Studies On Pathogenicity Of Tembusu Virus For Goslings

In China many egg-laying ducks farms and breeder geese farms had suffered from a serious infectious disease with the main clinical symptoms in sever egg production decrease since April 2010, and had identified the pathogen was TMUV(Tembusu Virus). TMUV infection ducks primarily, while it’s could infection in geese and caused infected geese morbidity and death. Breeder geese infected in TMUV mainly lead to egg production decrease obviously, while the results of goslings inoculated in TMUV is with highly morbidity, many serious pathogenetic goslings went to death ultimately, and had caused to a huge economic loss in our countries goose industry. To investigate the pathology of TMUV in goslings, this study was chose TMUV-SDSG strain inoculated in 5-day-old goslings and 20-day-old goslings respectively, and TMUV-SDSG Strain was isolated in ducks from the institute of poultry disease at Shandong Agricultural University. The purpose of this study is to provide a theoretical basis to prevent and control TMUV for goslings in future.Total 100 healthy 1-day-old goslings were equally divided in 5 groups, group one to group four are experimental groups, group five is the control goslings. Group one and two are5-day-old goslings, group three and four are 20-day-old goslings were inoculated with TMUV-SDSG strain(ELD50 10-2.17/0.2m L) in intravenous injection and intranasal drip,respectively. Group 5 goslings were inoculated with the same volume of sterile physiological saline. After infected in TMUV autopsies observed the autopsy symptoms congestion, each group goslings were chose 3 randomly and made periodically to get brains, livers, lungs,pancreas, spleens and other tissues from to at 3dpi, 6dpi, 9dpi, and 12 dpi. Then from the follow three aspects such as to observe the histopathological lesions, the viral load through real time RT-PCR and cytokines test to investigate the pathogenicity of Tembusu Virus for goslings.The results showed that the primarily clinical signs of 5-day-old goslings infected in TMUV through intravenous injection attacked at 4dpi, and the young gosling inoculated TMUV in intranasal drip attacked at 5 dpi. All morbidity goslings were with the main clinical signs including listlessness, inappetence, passage white and green loose stools, legs-weak,marked incoordination, tremble, slow-growing, belly upward with legs struggle as swimming,opisthotonos, and then to death, while the signs of head and neck tremble was showed occasionally. Goslings infected in TMUV through intravenous injection began to death at 5dpi and the intranasal drip groups began to death at 6di. The morbidity and mortality time were focused on 4~8 dpi and 5~8dpi, respectively. And the clinical signs began to relieve at 9dpi.20-old-day goslings infected in TMUV began to showed clinical signs at 5dpi with through intravenous injection, and the course of disease last about 3dpi, however the clinical signs disappear at 8~9 dpi in feed intake rise again. To compare the body weight between 5-day-old goslings and 20-day-old goslings infected in TMUV showed that the younger groups loose higher weight than the older goslings relative to the control goslings at 3dpi, 6dpi, 9dpi,and12 dpi.During autopsy symptoms the gross lesions mainly included congestion, hemorrhagic and dropsical. Gross lesions were observed in most infected goslings organs included hyperaemia,meningorrhagia and encephalitis in brain, myocardial intima haemorrhages and necrosis,hyperaemia in glandular stomach nipple, pneumonedema and pulmonary congestion in lungs,hyperaemia and necrosis in livers, necrosis foci in pancreas, splenomegaly and haemorrhages in spleen, haemorrhages in kidney and so on.The primary microscopic lesions were congestion, hemorrhage, necrosis, massive infiltration of mononuclear cells consisting of lymphocytes, plasma cells, and histiocytes and lymphoid nodules. The lesions of brain showed a viral encephalitis change with perivascular space increased, encephaledema, glialnodule and massive microglia proliferation in brain parenchyma. The congestion of vessel, massive infiltration of mononuclear cells and massive inflammatory cells infiltration were found in the cerebral cortex at. The lesions of liver,kidney, pancreas mainly consisted of degenerate tubules with vacuolated epithelial cells,hyperemia and haemorrhage, and inflammatory cell disintegration. Spleen lesions contained hemorrhage, massive lymphocytes. Lesions of heart included cardiac muscle cells disruption,cardiac muscle fibers hemorrhage, massive infiltration by mononuclear cells, fragmetation of the myocardium and myocyte necrosis. And finally the lesions of lung included haemorrhage and pulmonary congestion.According to the above, qRT-PCR were detected to investigated the antigen of TMUV distributions in different tissues at 3dpi, 6dpi, 9dpi, and 12 dpi. The result showed that and the highest level of viral copies was found in brain and pancreas, heart, spleen, kidney, intestines,thymus, bursa and glandular stomach were take second place,while the lowest were liver and lung. All tissues could detect the relative expression of TMUV at 3 dpi, and the viral load achieved peck at 6dpi, and then to decrease. The relative expression didn’t detect at 12 dpi in liver, lung, thymus and glandular stomach. To compared 5-day-old infected groups and20-day-old groups, the viral load in the younger goslings are more than 10 times as the20-day-old goslings.The result of IL-4 and IFN-γ showed that, the load of IL-4 and IFN-γgoslings infected in TMUV was lower than the control group at 3 dpi and 6dpi, and then began to raised up at9 dpi. The infected goslings didn’t test obvious differences compared with the healthy geese at3 dpi, and the load of IL-4 and IFN-γ began to higher than the control group at 12 dip.The result of antibody levels showed that the serum could detected TMUV antibody levels at 6dpi, then reached at 9dpi and 12 dpi.In conclusion, goslings were sensitive to TMUV with that not only did age-related differences in the resistance to TMUV infection were observed younger geese being more susceptible, but also infected ways diversity could influenced the outcome that intravenous injection geese were more severe than intranasal drip geese. So in clinical process, we should pay more attention to the pathogenicity of TMUV for goslings, and do well operation for TMUV prevention and treatment.