• Korean Journal of Veterinary Research
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• v.40 no.1
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• pp.110-116
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• 2000

Duck viral hepatitis is an acutic, highly infectious viral disease of young ducklings. The most practical means for controlling duck viral hepatitis is the vaccination of ducklings or of a breeding stock. We attempted to develop a vaccine strain of duck hepatitis virus (DHV) using a Korean isolate by serial chicken embryo passages. The propagation of DHV in chicken embryos was carried 140 passages. After the $50^{th}$ passage, of which the virus was non-pathogenic for ducklings, approximately every $20^{th}$ passage of the virus was tested for vaccinal efficacy. Both the $70^{th}$ and $90^{th}$ passage of the virus gave good protection against challenge infection to a DHV-DRL reference strain(type 1) and a virulent Korean isolate. The $110^{th}$, $125^{th}$ and $140^{th}$ passage of the virus were less protective than the $70^{th}$ and $90^{th}$ passage, which means that more than $110^{th}$ passage may lead to over-attenuation of the virus. Ducklings vaccinated with the chicken-embryo-adapted virus by oral, intramuscular or eye drop administration showed earlier resistance to challenge infection from 3 to 7 days postvaccination. Of the above methods, ducklings vaccinated intramuscularly presented the most rapid resistance against challenge. The minimum immune dose of the chicken-embryo-adapted virus in ducklings was also studied. Ducklings inoculated with a dose of $10^{2.0}\;ELD_{50}$ and below were not fully protected against challenge with a virulent DHV, showing a protection rate of 67% to 73%, but ducklings inoculated with a dose of $10^{3.0}\;ELD_{50}$ and over were completely protected. The virus yield of the chicken-embryo-adapted DHV was examined at 24hrs and 48hrs of the incubation time in the allantoic fluid, embryo head and embryo minus head of the embryonating egg. In all three components, the titer of the virus was higher at 48 hours than that at 24 hours after incubation. And the titer of the virus was higher in the embryo minus head, embryo head and the allantoic fluid, in order. Field trials for evaluating the efficacy of the attenuated DHV as a live vaccine were done in duck farms with about 25% mortality of flocks resulting from duck viral hepatitis. After the use of the experimental vaccine, the mortality due to duck viral hepatitis was dramatically reduced in the farms. These results indicated that the attenuated DHV using a Korean isolate could be a good candidate as a live vaccine strain of DHV in Korea.

• Korean Journal of Veterinary Research
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• v.40 no.1
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• pp.101-109
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• 2000

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 5 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 embryos 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.

• Korean Journal of Veterinary Research
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• v.25 no.2
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• pp.171-174
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• 1985

An outbreak of duck virus hepatitis was confirmed for the first time in Korea from ducklings having up to 40~65% mortality in less than 15-day-old ducklings of two farms located in the vicinity of Kwangju city. The infected ducks showed sudden death and opisthotonus position. The predominant gross lesions were found in the liver, showing enlargement and petechial or ecchymotic hemorrhages. The microscopic findings were consisted of fatty changes and necrosis of the hepatic cells, and proliferation of the bile duct epithelium. The presence of the virus was detected by electron microscopy of the sera and livers of infected ducks. The duck embryo and the ducks inoculated with the liver materials from the infected ducks showed the same lesions with those of the naturally infected ducks.

• Asian-Australasian Journal of Animal Sciences
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• v.6 no.3
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• pp.331-337
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• 1993

In order to understand the effect of duck hepatitis B virus (DHBV) on the economic performance of ducks, Three groups (DHBV congenitally infected, experimentally infected and DHBV negative) Brown Tsaiya ducks (Anas platyrhyncha) were used for experimental animals. Artificial insemination and pedigree hatching were applied in the propagation of ducklings, and the efficiency of vertical transmission and experimental infection was analyzed through the detection of DHBV DNA in the sera of 8-week-old offspring. The observation of the records of the first year indicated that the persistent infection had no significant effects on the performance of ducks, except the egg number of survival ducks up to 40 week of age. Thus DHBV infection did not appear to give ill effects to the economic performance of ducks in first laying year. A higher infection rate (85.3%) was obtained in congenital transmission than that (75.5%) of experimental infection. Both modes of infection did not reach 100% infectious rate, although some ducks developed transient viraemia in a tracing of DHBV DNA for 24 weeks to 11 challenged ducklings.

• Korean Journal of Veterinary Pathology
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• v.5 no.2
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• pp.43-48
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• 2001

Ducklings collected from three farms, having history of rapid onset and spread of nerve signs including kick spasmodically with legs and opisthotonos, were pathologically, barteriologically, virologically examined. Grossly, multiple petechial to ecchymotic hemorrhages were detected in the swollen liver. Histopathologically, diffuse coagulative necrosis of hepatocytes was characteristic in acute cases. Chronic cases revealed marked bile duct hyperplasia rather than hepatocyte necrosis. Some of these cases exhibited multiple granulomas consisting of macrophages, heterophil, fibrin and necrotic cell debri. Filtered homogenate of livers sampled from ducklings caused embryo death with marked hemorrhage and swollen of liver after inoculation into chorioallantoic membrane. Three strains of Salmonella app.,S montevideo, S hadar, and S give, which were biochemically and serologically identified, weir isolated from ducklings of three farms, respectively. From these results, these ducklings were concurrently infected with duck hepatitis virus and Salmonella spp.

• Korean Journal of Poultry Science
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• v.38 no.1
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• pp.13-19
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• 2011

In January 2010, high mortalities of ducklings occurred in two adjacent farms. Ducklings in farm A showed neurologic signs including paddling, opisthotonus and lameness, but ducklings from farm B had no specific clinical signs. At post mortem, diffused hemorrhagic spots in the liver and hemorrhages in the small intestine were observed in ducklings from farm A, and ducklings from farm B had only proventricular ulceration. Microscopically, multiple necrosis of hepatocytes, hyperplasia of the bile ducts, hemorrhages, infiltration of lymphocytes and bacterial colonies were commonly observed in the liver of ducklings from both farms. Also, type A and C duck hepatitis virus (DHV) were isolated from farm A and farm B, respectively and Salmonella typhimurium was commonly isolated and identified serologically and biochemically. To our knowledge, this is the first report about the co-infection of DHV and Salmonella typhimurium in ducklings, and co-circulation of type A and C duck hepatitis viruses in Korea.

• 대한예방의학회:학술대회논문집
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• 2000.10a
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• pp.116-117
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• 2000

• Korean Journal of Veterinary Service
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• v.34 no.1
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• pp.19-29
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• 2011

Prevalence of major legal communicable diseases in chickens and ducks, which had occurred in Jeonbuk province from year 2004 to 2008. Total 283 farms 1,419,244 chickens and ducks have been affected by avian diseases. Specifically, fowl typhoid (FT) occurred in 92 farms 416,600 chickens, Marek's disease (MD) in 45 farms 145,563, duck virus hepatitis (DVH) in 31 farms 199,200, infectious bursal disease (IBD) in 27 farms 113,220, infectious bronchitis (IB) in 27 farms 280,300, low pathogenic avian influenza (LPAI) in 26 farms 78,495, avian mycoplasmosis in 16 farms 103,774, Newcastle disease (ND) occurred in 11 farms 61,052, avian encephalomyelitis (AE) in 7 farms 21,000, Pullorum disease (PD) occurred in 1 farm 40. According to total analysis about major legal communicable diseases, 1 species of first-class legal communicable diseases have occurred, 3 species of second-class and 6 species of third-class all adding up to 10 species. In the first-class diseases, Newcastle disease have occurred. Pullorum and fowl typhoid, duck virus hepatitis in the second-class have occurred and as third-class diseases, Marek's disease, Infectious bursal disease, Infectious bronchitis, avian mycoplasmosis, avian encephalomyelitis, low pathogenic avian influenza have occurred.

• Korean Journal of Veterinary Service
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• v.20 no.4
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• pp.323-329
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• 1997

An outbreak of duck septicemia caused by Pasteurella anatipestifer was studied in Chonnam province. The outbreaks of duck septicemia has become an economically important disease in duck farm. The present study undertaken to identify the etiological agent of duck septicemia and to evaluate the efficacy of bacterin against P anatipestifer in Chonnam province during period from May to December 1996. The results obtained were as follows ; 1. The distribution of etiological agents from collected 328 duck samples were Pasteurella anatipestifer(57%), Escherichia coli(21%), duck viral hepatitis virus(4%), Salmonella sp(1%) and others (10%). 2. The agglutination titers of autogenous vaccine were increased after End vaccination and reached highest at 5-6 weeks post inoculation at the titers of 6.0-4.0.

• Journal of The Korean Society of Agricultural Engineers
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• v.63 no.1
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• pp.37-48
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• 2021

The automatic-spreader of bedding materials was developed to reduce labor cost, and to achieve successful biosecurity in duck houses. Algorithm of the device was designed to realize a concept of the automatic unmanned operation including entire processes such as loading and spreading of the bedding materials. From the field measurement, the relationship between the expected water content reduction and weight of bedding materials per unit area according to the operation condition of the devices was induced. In the case of the measurement of particulate matters during the process of spreading works, the results of using both conventional manual-spreader and automatic-spreader were exceeded the allowable limit of inhalable and respirable dust, respectively. But, workers using automatic-spreader could be free from harmful aero-condition because they did not stay inside the facility during the spreading works. In addition, from the Duck hepatitis virus PCR test, influence on pulmonary tissue of the duck was not found. It could be expected that the development of the automatic-spreader of bedding materials for duck house can contribute to the advancement of duck breeding facilities.