HI hope this helps a friend had similar prob a few years ago. He gave baytrill and still tested pos 6 days later so an old well trusted local fancier gave him this advice and it seemed to do the trick. put 1 table spoon honey to 1 liter of water with 1 table spoon of cider vinegar to the same water for 6 days then birds will have started some of there health back after which get belgica de weerdes parastop from mercasystems and treat them for 14 days this did the trick