Bovine Leukocyte Adhesion Deficiency (BLAD)
BLAD is a genetic defect affecting white blood cell function which causes extreme susceptibility to infection. Genomnz can test for the mutation in the CD18 gene that causes leukocyte adhesion deficiency in Holstein cattle.
Bovine leukocyte adhesion deficiency (BLAD) is a recessive disease and results in an affected animal’s white blood cells failing to attach to the cells lining the blood vessels, an essential step in their migration to the point of infection to destroy invading pathogens. Affected calves suffer from recurrent bacterial infections of the respiratory and gastrointestinal tracts and eventually succumb to infection.
Research has identified the specific DNA code that causes BLAD in Holstein cattle. BLAD carriers have a mutation or SNP (single nucleotide polymorphism) in the DNA sequence changing an adenine (A) nucleotide to a guanine (G) nucleotide at position 383 of the CD18 gene.
The test identifies three classes of animal:
Where the CD18 genotype is AA the animal does not have the disease.
Where the genotype is AG the animal has one copy of the mutated gene and one copy of the normal gene so although it may not show signs of the disease it will pass the mutation on to about half its offspring.
Where the genotype is GG the animal will be affected by BLAD, show clinical symptoms, and will die at an early age.