Optimization of the PCR test for the mutation causing bovine leukocyte adhesion deficiency

The recent emergence of the bovine leukocyte adhesion deficiency (BLAD) demonstrated the risks of narrowing the genetic basis of a population. About 6% of the Holstein-Friesian cattle now descends from one bull who was a heterozygous BLAD carrier. Crossing his descendants resulted in the birth of homozygous BLAD calves with a life expectancy of < 1 year. The BLAD syndrome is caused by a point mutation in the gene coding for CD18, a subunit of the beta 2 integrins on the surface of leukocytes. By using a PCR-RFLP test, large numbers of cattle are now being screened in several countries to eradicate the mutant allele. We describe an optimization of the PCR primer set that has led to an improvement of the test.