Foot and mouth strategy strengthened
Interferon could cover vaccines'
weak spot.
10 January 2003
HELEN PEARSON
 |
| Vaccination was shunned by
vets in 2001 as too slow to take effect. |
| © GettyImages |
|
|
An antiviral drug could avert future foot-and-mouth disease (FMD)
epidemics, scientists say1.
Combined with vaccination, the drug gives slow-acting vaccines
time to kick in.
More than 6 million animals were slaughtered in 2001 as
Britain struggled for 7 months to stop FMD tearing through
farmyards. Vets shunned animal vaccination because the virus
jumps from herd to herd before vaccines can take effect.
The antiviral drug interferon protects pigs from infection
for at least 24 hours, says Marvin Grubman of Plum Island Animal
Disease Center in Greenport, New York. Crucially, it starts
working within a day. "No vaccine can protect animals so
quickly," he says.
"It's potentially hugely significant," agrees FMD
epidemiologist Mark Woolhouse of the University of Edinburgh,
UK. At the time of the British outbreak, experts favoured
culling over vaccination. Taking 7 days to provide immunity, a
vaccine strategy might have worsened the epidemic, they feared.
Recent inquiries such as those by Britain's Royal Society
have recommended well-planned emergency vaccination - alongside
culling - should FMD return. "This finding tips the balance
towards vaccination," says Woolhouse.
Interferon - normally a chemical cry for help from
virus-infected cells to the body's immune system - is used to
treat patients with hepatitis B and C. But unlike human
interferon, no system exists for synthesizing large quantities
of the animal protein.
To deliver the interferon, Grubman and his colleagues
engineered harmless viruses to carry a pig interferon gene.
High doses of the virus delivered enough interferon to
protect pigs from clinical FMD. It seems to stop the virus
multiplying. And in unpublished work, Grubman's team found that
a shot of interferon alongside conventional vaccination
completely protected pigs from the disease for up to 5 days.
David Paton, who heads the Institute for Animal Health in
Pirbright, UK, points out that the studies must be repeated in
cattle - the main target for vaccination programmes.
Even so, "the work is very exciting and offers hope for the
future," says Paton. The Plum Island researchers are already
talking with commercial vaccine manufacturers. |
