Stand by your man - swing by the feed store and get him a small tube of Safegaurd and of Equimax, which should last about 2 weeks. He'll know within a few doses if worms are his problem. This approach is cavalier, but when I was desperate they were lifesavers.
Research ICU protocols if you can get scripts, scabdraggr protocol if you can't and aren't afraid of vet meds.