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cow and calf

Bovine Leukosis (BLV)

  • Blood-borne viral infection with no effective vaccine
  • Negatively impacts production, longevity and cull value
  • Utilize ELISA analyses and strategic pooling to reduce testing costs
  • Producers can screen cows by ELISA then submit samples from BLV-positive cows for SS1 qPCR testing.
    • The SSI qPCR test can identify susceptible cows that have become “Super Shedders,” causing the most risk to uninfected herdmates and youngstock.

Sample Type(s)

  • Milk, individual or bulk tank (fresh, frozen or preserved)
  • Serum (ELISA)
  • Whole Blood (SS1 qPCR or ELISA)


  • Test milk at dry-off or fresh
  • Herd Profile ELISA Test estimates herd prevalence by testing 10 cows each from lactations 1, 2, 3, and 4+ at DHI test
  • Test blood by ELISA on animals over 4 months
  • Test blood by SSI qPCR at any age


  • Available within 5 business days of sample receipt
    • Reported as Positive, Negative or Suspect
  • SS1 qPCR results available within 10 business days of sample receipt
    • Reported as High, Moderate, Low, or Undetected with a numeric value indicating the number of BLV copies per white blood cell.
Test Type Positive Negative Suspect
Milk ELISA >0.3 <0.1 0.1 – 0.3
Bulk Milk ELISA >0.1 <0.1
Blood ELISA >1.0 <0.5 0.5 – 1.0


Milk Samples:

  • Animals that are within 7 days of freshening have a high probability of giving false positive results when tested because of the presence of colostral antibodies.
  • A suspect result for the Milk ELISA may indicate carryover from a previous Leukosis positive cow in the milking string and should be retested with a hand-stripped sample.
  • A suspect Blood ELISA test should be retested.


  • Individual ELISA (milk, blood) $6.50/sample
    • Multiple test discount! $11for two ELISAs on same sample; $15.00 for 3 ELISAs
  • Individual SS1 qPCR $12/test
  • Group ELISA (pooled or bulk milk) $20/test
  • Testing billed upon sample receipt
  • $10 sample submission fee per order

Submit Samples

Additional Information

BLV affects 84% of all dairy herds and 33% of all beef herds in the U.S.

Dr. Don Niles and leading Michigan State University (MSU) researcher, Dr. Tasia Kendrick, discuss recent research efforts that will help you manage the effects of BLV on dairy- and beef-cattle health and productivity.

CentralStar Laboratories

CentralStar’s Laboratories provide sample analyses on milk, blood, fecal, and tissue samples for a variety of production, disease and health-related traits.

More than 5.3 million samples are processed annually using state-of-the-art equipment and techniques including infrared spectroscopy, flow cytometry, ELISA, PCR, and more.

Testing Supplies

For convenience, shippers and sampling supplies can be purchased online.

Diagnostic tests are intended to identify diseases in the cow for their health, and do not determine the “safety” of milk. Testing prices listed effective 10/1/2020. 

How To Collect a Blood Sample for Serum Tests

Supplies Needed:

  • Vacutainer® Vial
  • Double-sided needle
  • Needle holder

Be sure to check which type of vial is required for your desired test type.

  • Red-top vials: Pregnancy, Johne’s, Leukosis, BVD and Neospora.
  • Purple-top vials: A1/A2 and BLV SSI PCR.
test step 1

Step 1:

Screw needle into needle holder
Insert the Vacutainer vial into the holder
DO NOT puncture the vial stopper

test step 2

Step 2:

Lift the tail straight up and clean area
Find the midline groove 4 to 6 inches from the base of the tail
Insert the needle about ¼ inch into the groove, perpendicular to the underside of the tail

test step 3-4

Step 3:

Engage the vacuum by pressing the vial up puncturing the stopper
If blood does not flow, carefully redirect the needle
DO NOT remove the needle from the tail

Step 4:

Once blood begins to flow maintain needle position
Collect a minimum of 4cc of blood

test step 5

Step 5:

Disengage the vial from the holder BEFORE removing needle from the tail

test step 6

Step 6:

Clearly label vials with animal identification
Fill out a sample submission form

Step 7:

Keep vials at room temperature to allow clotting (1 to 2 hours)
Once clotted, keep samples refrigerated until submitted to the lab

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