Ridecamp: [RC] pigeon fever -contagious?

Trying to determine if I need to scratch plans to attend a ride
this sat.  Couple horses on our place have pigeon fever.  No sign
of it on Grey Moun, but I dont want to take him somewhere if he
could be contagious, and it sounds like they can have the bacteria
before they show any swellings.  Also I separated him, but they
have a common water tank.  Can it be spread in the drinking
water, or is spread caused only by flies, or direct contact
with an oozing abcess?   

Also what is recommendation for antibiotics?  I did a bit of
web searching and it sounds like some vets recommend against
antibiotics for external swelling/abcessing.  The first horse
is already getting antibiotics, but since Shade has so many
nerve endings (she feels -and resents- shots even when twitched)
I'm holding off on giving her penicillan; and our vet said the
oral antibiotics are not as effective.  Seems to be some thinking
that antibiotics could increase chances of internalized abcessing;
hopefully not if an abcess has already opened like it has on 
Star.  

Thanks in advance,

-- 
Teresa Van Hove, and Grey and Shade

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