White line disease is a bacteria that affects the white line. The white line is not white it is just a name. It is located between the hoof wall and the sole of the foot. What it really comes down to is the white line is dead laminae. Which is a velco like substance that attacks the hoof wall to the coffin bone. The stretching of the white line is not white line decease. White line decease is were the white line is being eatened away by bacteria. In other words there will be a space between the sole and the hoof wall were the white line use to be. The bacteria can also weaken the hoof wall causing flaring. Flaring is were the hoof wall grows outward instead of downward.
Causes of white line decease is an environmental issue. Some soils can contain high amounts of bacteria. To much mud and muck will cause white line as well as rubber mats. Yes, rubber mats don't allow the bacteria to drain. The bacteria is left on the surface were it is picked up by the horse's hooves. Treatment: I fine the best thing is an old dish washing fluid bottle of dawn, sunlight, etc, emptied out and filled with 50% bleach and 50% water. If you have bleeding don't use!!! If bleeding use peroxide. Bleach is for external application only. Bleach will burn in open cuts and wounds. There are lots of commerical products too.