Fly parasite

["Randall Aldridge" <limberlost@worldnet.att.net>]

Hi,

My mare has a problem w/onchecirca (sp?), that fly parasite that makes
horse itchy.  I was wondering if anyone has any experience with or remedies
for it.  As long as I've had her (3yrs) every summer we go thru this.  Last
year was real bad & used Azium along w/occasion steriod injections & prayed
for winter to come.  This year she's been much better until the last few
weeks.  I practice good fly control but even so some of those pesky
critters manage to survive (started Equitrol in Feb., keep it clean, etc). 
We worm w/Ivermectin every 3-4 weeks in the summer.  She had been doing
much better than last year but now it's like she's exploded into one giant
itching, rubbing maniac.  She looks horrible w/rub & scratch marks all
over.  She due to be wormed this weekend but the last dose only seemed to
last about 2 weeks before she started itching.  This makes it hard to ride,
she starts getting itchy after a few miles & all she can think about is
trying to scratch under her saddle.  Last year she would go down on trail
to try to roll.  I'm thinking about putting her on Nemicide (dog heartworm)
(per vet last year) after this deworming.
So, any ideas?  How about any holistic remedies & where to get them? I'd
like to stear clear of steriods if possible.

Thanks in advance,

Christina