The caudal fold test, which has been in use for over 100 years, may be in for a long-overdue retirement, according to CFIA senior vet Dr. Maria Koller-Jones.
A new blood-screening test, called fluorescent polarization assay, or FPA-TB, was validated and approved for use in 2007 by the CFIA. Since then, it has been used in 12 provincially registered abattoirs in western Manitoba, and is deemed to be as, or more effective, than a routine post-mortem inspection.
Unlike caudal fold testing (CFT), which involves the injection of a TB protein extract in the skin of an animal’s tail and a re-examination of the spot 72 hours later, the FPA-TB test requires that only a single blood sample be drawn from each animal.
It’s not quite ready for prime time, however, said Koller-Jones.
In its current form, the FPA-TB test will catch infected animals 70 per cent of the time, compared to caudal fold testing, which has a sensitivity rate of over 80 per cent.
However, at least three “heavy hitter” diagnostic research companies in the U. S. are working on improving similar blood tests, she said, and a CFIA researcher is looking at ways to boost its sensitivity rate.
If it can be boosted to match CFT’s sensitivity, the days of tuberculin injections – and farmers’ concerns over their possible effect on animal health with repeated use – will be over.
“There is a lot of research being done on the FPA-TB to try to improve that number, but currently it misses too many infected animals for us to use it instead of the skin test,” she said.
“We would love nothing better than to use a blood test as a screening test when science and research gives us one.”