IT鈥橲 just what vets in Britain have been praying for鈥攁 portable test
that can tell them within an hour if an animal has foot and mouth disease.
Developed in the US, the test is being evaluated in Britain this week. If it
works, it could greatly speed up the vital task of identifying infected animals.
It would be especially valuable for sheep, in which the symptoms are very hard
to spot.
At present, samples from animals have to be sent to off to a lab for testing.
This can cause delays of a day or more. So vets battling the outbreak in Britain
are now condemning suspect flocks to slaughter merely on suspicion. An
on-the-spot test would be invaluable for speeding up diagnosis and preventing
unnecessary slaughter.
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Bill Nelson of Tetracore of Gaithersburg, Maryland, the company that
developed the test, arrived in Britain last weekend with an official from the US
Department of Agriculture to put the test through its paces. 鈥淭he question is
whether it鈥檚 of any value at this point in the epidemic,鈥� Nelson says.
The test is based on PCR, a way of making large quantities of a predetermined
鈥渢arget鈥� fragment of DNA or RNA. In this case, the target is the RNA coding for
an enzyme called 3D-polymerase that enables the foot and mouth virus to
replicate. All seven major strains of the foot and mouth virus have this enzyme
in common, so the test should spot them all. 鈥淲e look at saliva, tissue or
blood,鈥� says Nelson. 鈥淎t Plum Island, we鈥檝e proved it works in pigs, sheep and
cattle, at least for saliva,鈥� he says.
Tetracore has managed to squeeze all the equipment needed for PCR into a box
about a foot square. Vets would simply put a sample into a small tube pre-loaded
with the necessary reagents. The box can analyse 16 samples at a time. 鈥淲e use a
laptop computer to run it,鈥� says Nelson. 鈥淚t takes about an hour.鈥�
鈥淚f you had 100 sheep, you could test individual sheep or combined samples
from, say, 10 at a time,鈥� says Fred Brown, a foot and mouth researcher at Plum
Island. This means you could screen entire herds very rapidly, he says.
Nelson stresses that the test has yet to be validated. 鈥淲e don鈥檛
know till it鈥檚 been test-driven whether it works,鈥� says Nelson. The equipment is
not cheap either, at $28,000. But it could pay its way if it spots
infected animals quickly.