If there's any need to retreat for Ringworm, try putting an appropriate dose of pure MSM in each meal daily. My cats got ringworm, & I read that conventional vets quarantine + regularly/repeatedly bathe them in sulfur baths + constantly sanitize their living areas.... I started putting appropriate sized doses of MSM in their meals, & within a few days notice their sores healing up.
They healed noticeably more daily until they were gone. The problem is worst through humid weather, but it's pretty easy to continue supplying their food with pure MSM until things dry out sufficiently. Maybe something like this will work for you, too. I hope so!