• 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.

• 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.

• 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.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 Veterinary Research
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• v.55 no.1
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• pp.53-56
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• 2015

Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis. This study was conducted to clarify the molecular characteristics of BLVs obtained from a specific region in Korea. Proviral BLVs were detected in anti-BLV antibody-positive blood samples by PCR. Env and gag fragments were sequenced and compared to previously published reference sequences. Analysis of the env gene sequence revealed that the YI strain was highly similar to genotype 1, including United States and Japanese strains. The gag gene sequence had the highest degree of similarity with a Japanese strain.

• Korean Journal of Veterinary Research
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• v.45 no.2
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• pp.239-244
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• 2005

Hematologic investigations were made on the blood samples taken from bovine leukemia virus (BLV)-seropositive Holstein-Friesian cattle in Korea, and their absolute lymphocyte count was compared with that of BLV-seronegative cattle. The incidence of persistent lymphocytosis (PL) was also determined. The normal bovine lymphocyte count was established on the basis of studies of 656 blood samples taken three times from 297 seronegative animals aged from 0~6 months to over 5 years at 5~6-month intervals. The data were examined according to 7 age groups of samples placed into their respective age groups. A peak in average total count was reached at 6~12 months ($5.36{\times}10^3/{\mu}l$) and thereafter the count declined continuously until over 5 years ($3.17{\times}10^3/{\mu}l$). From the results, 99.74 percent limits were calculated, and the upper limit of the range was chosen as the cutoff point for lymphocytosis. A PL was defined as a lymphocyte count that exceeded the above 99.74 percent limits and persisted over an interval of at least three months. The criterion for PL was applied to classifying 515 blood samples obtained four times from 189 seropositive animals without clinical signs at 5~7-month intervals. It was found that 54 (28.5%) of seropositive animals were with PL; cattle with PL were in age groups of 2~3 years to over 5 years.

• Proceedings of the Korean Society of Veterinary Pathology Conference
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• 2003.10a
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• pp.50-50
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• 2003

Enzootic bovine leukosis(EBL) is chronic disease caused by bovine leukemia virus(BLV), retroviridae. The characteristic feature of this disease is proliferation of lymphocytes in circulating blood or lymphoid tissues. Because EBL concern lymphocytes, immunological disorder or alteration in the lymphocyte subpopulation is suggested. In this study, we investigated the changes of the lymphocyte subpopulation in the circulating blood of Korean native cattle infected with bovine leukemia virus. (omitted)

• Korean Journal of Veterinary Research
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• v.45 no.3
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• pp.391-398
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• 2005

Several studies have been performed on the bovine leukemia since bovine leukemia virus (BLV) had been detected in 1982 in Korea. We have conducted histopathological study on the bovine lymphoma caused by BLV because only limited results were reported on the pathological characterization of lymphoma. Lymphoma tissues were obtained from cattle necropsied and slaughtered during a designated period. Lymphoma was classified histopathologically according to the National Cancer Institute Working Formulation. Leukotic tissues consisted of fairly uniform sheets of closely packed medium to large lymphocytes without any architectural arrangement in all 30 cases. Twenty five cases belong to diffuse large cell type, while three cases were diffuse mixed cell type, and two cases were immunoblastic large cell type among 30 cases. Follicular type lymphoma was not detected in this study. The mitotic index of tumor cells showed average 2.5 in the field of 400X. Nuclear cleavage was detected in 53% of cases. Multi-nucleated cells were detected among tumor cells in 30% of lymphoma cases. In conclusion, the most common morphologic cell type of bovine lymphoma in Korea was a diffuse large cell type with multinucleated cells and nuclear cleavages.

• 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.

• 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.