• Journal of Veterinary Clinics
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• v.20 no.2
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• pp.172-176
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• 2003

As a baseline study for the establishment of bovine leukemia virus(BLV)-free herd in Korea, the prevalence of anti-BLV antibody was determined in the present study. Sera from Korean native cows of 8 provinces and from dairy cattle of 9 provinces were subjected to enzyme-linked immunosorbent assay. Anti-BLV antibodies were positive in two (0.14%) of 1,413 Korean native cows. In contrast. 54.2% of 2,415 dairy cows were positive for anti-BLV antibodies, and their seropositive herd rate was 86.8%. And no differences were found in the sero-positive rates with age. The results indicate that the BLV infection rate has been increased continuously in Korea and that the establishment of BLV-free herd is imminent.

• The Journal of Korean Society of Virology
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• v.27 no.2
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• pp.217-225
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• 1997

PCR amplication using the primers for gag, pol and env genes in BLV (bovine leukemia virus) proviral DNA and syncytium assay were carried out for the Korean native goats experimentally infected with bovine leukemia virus to investigate pathogenesis of BLV in the goats, and to establish a model animal for BLV infection. The oligonucleotide primers used in PCR revealed very high specificity. The minimal amount of FLK-BLV cellular chromosomal DNA to detect the integrated BLV proviral DNA was 10 ng. The peripheral blood lymphocytes from the goat infected with BLV were examined at regular intervals by PCR amplification and syncytium assay. Pol or gag genes were detected in none of three infected goats at the 1st week post-infection (p.i.). At the 4th week p.i., one of three goats showed the amplified gag gene. Thereafter detection rates for the genes were increased, indicating that the BLV proviral genes were integrated in all of the lymphocytes from three goats, at the 16th weeks p.i., when it was evident in syncytium assay that the lymphocytes from all of three goats were infested with infective BLV. Investigating the tissues from the necropsied goats at the 8th month p.i., the amplified BLV proviral genes and infective BLV were detected in all of the peripheral lymphocytes from three infected-goats. Among various tissues examined, the amplified BLV proviral genes were observed in spleen and superficial cervical, mandibular and retropharyngeal lymph nodes, and the infective BLV, in superficial cervical and mandibular lymph nodes. It was assumed that the Korean native goat was quite susceptible to BLV infection, indicating that the goat could be a good model animal for BLV.

• Korean Journal of Veterinary Service
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• v.35 no.4
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• pp.333-337
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• 2012

This study was carried out to investigate the prevalence of bovine leukemia virus (BLV) infection and to compare the results of enzyme-linked immunosorbent assay (ELISA) and nested polymerase chain reaction (nPCR) in dairy farms in northern Gyeonggi province from August through December 2011. A total of 625 dairy cattle from 14 dairy farms were tested for antibodies against BLV using commercially available ELISA test kit. The overall seroprevalence of BLV infection was 76.3%. The seroprevalence of diary cattle according to age was the highest at 61~72 months (88.0%, P<0.001). Two hundred fifty one dairy cattle from 7 diary farms were tested ELISA and nPCR. The kappa value of BLV between ELISA and nPCR was 0.765. The results indicate that BLV infection spread widely in dairy farms and the nPCR is rapid method for the early detection of BLV infection.

• Korean Journal of Veterinary Service
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• v.15 no.1
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• pp.51-57
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• 1992

A serological survey was carried out for the detection of antibody of Bovine Leukemia Virus (BLV) in nothern parts of Chung Buk area. The results were summarized as followed. 1. The overall positive rate was revealed as high as 15% with 48 positive cases out of 319 heads examined. 2. According to age, cattle of 4 to 7 ages showed relatively higher positive rate of 15% than other ages. 3. Seasonal differences of positive rate were not recognized. 4. BLV antibody titer of scales of cattles that from 5 to 15 heads farm were the highest. 5. With the result of blood test that of BLV positive cattle, the number of WBC was slightly Increased, but other records were normal.

• Korean Journal of Agricultural Science
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• v.27 no.2
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• pp.101-106
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• 2000

A total of 181 Holstein and 73 Korean cattle were used to investigate the association of bovine leukemia virus (BLV) resistance stains with major economic traits. The frequencies of BLV resistance strain with 91bp PCR products were 60.0% and 40.0% in Holsten and Korean cattle, respectively. The association of BLV resistance and susceptibility strains with 305-d milk and 305-d milk fat yields were not significant(P>0.05) in Holstein cattle. Body weights at birth, 6-mon, and 120-mon of age were not significantly associated with the BLV resistance and susceptibility strains of Holstein and Korean cattle. It could be concluded that the alleletypers of BLV resistance were not associated with major economic traits in Holstein and Korean cattle.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.6
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• pp.879-883
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• 2005

The integral relationship between the occurrence of lymphocyte nuclear pockets (LNPs) and BLV-infection was examined in Holstein-Friesian dairy cattle in Korea. Transmission electron microscope (TEM) was used to detect LNP in peripheral blood lymphocytes. Morphologically, the membranes of LNP were composed of two layers of double nuclear membrane. The full thickness of LNP membranes including inner and outer nuclear membrane was 60 to 70 nm. LNP prevalence was different according to the bovine leukemia virus (BLV) infection status; in BLV-seropositive cattle, LNP prevalence was 48.4% and in BLV-seronegative cattle prevalence was 5.9%. Moreover, even in seropositive animals, leukemic group was the highest at 70% positive among the groups, followed by suspect group (42.4%) and aleukemic group (23.1%). Consequently, the numbers of LNP were increased in proportion to increase of the numbers of leukocytes among BLV-seropositive cattle. The numbers of LNP per lymphocyte were increased in BLVseropositive cattle compared with seronegative cattle. The mean numbers of LNP per 100-lymphocytes were 0.35, 0.77, 1.64 and 4.7 in BLV-seronegative, BLV-seropositive aleukemic, suspect and leukemic groups, respectively. Thus, it is reasonable that LNP test can be used as the one of the diagnostic criteria of BLV infection.

• Korean Journal of Veterinary Research
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• v.26 no.1
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• pp.61-68
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• 1986

This paper described the distribution and transmissibility of BLV(bovine leukemia virus), the relationship between antibodies against BLV and lymphocyte count in 313 dairy cattle from 36 herds, the clinical signs and hematological findings of 2 lymphosarcomatous cattle in the northern area of Kyungpook. Eighty three (26.5%) of 313 cattle from 36 herds were positive for BLV antibodies and 19 (52.8%) of 36 herds were infected with BLV by the immunodiffusion test with BLV-gp antigen. The rate of BLV infection in cattle varied from 9.5 to 87.5% in 19 positive herds, it was higher in herds pastured during summer and included lymphosarcomatous onset than the other and also higher with the age. Eight (88.9%) out of 9 cattle which showed persistent lymphocytosis by the hematological test were positive for BLV antibodies. After 5 to 14 months, 13 (31.0%) of 42 cattle being negative for BLV antibodies in the positive herds converted into positive. Two lymphosarcomatous cattle were identified to be EBL (enzootic bovine leukemia) by the clinical sign, hematological examination and serological test.

• Journal of Veterinary Clinics
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• v.27 no.4
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• pp.402-406
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• 2010

Bovine leukemia virus (BLV) is a delta-retrovirus which causes chronic lymphocytosis in cattle. BLV infections have been divided into two groups such as enzootic bovine leukosis (EBL) and sporadic bovine leukosis (SBL) according to the clinical symptoms in infected cattle. The conventional detection method of BLV was hematological procedure which is determining lymphocytosis in the suspected animals. Recently several sensitive methods were developed to detect antibody to BLV and nucleic acid of the BLV from infected cattle. In this study we have compared the difference of positive rates between agar gel immunodiffusion (AGID) and enzyme linked immunosorbent assay (ELISA) which are using for BLV antibody detection methods. The positive detection rate of ELISA test was 7.4% greater than the positive rate of AGID. The discrepancy of the positive rate between ELISA and AGID were showed in the group of age over one year old to under three year old group. The result from each test agreed very well in the group of over 5 year old cattles. The serological test is very useful method to select the infected cattle for the eradication or control of the disease in the infected herd. But it has a limit by interference of the maternal antibody from the cow of under 6 month old. This study shows that 16.2% of these ages group showed BLV gene positive by polymerase chain reaction (PCR) method. The result suggests that ELISA test need to be used with PCR to clarify misinterpretation of positive animals by antibody response due to the natural infection from maternally derived antibody in calves of under 6 months old.

• Applied Microscopy
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• v.35 no.1
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• pp.23-30
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• 2005

Many studies have been performed on the bovine leukemia virus (BLV) since bovine leukosis had been reported in 1968 in Korea. However, there was no report on the ultrastructural examination of BLV. An attempt to detect C-type viral particles in the cultured peripheral blood lymphocytes of Holstein-Friesian dairy cattle, was made to determine whether in vitro viral expression might be used as a reliable method to identify the cow which is likely to transmit BLV. In transmission electron microscopic (TEM) examination, the virus particles were found predominantly outside of the lymphocytes even though a few particles were also observed within the membrane bound cytoplasmic vacuoles. All of them were C-type particles consisting of a central, electron-dense core separated by a clear area from a limiting envelope with a unit membrane structure. Virus particles were easily detected in the lymphocyte which was cultured with medium supplemented with either T-lymphocyte mitogen (conconavalin A) or B-lymphocyte mitogen (lipopolysaccharide). Identical viral particles, although fewer, were also consistently present in the lymphocytes cultured with medium which was containing foetal bovine serum (FBS) only and which was containing neither FBS or mitogen. By contrast, no virus particle was detected in extensive examination of lymphocytes before culture. In conclusion, the BLV cultivation and detection methods established in this study could be used as a tool to identify and eliminate the cattle which can transmit the BLV.

• Korean Journal of Veterinary Research
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• v.30 no.3
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• pp.343-348
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• 1990

Total 51 calves born from both 28 seropositive and 23 seronegative dams were subjected to study both prenatal and postnatal infections of bovine leukemia virus (BLV), and the duration of passive colostral antibody by means of immunodiffusion (ID) test. All calves were tested for precolostral and postcolostral periods by 16 months of age. The results were as follows: 1. Of 28 precolostral sera of the calves born from infected dams, one appeared positive, indicating in utero BLV infection from the dam. 2. BLV-antibody test for the postcolostral sera of the calves born from seropositive or seronegative dams showed that the colostral antibody of the calves disappeared from 2 to 6 months of age, and the increase of the number of seropositive calves initiated from 3 to 4 months of age indicated postnatal infection.