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Packaging
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After collection, the sample should be poured from the probang
cup into a suitable wide-necked bottle and examined visually for quality.
Two ml, which should contain some visible cellular material, should then
be added to the previously prepared bottle containing an equal volume
of buffer, and thoroughly mixed by gentle shaking. The final pH of a normal
sample should be pH 7.6. If it is grossly different a second sample should
be collected after washing out the animal's mouth with saline.
Samples which are heavily contaminated with ruminal contents should be
discarded. The animal's mouth should be flushed with water or physiological
saline solution before repeat sampling. If a second sample is still contaminated
then the procedure should be abandoned and repeated the following day.
Samples from sheep tend to be small, mucoid and difficult to detach from
the probang cup. The easiest procedure is to insert the probang cup directly
into a disposable bottle or similar container into which has been dispensed
3 ml of buffer solution. The probang cup is then shaken in the buffer
solution to free the sample from the cup, and the sample together with
the buffer, is poured into a previously labelled bottle for transport.
Between collections from each animal, probang cups should be disinfected
in a bucket containing 4% sodium carbonate (Na2CO3)
or 0.2% citric acid. After disinfection, the probang cup should be thoroughly
rinsed in running tap water, or at least three separate buckets of clean
water in series.
The extent of virus shedding into O/P fluid decreases with time after
infection. In many carrier animals virus is shed only intermittently after
the initial clinical phase of the disease. A single negative result is
not therefore sufficient evidence that an animal is not a carrier of FMD
virus. At least two O/P samplings, separated by several weeks, together
with a negative serological status, are the minimum requirements to certify
freedom from FMD virus.
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