Bovine leukemia virus detection and dynamics following experimental inoculation

Hutchinson, Holden C.; Norby, Bo; Droscha, Casey J.; Sordillo, Lorraine M.; Coussens, Paul M.; Bartlett, Paul C.

doi:10.1016/j.rvsc.2020.09.026

Cited by 15 publications

(19 citation statements)

References 26 publications

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“…This strategy involves periodic screening through use of ELISA, PCR-DB, and real-time PCR followed by segregation of all positive cases and of animals that exhibit high proviral load (more than three BLV copies/100 cells) at intervals of several months or a few years [11,88,182]. Additionally, the culling of older cows with high whole blood and lymphocyte counts helps to control BLV infection and is considered the cheapest screening method as it avoids the need for further testing [215,216].…”

Section: Strategies For the Control Of Blv Infectionmentioning

confidence: 99%

Bovine Leukaemia Virus: Current Epidemiological Circumstance and Future Prospective

Marawan

Alouffi

Tokhy

et al. 2021

Viruses

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Bovine leukaemia virus (BLV) is a deltaretrovirus that is closely related to human T-cell leukaemia virus types 1 and 2 (HTLV-1 and -2). It causes enzootic bovine leukosis (EBL), which is the most important neoplastic disease in cattle. Most BLV-infected cattle are asymptomatic, which potentiates extremely high shedding rates of the virus in many cattle populations. Approximately 30% of them show persistent lymphocytosis that has various clinical outcomes; only a small proportion of animals (less than 5%) exhibit signs of EBL. BLV causes major economic losses in the cattle industry, especially in dairy farms. Direct costs are due to a decrease in animal productivity and in cow longevity; indirect costs are caused by restrictions that are placed on the import of animals and animal products from infected areas. Most European regions have implemented an efficient eradication programme, yet BLV prevalence remains high worldwide. Control of the disease is not feasible because there is no effective vaccine against it. Therefore, detection and early diagnosis of the disease are essential in order to diminish its spreading and the economic losses it causes. This review comprises an overview of bovine leukosis, which highlights the epidemiology of the disease, diagnostic tests that are used and effective control strategies.

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Section: Strategies For the Control Of Blv Infectionmentioning

confidence: 99%

Bovine Leukaemia Virus: Current Epidemiological Circumstance and Future Prospective

Marawan

Alouffi

Tokhy

et al. 2021

Viruses

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“…While the range of the difference between first and last observation was −38,200 to 72,000 copies per 100,000 cells, the interquartile range was smaller and ranged from −300 to 14,600 copies per 100,000 cells ( Figure 4 d). Because it has been suggested that proviral load undulates around a relatively steady state [ 27 , 31 , 32 , 35 ], the PVL amplitude was calculated. The mean maximum change in PVL was 19,200 copies per 100,000 cells (median: 12,900; range: 0 to 115,600 copies per 100,000 cells; Figure 4 f).…”

Section: Resultsmentioning

confidence: 99%

“…Absolute fluctuations averaged 19,200 proviral copies per 100,000 cells. In an experimental infection study, we observed that PVL typically stabilized, with minor fluctuations after an initial peak following infection [ 32 ]. Thus, it is plausible that the observed variation is just normal variation around a relatively consistent proviral load.…”

Section: Discussionmentioning

confidence: 99%

“…Recently, it has been suggested that the relative level of PVL (high versus low) is established shortly after infection and is stable over time, with minor fluctuations in PVL observed [ 27 , 31 ]. In an experimental infection conducted by our research team, the average peak in PVL was observed 45 days post-inoculation followed by a decline or plateau to a relatively steady state until 147 days post-inoculation in a majority of the inoculated steers [ 32 ].…”

Section: Introductionmentioning

confidence: 99%

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Diagnostic Measures of Disease Progression in Cattle Following Natural Infection with Bovine Leukemia Virus

et al. 2021

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This study describes the longitudinal changes in bovine leukemia virus (BLV) ELISA antibodies, proviral load (PVL), and blood lymphocyte counts (LC) observed over a 2.5-year period in naturally infected cattle. The dataset utilized was from a BLV intervention field trial on three Midwestern dairy herds. Our analysis showed ELISA false negatives were more likely to occur in cattle with low PVL and normal LC. On average, negligible changes in LC were observed during six-month intervals. Periods of lymphocytosis, defined as >10,000 lymphocytes per uL of blood, were observed in 31.5% (68/216) of BLV test-positive cattle. In BLV test-positive cows, an average increase of 2900 to 3100 proviral copies per 100,000 cells was observed during each subsequent six-month sampling interval. The difference between the minimum and maximum PVL observed for an ELISA-positive cow with 3 or more observations ranged from 0 to 115,600 copies per 100,000 cells (median: 12,900; mean: 19,200). Therefore, following the identification of ELISA-positive cattle and the assessment of PVL and LC, subsequent semiannual tests to assess disease progression may not be needed. Further work is needed to determine how available diagnostic tests can be optimized to design cost-effective testing schemes for BLV control programs.

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“…Quantitative PCR (qPCR) allows for the relative and simultaneous quantification of provirus and host DNA with a high degree of specificity and sensitivity when used with TaqMan ® fluorophores. Our group developed the SS1 BLV proviral load qPCR multiplex assay (CentralStar Cooperative, Lansing, MI, USA) consisting of three TaqMan™ primer/probe assays that detect the BLV pol gene, bovine β-Actin , and an internal amplification control [ 17 , 18 , 19 ]. Through qPCR calibration using digital droplet PCR (ddPCR) normalized DNA standards, the SS1 assay has 100% specificity and sensitivity down to a limit of detection of 10 BLV copies.…”

Section: Introductionmentioning

confidence: 99%

Tracing Viral Transmission and Evolution of Bovine Leukemia Virus through Long Read Oxford Nanopore Sequencing of the Proviral Genome

et al. 2021

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Bovine leukemia virus (BLV) causes Enzootic Bovine Leukosis (EBL), a persistent life-long disease resulting in immune dysfunction and shortened lifespan in infected cattle, severely impacting the profitability of the US dairy industry. Our group has found that 94% of dairy farms in the United States are infected with BLV with an average in-herd prevalence of 46%. This is partly due to the lack of clinical presentation during the early stages of primary infection and the elusive nature of BLV transmission. This study sought to validate a near-complete genomic sequencing approach for reliability and accuracy before determining its efficacy in characterizing the sequence identity of BLV proviral genomes collected from a pilot study made up of 14 animals from one commercial dairy herd. These BLV-infected animals were comprised of seven adult dam/daughter pairs that tested positive by ELISA and qPCR. The results demonstrate sequence identity or divergence of the BLV genome from the same samples tested in two independent laboratories, suggesting both vertical and horizontal transmission in this dairy herd. This study supports the use of Oxford Nanopore sequencing for the identification of viral SNPs that can be used for retrospective genetic contact tracing of BLV transmission.

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Bovine leukemia virus detection and dynamics following experimental inoculation

Cited by 15 publications

References 26 publications

Bovine Leukaemia Virus: Current Epidemiological Circumstance and Future Prospective

Bovine Leukaemia Virus: Current Epidemiological Circumstance and Future Prospective

Diagnostic Measures of Disease Progression in Cattle Following Natural Infection with Bovine Leukemia Virus

Tracing Viral Transmission and Evolution of Bovine Leukemia Virus through Long Read Oxford Nanopore Sequencing of the Proviral Genome

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