Sorry for your losses..
if you have not already, I'd suggest you look up goat polio and listeria symptoms, causes and treatment. Wet environments are key for that bacteria to build up, get ingested and cause havoc on the rumen and lead to neurological problems that most times untreated leads to death. Onset of symptoms happens rapidly. If you already have explored this, please disregard, just trying to help...one goat rancher to another.