Bovine Leukocyte Adhesion Deficiency (BLAD)

1. What is BLAD?
2. What are effects of BLAD?
3. What are the chances of a positive cow producing a positive calf?
4. How is BLAD diagnosed?
5. Where and how can I have my cow tested?

What is BLAD?

Bovine leukocyte adhesion deficiency (BLAD) is a genetic disease that affects Holstein cows. A human equivalent also exists called human leukocyte adhesion deficiency. It is caused by a hereditary genetic mutation that disrupts the function of a receptor protein on leukocytes. Leukocytes are blood cells that are involved in immunity and the fighting of infectious diseases. When a cow gets an infection, leukocytes are attracted to the tissues that are affected and will fight the invading organism. The leukocytes are attracted to the site of infection by molecules that appear on the walls of the blood vessels in the infected region. In order to stop and enter the tissue, the leukocytes use one of their receptors to attach to these molecules and anchor themselves so that they can go through the wall of the blood vessel and into the tissue. The mutation associated with BLAD changes the receptor on the leukocyte so it will no longer anchor the leukocyte and will not be able to get into the tissue to fight the infection. As a result, affected cows cannot fight off common bacterial diseases which may persist or recur.

What are effects of BLAD?

Cows with BLAD can experience persistent and recurrent infections including gingivitis, periodontitis, pneumonia, loss of teeth and stunted growth associated with marked neutrophilia. The body weight of affected cows may be 50-60% of the expected weight. Prognosis of this disease, although fatal, may be closely related to the degree and sites of inflammation and affected organs.

What are the chances of a positive cow producing a positive calf?

If a cow carrying one copy of the mutant gene - a heterozygote - is mated with an unaffected bull, there is a 50% chance that the calf will be a heterozygous carrier for the mutation but will not exhibit the symptoms of BLAD. If the cow carries two copies of the mutant gene - a homozygote - all offspring will be either heterozygous carriers or homozygotes with the symptoms of BLAD depending on the status of the bull. If two heterozygous carriers are mated, there is a 50% chance that the foal will be affected with BLAD or will be a carrier. Two unaffected cows cannot produce a positive calf.

How is BLAD diagnosed?

The best way to determine whether a cow is a carrier or homozygous for the BLAD mutation is a DNA test. The identification of this gene mutation is the basis for the DNA test used to diagnose BLAD. This test is more accurate, less expensive and faster when compared to traditional testing procedures.

Where and how can I have my cow tested?

VITA-TECH Canada Inc. proudly offers the BLAD DNA test at a highly competitive rate. Simply submit a completed requisition form and a whole blood sample (1-5 ml) in an lavender top EDTA Vacutainer tube labeled with the cow's name, the name of the owner or the responsible agent. Requisition forms are available upon request at no extra cost. The sample may be shipped directly to us using any two-day or next-day courier or mail service in a padded and leak-proof package. U.S. clients are asked to attach an importation permit to the package which we also provide at no extra charge.

We are proud to offer this quality service and look forward to your patronage. Our friendly, helpful staff is available to answer any questions you may have from early morning to late evening, six days a week. For inquires regarding BLAD and other DNA tests or any of our other services, please do not hesitate to contact us.