Originally Posted by windspeed
Parasites may not be the problem. Horses that have problems in the sacrum/sacroiliac joint can sometimes 'self treat' their lower back pain by rubbing their butts against the wall etc. This will look like a parasite related tail rub.
Have an equine bodyworker check your horse out for any soreness or restriction in that area. Or learn some bodywork techniques to help your horse.
Good to know, thanks for the info
Oh, btw, hello fellow German