• Korean Journal of Veterinary Service
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• v.44 no.1
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• pp.35-43
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• 2021

Rabbit infectious hemorrhagic fever has been reported in rabbits worldwide. The disease is also frequently reported on Korean rabbit farms, and the pathological study of 9 rabbits on such disease-occurring farms was attempted to identify the pathogen. Clinical signs were torticollis and ear ulceration. Most rabbit died with bloody nasal discharges. At necropsy, multiple hemorrhages and inflammation were observed in heart, lung, liver and uterus. The main histopathologic features were hemorrhagic suppurative meningoencephalitis, fibrinous bronchointerstitial pneumonia, bacteremia, liver cell necrosis, multifocal hemorrhages in kidney and disseminated intravascular coagulopathy. The viral VP60 gene of RHDV was identified by Reverse Transcriptase PCR. Pasteurella multocida organisms were cultured, identified by biochemical test and serotyped as A by multiplex capsular typing PCR. In conclusion, the fatal hemorrhagic disease was due to combined infection with both RHDV and P. multocida in rabbits. To our knowledge, this is the first case report about co-infection with both RHDV and P. multocida in rabbits in Korea.

• Journal of Microbiology and Biotechnology
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• v.25 no.11
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• pp.1960-1965
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• 2015

Rabbit hemorrhagic disease virus (RHDV) is highly contagious and often causes fatal disease that affects both wild and domestic rabbits of the species Oryctolagus cuniculus. A highly pathogenic RHDV variant (RHDVa) has been circulation in the Korean rabbit population since 2007 and has a devastating effect on the rabbit industry in Korea. A highly pathogenic RHDVa was isolated from naturally infected rabbits, and the gene encoding the VP60 protein was cloned into a baculovirus transfer vector and expressed in insect cells. The hemagglutination titer of the Sf-9 cell lysate infected with recombinant VP60 baculovirus was 131,072 units/50 μl and of the supernatant 4,096 units/50 μl. Guinea pigs immunized twice intramuscularly with a trial inactivated RHDVa vaccine containing recombinant VP60 contained 2,152 hemagglutination inhibition (HI) geometric mean titers. The 8-week-old white rabbits inoculated with one vaccine dose were challenged with a lethal RHDVa 21 days later and showed 100% survival rates. The recombinant VP60 protein expressed in a baculovirus system induced high HI titers in guinea pigs and rendered complete protection, which led to the development of a novel inactivated RHDVa vaccine.

• Korean Journal of Veterinary Research
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• v.29 no.4
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• pp.531-540
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• 1989

A new sudden death in rabbits appeared in China and Korea in 1984 and 1985, respectively, and was recognized to be an acute infectious disease caused by a virus. The disease was reported as a "new viral disease," and thereafter, a tentative name of "viral hemorrhagic disease", "hemorrhagic pneumonia" or "viral hemorrhagic pneumonia" has been described in the case reports. But authors had called the viral disease "rabbit viral hepatitis" due to picornavirus infection, because the principal lesion of the disease was an acute hepatitis. The purpose of this report is to describe the electron microscopic findings on the livers in experimentally infected rabbits. All the livers of the affected rabbits were shown to have degenerative changes of a type that is characteristic of acute hepatitis. In the liver cells, there were dilation of rER and mitochondria, vacuole formation of various sizes, and appearances of many virus-like particles in the vicinity of rER, granular bodies and crystalline arrays of viral particles in the cytoplasm with necrotic changes of the nucleus. Clusters of virus-like particles and viral crystals appeared in the cytoplasm of sinusoid endothelial cells and Kupffer's cells with morphological changes of organelles. Also viral crystals were demonstrated in the cytoplasm of macrophages among the liver cells. On the whole, the liver cells had many virus-like particles and a few crystalline arrays of viral particles. Therefore, this implies that the liver cells are the main site of the viral replication in inducing the viremia. It was concluded that the liver was the primary target organ of this viral disease, and the pathological and the ultrastructural evidence suggest that the virus may be belong to genus enterovirus.

• Korean Journal of Veterinary Research
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• v.30 no.1
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• pp.65-71
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• 1990

Rabbits were experimentally infected with rabbit hemorrhagic disease virs and the viral pathogenicity, hemagglutinability, and the effect of physicochemical factors were studied. The experimental results were summariaed as follows: 1. Mean rectal temperature of 11 infected rabbits was $40.0{\pm}0.47^{\circ}C$ prior to the virus inoculation, and $39.9{\pm}0.75^{\circ}C$ after 12hrs., $40.2{\pm}0.65^{\circ}C$ after 24hrs., $40.1{\pm}0.77^{\circ}C$ after 36hurs, and $40.6{\pm}0.56^{\circ}C$ just before the death. 2. Mean death time of infected rabbits was $40.3{\pm}22.0$ honrs and its range was 24 to 93 hours. 3. O, B, AB and A type of human erythrocytes were shown their HA in the order, but rabbit and chicken erythrocytes were not hemagglutinated by the virus. 4. In the hemagglutination, less than 0.25 per cent of a final concentration of erythrocytes and 0.2 per cent of BSA in PBS resulted in the best hemagglutination. Phosphate concentration in a range of 0.01M to 0.10M in PBS was not influenced on the hemagglutination reaction, and its pH 7.0 resulted in a better HA. 5. The hemagglutinating titers, in log 2 scale, of organs and tissues of the virus infected rabbits were $9.3{\pm}3.8$ (liver), $9.1{\pm}3.9$ (blood), $6.2{\pm}2.6$ (spleen) and $5.0{\pm}2.5$ (kidney). 6. The physicochemical factors such as heating ($50^{\circ}C$, 10 min.), trypsin treatment (0.05 pre cent, 5 min.), acid treatment (pH 3.0, 20 min.) and ether extraction (3 times) were not affective to the stability of virus and viral HA activities.

• Korean Journal of Veterinary Research
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• v.49 no.3
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• pp.207-213
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• 2009

Rabbit hemorrhagic disease (RHD) is caused by RHD virus (RHDV) and is one of the most fatal diseases of rabbits. Acute death of rabbits occurred in a farm located in the Gyeonggi province of South Korea. The virus was isolated and confirmed as RHDV based on reverse transcription polymerase chain reaction and hemagglutination assay (HA), and the isolate was designated as KV0801. The nucleotide sequence of the complete VP60 gene of KV0801 was determined and the corresponding amino acid sequence was deduced. Molecular analysis showed that the KV0801 isolate can be classified as a pandemic antigenic variant strain, RHDVa. The VP60 nucleotide sequence and deduced amino acid homology between KV0801 and other Korean isolate, RHF89, which was isolated in 1988, were 92.1 and 94.3%, respectively. The pathogenicity of the KV0801 isolate at an HA titer ranging from 16,384 to 0.16 HA units was evaluated in five-month-old SFP rabbits. The rabbits inoculated with KV0801 isolate containing more than 1.63 HA units died within six days of inoculation. These results suggest that a highly pathogenic RHDVa is circulating in the rabbit populations of Korea.

• Korean Journal of Veterinary Research
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• v.30 no.1
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• pp.73-78
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• 1990

Hematological and blood chemical changes of rabbits infected with rabbit hemorrhagic disease virus were studied and the results were summarized as follows: 1. Total leukocyte count ($2,410{\pm}1,076/{\mu}l$), lymphocyte count ($1,582{\pm}632.5{\mu}l$) and heterophil count ($705{\pm}411.1{\mu}l$) were significantly decreased after 24 hours of the infection (p<0.01). However, no significant changes were observed in monocyte, eosinophil and basophil numbers. 2. A significant increase of aspartate aminotransferase (96IU/L), alanine aminotransferase (96IU/L) and alkaline phosphatase ($401.1{\pm}131.8IU/L$) was observed (p<0.01). 3. A moderate increase of BUN ($26.9{\pm}3.6mg/100ml$) and creatinine ($3.2{\pm}1.9mg/100ml$) was observed (p<0.05). 4. No significant changes of r-GTP, thymol turbidity, glucose, cholesterol, albumin, total serum protein, fibrinogen were observed.

• Korean Journal of Veterinary Research
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• v.53 no.1
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• pp.11-17
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• 2013

In this study, to understand the pathogenesis of new rabbit hemorrhagic disease virus (RHDVa) serotype, we carried out to administrate RHDVa to rabbits, and to examine sequential electron microscopic changes and relationship between pathogenesis and apoptosis. TUNEL-positive cells began to be observed from 24 hours after inoculation (HAI) and the number of positive cells was slightly increased with the course of time. Whereas marked increase of positive cells was seen in the liver from the rabbits died acutely. Typical viral particles with cup-like projections and a diameter of 30~40 nm were detected in homogenized liver samples and tissues at 36 and 48, and 48 HAI, respectively. Ultrastructurally, glycogen deposition was observed from the first stage of hepatocellular degeneration by RHDVa infection and then, swelling and disruption of cristae of mitochondria by viral particles, swelling of smooth endoplasmic reticulum, vacuoles and vesicles were detected. Condensation, margination and fragmentation of chromatin were observed in degenerative hepatocytes at 36 and 48 HAI, indicating apoptotic bodies. These data offer that hepatocytic apoptosis by RHDV infection could be closely related with mitochondrial impairment in the hepatocytes.

• Korean Journal of Veterinary Research
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• v.52 no.2
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• pp.125-131
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• 2012

Rabbit hemorrhagic disease is a highly acute and fatal viral disease caused by rabbit hemorrhagic disease virus (RHDV). Since first outbreak in Korea 1987, RHDV has been continually affected in the country, but the pattern of outbreak seem to be changed. In this study, to understand the pathogenesis of the new RHDVa serotype, we therefore carried out to inoculate RHDVa to rabbits, and to examine the sequential histopathologic changes and viral distribution. Macroscopically, various sized dark red or white spots or appearance were observed in the liver, lung, kidney uterus and ureter. In euhanized rabbits, significant pathologic findings such as infiltration of heterophils and mononuclear cells were observed at 24 hours after inoculation (HAI), and these were sequentially extended periportal to centrilobular area. However, in dead rabbits, severe hepatic degeneration and/or necrosis with relatively weak inflammatory responses were observed. RHDV antigens began to detect in liver, spleen, and lung from 12 HAI by PCR. Immunohistochemically, RHDV positive cells were seen in only liver from 24 HAI, and the degree of immunogen reactivity was stronger in dead rabbits than in euthanized ones. In conclusion, RHDVa caused the subacute or chronic infection accompanying low mortality and moderate to severe inflammatory reaction in rabbits, suggesting the possibility that RHD could become endemic.

• Korean Journal of Veterinary Pathology
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• v.5 no.2
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• pp.57-62
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• 2001

Recently various molecular diagnostic techniques have been used to identify rabbit hemorrhagic disease virus (RHDV), a causative agent responsible for acute hepatitis and disseminated intravascular coagulation in rabbit. But they were hard to perform and time consuming. To detect RHDV in a rapid and easy way, we developed biotinylated oligonucleotide probe within ORF 1 region encoding the polyprotein of RHDV in formalin-fixed and paraffin-embedded tissues from various tissues of 20 rabbits naturally infected with RHDV, Our in situ hybridization (ISH) was quickly carried out within two hours by MicroProbe capillary action system. The ISH produced a positive reaction in liver, kidney and lung. In conclusion, ISH with a biotintlated oligonucleotide probe provided a useful diagnostic method for detecting RHDV.

• Korean Journal of Veterinary Research
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• v.39 no.2
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• pp.359-364
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• 1999

We investigated the pathological changes in young rabbits which were experimentally infected with rabbit hemorrhagic disease virus (RHDV). Experimental infection of RHDV was carried out in both thymectomized and non-thymectomized young immature rabbits and adult rabbits. None of young rabbits infected with RHDV died during the experiment. Histologically, single or focal hepatocellular degeneration and necrosis with mild lymphocyte infiltration were observed in the rabbits killed at 30 hours and 5 days PI. Lymphocyte infiltration was more severe at 5 days PI than at 30 hours PI. RHDV antigens were mainly detected in the degenerating hepatocytes adjacent to the infiltrated lymphocytes at 30 hours PI and 5 days PI. In electron microscopical observation, infiltrated lymphocytes in the lesions had large nuclei without cytoplasmic granules and interdigitated with adjacent hepatocytes. It is assumed that infiltrated lymphocytes in hepatic lesions in RHDV infected young rabbits are T-lymphocytes and originate from peripheral lymphoid organs or tissues rather than from thymus.