Did you vet do 2 skin scrapings after the ivermec injections to be sure it was gone? Personally I'd seek a second opinion for treatment.


Best site for info...

VeterinaryPartner.com demodectic mange


Site has some info......

vetinfo.com

There are three treatments for demodectic mange that work for most dogs.
The first is the use of amitraz pour on (Mitaban Rx)Product No Longer Available! every other week
for 6 to 8 applications or until 2 consecutive skin scrapings are negative,
which probably cures demodectic mange in about 80% of dogs when
application directions are followed, although this is just a guess based on
averaging results from available studies. This is the only approved treatment for
demodecosis. The second treatment is ivermectin given by injection or
orally at the rate of 250ug/kg or higher (up to 600ug/kg in resistant
cases) daily until two skin scrapings are negative, which probably also
works about 80% of the time. This treatment has to be used very
carefully in collies and shelties, who are more likely to suffer toxic reactions
to ivermectin. The third treatment that is sometimes used is oral
milbemycin (Interceptor Rx) given daily for six to eight weeks and my best guess is
that it is about as effective as the other therapies. It is probably
wise to be cautious about using this therapy in collies and shelties, too --
although we have done this on a couple of occasions without problems, so
far.

Even though we use six to eight weeks as sort of a minimum therapy time,
it is important to remember that it can take up to a year of therapy in
some dogs to cure demodecosis. It might be possible to cure more dogs if
intense treatment was used longer than a year but we haven't tried that.

Some dogs who do not respond to one therapy will respond to one of the
others, so it is probably possible to cure demodectic mange in about 90%
of dogs. In the remaining dogs it is usually possible to control the
disease even if it can't be eliminated, by use of intermittent therapy. We have
done once a month amitraz applications when this was necessary, in most
cases. We have a couple of patients who we use ivermectin intermittently
with (probably average two or three month long treatments a year).