Moving to zero prevalence of bovine leukosis

Taking on a seemingly intransient disease can be a winning battle with new tools provided through grants from the Michigan Alliance for Animal Agriculture.

BLV can be diagnosed through ELISA testing on either milk or blood serum samples.

Bovine leukemia virus (BLV) is a widespread infector of cattle, invading the lymphocytes, a type of white blood cell, causing an impaired immune response. At this time, the disease is incurable and untreatable. While only a small percentage of cases may become clinical, the subclinical impacts are decreased milk production, increased impacts of other diseases, and decreased life in the herd.

In the U.S. and Canada, it has been shown that approximately 85-90% herds are infected, however, the prevalence within herd can vary from a few animals to the majority of animals, and averages about 45% in U.S. dairy herds. Annually, the cost to a dairy herd with the average prevalence of BLV is approximately $270 per cow in the herd. Controlling the spread of the disease is the only management option for herd owners, and that can be done through reduced risk of virus transmission in even microscopic blood amounts and by culling positive animals, especially those that are shedding the virus at a high rate.

Diagnosis is typically done by an ELISA test on a blood or milk sample. ELISA, enzyme-linked immunoassay, is a common diagnostic test that detects specific antibodies produced by the animal in response to exposure of the disease agent.

Michigan State University Extension was recently awarded an Extension grant from the Michigan Alliance for Animal Agriculture (M-AAA) to help herd owners with low prevalence of BLV identify and remove cows that are ELISA-positive for BLV, and to develop a program that recognizes BLV-free status in Michigan.

As an MSU Extension educator and primary investigator on the project, “Moving to Zero: Developing a pathway to eradicate BLV from Michigan dairy herds,” this is an important step to provide a goal for all farmers with the potential for economic benefit in attaining it.

For owners of cattle herds that achieve zero prevalence and who desire recognition of that status, the Moving to Zero project will propose a system to designate herds as BLV-free to the state. Several states have recognized BLV-free status. It is hoped that a state system in Michigan could be a model for a national recognition program. Getting herds to zero is only part of the battle; maintaining that status through vigilance and testing is also needed.

Eradicating BLV is not easily nor quickly done. While we know much about transmission of the disease, it is apparent that even when farmers use recommended practices, including single use of needles and exams sleeves, that disease prevalence can remain high. For herds with prevalence rates above 20%, culling all positive animals without serious negative economic effect is a long-term process. Yet, some herd owners have committed to reduce and even eradicate BLV from their herds.

Howard Straub, III is the manager of the MSU dairy herd at Kellogg Biological Station, a herd of 180 cows. At the high point of BLV in the herd in 2015, 62% of cows were ELISA-positive for BLV. Through patience, persistence, and practice changes along with selective culling over a six-year period, Straub has been able to get the herd prevalence down below 10% and is planning, as a cooperator in the Moving to Zero grant project, to eradicate the disease this year.

In another project funded by an M-AAA research grant titled, “The economic impact of Bovine Leukosis Virus in Michigan dairies,” primary investigator and MSU assistant professor Melissa McKendree says, “Our project measures the economic impact of BLV and economic-effectiveness of a test and cull management program by pairing financial data from TelFarm and herd management data from PC Dart. We’ll create a dairy producer partial budget decision tool where producers can enter their farm-level data into a spreadsheet to estimate differences in economic profitability over a 10-year period under multiple test and cull BLV management strategies.”

Any incremental change in BLV prevalence has benefits, but as long as BLV is in a herd, it will continue to spread. MSU, in partnership with CentralStar Cooperative are world leaders in the efforts to help cattle farmers gain control over BLV. Casey Droscha, associate director of research and development at Antel Biosystems, a unit of CentralStar Cooperative, sees BLV in cattle herds as “an important emerging issue in a changing consumer landscape.” Herd owners need to consider the future marketplace and the demands that consumers will have and work toward eradication of BLV now.

Work at MSU on BLV has been the focus of a team of research and Extension individuals for more than 10 years. Paul Bartlett, retired MSU professor and BLV team leader said, “The experiment that first got our attention was one that showed reduced immune response in BLV-infected cattle to the J-5 vaccine.” Because vaccination is an important health protection practice for cattle herds, this represented a significant limitation for cattle health programs.

The BLV team at MSU and CentralStar believe that getting herds to zero prevalence is important from the perspectives of farm economic gains and animal well-being, and thus consumer acceptance. You can learn more about BLV at

The M-AAA is a partnership between Michigan animal agriculture and allied industries, the MSU College of Agriculture and Natural Resources, MSU College of Veterinary Medicine, MSU AgBioResearch, MSU Extension and the Michigan Department of Agriculture and Rural Development focused on advancement of the Michigan animal agriculture economy. Grants in 2021 for dairy-related projects totaled more than $1.6M, an investment in the state’s number one agricultural industry. For more about these research projects, contact the author at

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