Controlling bovine leukemia virus in dairy herds by identifying and removing cows with the highest proviral load and lymphocyte counts
A pilot intervention trial revisiting the concept of selective culling and segregation for BLV positive cattle in an effort to reduce BLV transmission.
Published by Ruggiero, B. Norby, O.J. Benitez, H. Hutchinson, K.R.B. Sporer, C. Droscha, C.L. Swenson, P.C. Bartlett
Objective: To reduce bovine leukemia virus (BLV) transmission and prevalence in commercial dairy herds using proviral load (PVL) and lymphocyte count (LC) measurements as indicators of the most infectious animals for culling or segregation.
Hypothesis: They hypothesized that BLV within-herd transmission and prevalence could be reduced by identifying and removing (culling or segregation) ELISA-positive cows with the highest PVL and LC.
Location: Michigan and Wisconsin
Methods: Milk or blood samples from adult cows in our 3 Midwestern dairy farm field trials were tested semiannually with ELISA for BLV antibodies, and ELISA-positive cattle were then retested using a blood LC and a quantitative PCR test for PVL to identify the animals presumed to be most infectious. Herd managers were encouraged to consider PVL and LC status when making cull decisions, and to segregate cows with the highest PVL and LC from their BLV ELISA-negative herd mates where possible.
Outcomes: After 2 to 2.5 yr of this intervention, the incidence risk of new infections decreased in all 3 herds combined, from 13.8 to 2.2, and the overall herd prevalence decreased in all 3 herds combined from 62.0 to 20.7%, suggesting that this approach can efficiently reduce BLV transmission as well as prevalence. This is encouraging, because a very low prevalence of BLV infection would make it economically feasible to cull the remaining ELISA-positive cattle, as was achieved in national eradication programs in other countries decades ago.
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By Eric R
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Controlling bovine leukemia virus in dairy herds by identifying and removing cows with the highest proviral load and lymphocyte counts
A pilot intervention trial revisiting the concept of selective culling and segregation for BLV positive cattle in an effort to reduce BLV transmission.
Published by Ruggiero, B. Norby, O.J. Benitez, H. Hutchinson, K.R.B. Sporer, C. Droscha, C.L. Swenson, P.C. Bartlett
Objective: To reduce bovine leukemia virus (BLV) transmission and prevalence in commercial dairy herds using proviral load (PVL) and lymphocyte count (LC) measurements as indicators of the most infectious animals for culling or segregation.
Hypothesis: They hypothesized that BLV within-herd transmission and prevalence could be reduced by identifying and removing (culling or segregation) ELISA-positive cows with the highest PVL and LC.
Location: Michigan and Wisconsin
Methods: Milk or blood samples from adult cows in our 3 Midwestern dairy farm field trials were tested semiannually with ELISA for BLV antibodies, and ELISA-positive cattle were then retested using a blood LC and a quantitative PCR test for PVL to identify the animals presumed to be most infectious. Herd managers were encouraged to consider PVL and LC status when making cull decisions, and to segregate cows with the highest PVL and LC from their BLV ELISA-negative herd mates where possible.
Outcomes: After 2 to 2.5 yr of this intervention, the incidence risk of new infections decreased in all 3 herds combined, from 13.8 to 2.2, and the overall herd prevalence decreased in all 3 herds combined from 62.0 to 20.7%, suggesting that this approach can efficiently reduce BLV transmission as well as prevalence. This is encouraging, because a very low prevalence of BLV infection would make it economically feasible to cull the remaining ELISA-positive cattle, as was achieved in national eradication programs in other countries decades ago.