it sounds like your koi could have the same infection too? i'm not sure the best way to treat bacterial infections, but i have found 'pp' does work if you treat them early try asking here http://forum.koimag.co.uk/ for help
yes spudsy i lost 5 large koi and some small, they got out under the decking through a small opening. my neighbour lost all but one, this has since died due to infection 22" chagoi.