The etiology of sporadic bovine leukosis (SBL) is not known. Long-term monolayer cultures were made from calf (CLS), thymic (TLS) and skin (SLS) forms, and serological tests, electron microscopic observations and reverse transcriptase assays were employed for the detection of an etiological agent. Bovine leukosis virus (BLV) antigen and reverse transcriptase activities remained negative in cult...

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 s...

Bovine leukemia virus (BLV) infection, endemic in North American dairy herds, has production-limiting effects. A literature review of available papers published since 1995 concerning BLV transmission and its control was conducted. Although confirmed routes were reviewed (blood, natural breeding, utero, colostrum, milk), there is still a lack detailed information on other specific risks for (e.g...

Thirteen bovine leukemia virus- (BLV-) negative and 22 BLV-positive Holstein cows were immunized with J5 Escherichia coli bacterin at dry off, three weeks before calving, during the second week after calving, and three weeks after the third immunization. Serum was collected before the initial immunization, immediately before the third and fourth immunizations, and 21 days after the fourth immun...

Thirty colostrum-deprived calves from leukemia-free herds were foster nursed for 10 weeks on cows infected with bovine C-type virus (BLV) from multiple-case herds or on cows from leukemia-free herds. After weaning, the calves were raised in continuous contact with BLV-infected animals of approximately the same ages. Sera collected at 6 to 18 and 43 to 48 months of age were examined for the pres...

Peripheral blood lymphocytes from 14 cattle infected with the bovine leukemia virus (BLV) and 14 BLV-free cattle were examined by the membrane immunofluorescent antibody technique to detect surface immunoglobulin (S-Ig) and by the erythrocyte-antibody-complement (EAC) rosette test for the detection of complement receptors. Direct comparisons of the percentages of S-Ig-bearing cells and EAC rose...

MicroRNAs (miRNAs) are small RNAs that play a regulatory role in numerous and diverse eukaryotic cellular processes. Virus-encoded miRNAs have garnered much interest, although the functions of most remain to be deciphered. To date, readily detectable, evolutionarily conserved natural miRNAs have only been identified from viruses with DNA genomes. Combined with the fact that most miRNAs are gene...

Seroprevalence of bovine leukemia virus (BLV) infection was studied in replacement dairy heifers. Blood samples were collected from 80 pregnant heifers raised in 8 dairy farms in Saraburi province, the central part of Thailand and serum samples were tested for antibodies against BLV infection using commercially available ELISA test kits. The results revealed that 26 (32.5%) pregnant heifers wer...

The relationship of cull rate to age was investigated retrospectively in dairy cows with and without antibodies to bovine leukemia virus (BLV). Banked sera from eight annual herd tests on one 200-cow herd were tested for presence of BLV antibodies by agar-gel immunodiffusion using the Mr 51,000 glycoprotein antigen of BLV. Age-specific cull rates were computed for BLV-antibody-positive and anti...

To understand how the latest dominant bovine leukemia virus (BLV) strains were introduced and spread in the Miyazaki prefecture, we collected blood samples from 3 geographic areas (north, central and south) and carried out sequence analysis of the BLV env gene. Two genotypes, genotype I, and III, were identified and the majority of the strains belonged to genotype I (71/74). To clarify a route ...