Studies on the pathogenicity of duck tembusu virus strain KPS54A61 using mice and chickens

In Thailand, Flavivirus strain TMUV-KPS54A61 was isolated from mosquitoes and ducks. The pathogenicity of TMUV-KPS54A61 was tested in mice and chickens. The TCID50 of TMUV-KPS54A61 was estimated and a dilute was applied to groups A-D of adult chickens (105, 104, 103, 102 TCID50) and BALB/c mice using intracerebral inoculation. Young chickens were inoculated with 107TCID50 of TMUV-KPS54A61. Adult chickens did not exhibit the clinical signs, while organ samples tested negative by RT-PCR for the genome of TMUV. On the other hand, groups A and B of BALB/c mice and young chickens showed clinical signs including anorexia, hunched posture, fluffy hair, diarrhea and retarded growth. Pathological changes observed including perivascular cuffing, multiple clusters of gliosis in cerebral and cerebellar. Necrosis of the liver cells and interstitial nephritis in the kidney were also found in young chickens, while the spleen and pancreas are unclear the pathological changes. Immunohistochemical staining of mouse spinal cord samples was positive for the virus protein. TMUV-KPS54A61 was detected in the serum, brain, liver, kidney, adrenal gland, pancreas and spinal cord by RT-PCR. Vero cells exhibited CPE after inoculation by the virus, which was isolated from the brain, spinal cord and kidneys. TMUV-KPS54A61 could maintain itself for a prolonged time in the brain, spinal cord and liver; therefore, it could be the target organs of virus and the TMUV-KPS54A61 could be pathogenic in young chickens and BALB/c mice.