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KMID : 0359320000400010101
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Korean Journal of Veterinary Research
2000 Volume.40 No. 1 p.101 ~ p.109
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Isolation of duck hepatitis virus and it´s attenuation in chicken embryos
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Abstract
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Duck viral hepatitis is an acute, highly infectious viral disease of young dacklings aged from two days to three weeks. The significant lesion associated with the disease was enlarged liver including necrotic foci and numerous hemorrhagic spots.
We have isolated five strains of duck hepatitis virus (DHV) from field cases showing about 20% mortality with a sign of opisthotonos. When a-day-old ducklings were intramuscularly inoculated with one of the isolates, 92% of the birds were died within s days.
We attempted to develop an attenuated strain of duck hepatitis virus (DHV) using one of the isolates by serial chicken embryo passages. The propagation of DHV in chicken embrvos was carried 140 passages. The virus titer increased gradually from the 21^(st) through the 50^(th) passage, but there was no significant increase of virus titer in subsequent passages after then. Through the serial passages, the virulence of the virus for chicken embryos was gradually increased but decreased for ducklings. The pathogenicity of the virus for ducklings was preserved up to the 21^(st) passage but disappeared at the 50^(th) passage.
An attenuated Korean isolate which was passaged 140 times in chicken embryos gave good protection in ducklings against both challenge infection to a Korean virulent strain and to a DHV-DRL strain, a type 1 reference strain of DHV, which indicated that the Korean isolates could be classified as DHV type 1.
And the above results suggest that an attenuated Korean isolate can be used for developing a live DHV vaccine.
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