Dear Diana,
Have you asked your vet about something called Tylan powder?  Last summer
my vet was seeing lots of diarrhea, some of which responded to the usual
treatment and some of which lingered for months.  Tylan powder, whatever it
is, proved to be the medication that, within a day or so, stopped diarrhea
which had become chronic in his patients.  It clearly worked for Archie.
 
(Rustle didn't need it.)
Tell Chene to get well fast!
Jennifer
[Posted in FML issue 2423]