60% ratio???
It's serology, to show whether the bird HAS the antibody or does NOT (clean).
It shows whether the bird has ever even been exposed. According to Jack any 
pos. reaction should be checked out further. He suggests quarantining, then 
retesting the serology after 2 or 3 mos. If pos still then dna swab under 
stress. Basicaly then consider as carrier. Altho' the current also seems to 
be swabbing the nestbox on the premise that if the bird is shedding, that's 
where they'd shed....
TTYL,
Barbara
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