spleen, thymus, bursa of Fabricius and caecum tonsil, and morphological changes were condensation of nuclear chromatin into dense masses, followed by itsmarginating against the nuclear envelope, and concentration of cytoplasm association with lots of cytoplasmic vacuolization. Cytoplasm was swollen, cell nuclear was dissolved in the hepatocytes and the renal tubular and epithelial cells. The swelling and distortion appeared in the intravascular cells.The results of the serum biochemical value showed that the level of serum AST, ALT and P began to go up on 3 PID. The value of Ca went down on 7 PID. The level of TP, ALB, GLB, UA, CRE or ChE had no significant differences within the whole period.Antibody against H9N2 subtype AIV was tested with the hemagglutinin inhibition(HI)and the findings indicated that HI antibody began to rise on 3 PID and rose to maximum (1:256) on 14 PID. HI antibody reduced to 1:64 on PID later.The apoptosis levels of immune organs were dynamically observed in the experimental inoculation layers. The result showed that apoptosis levels of spleen, thymus and bursa of Fabricius rose distinctively. The results showed AIV could induce apoptosis of the immune organs in vivo.So we could see that virus followed into the tissues of layers and reproduced in sensitive organs or tissues during the infection. Heavy degeneration and necrosis occurred in liver and kidney. Meantime, apoptosis levels increased sharply in the immune organ. On the other hand, HI antibody levels rose distinctively. The results showed AIV could induce apoptosis and immune reaction in vivo.