Washington, DC (3/23/01)- In spite of enormous preventive efforts,
including canceling all St. Patrick's Day activities, Ireland has now joined
the list of European countries reporting cases of foot-and-mouth disease (FMD).
In addition to England, where the outbreak started, other affected countries
now include Scotland, Wales, France, and the Netherlands, with possible cases
in Germany, Spain and Italy. The epidemic is already beginning to cause significant
social and economic hardship. Will the US be next?
FMD- What is IT?
Foot-and-Mouth disease is a highly contagious viral disease that affects
cattle, sheep, pigs and a variety of other domestic and wild cloven-hoofed
animals. Humans infection is extremely rare, but can occur in association
with direct contact with infected tissue. The disease is caused any of several
serotypes of the Picornaviridae/Aphthovirus family. The seven most
common serotypes, called A, O, C, Asia1, SAT-1, SAT-2, and SAT-3, each contain
many subtypes. The current strain has been named the Pan Asian variety.
Infected animals develop lesions and sores on hooves, mouth and other areas.
Younger animals are most likely to die from the disease, while mature animals
may survive, but with problems including: weight loss, foot damage, poor milk
production and infertility. The disease's incubation period is two to eight
days.. It takes two to three weeks to clear foot and mouth from an area once
the disease is quarantined.
FMD is not related to 'Mad Cow Disease', or bovine spongiform encephalopathy
(BSE). Outbreaks of BSE in England, Ireland and continental Europe have been
traced to animal feed containing infected animal parts. Outbreaks of a related
disease in humans, CJD, led researchers to believe consumption of infected
beef could put humans at risk. The BSE outbreak had already forced British
and other farmers to slaughter herds of cattle.
How is FMD Spread?
FMD is one of the most contagious of all animal diseases. Infection can occur
through inhalation, ingestion and/or reproduction. The disease can spread
quickly through a herd of animals via direct contact and by inhalation of
virus aerosols. The wind can carry the virus great distances. The disease
can spread easily when an infected animal is moved to an uninfected herd.
The virus can also 'hitchhike' a ride on farm vehicles, equipment, people
and products.
Once an animal is infected, the virus can survive for a long time, even after
the animal is dead. The FMD virus can survive for quite a while in meat if
the pH does not fall below 6.2. It can also survive in frozen, salted and
cured meats, and in non-pasteurised dairy products.
The highest risk of entry of FMD is through imports of susceptible live animals,
contaminated meat or dairy products from infected countries. Virus can survive
for long periods in a range of fresh, partially cooked, cured and smoked meats,
and in inadequately pasteurized dairy products. These could be brought in
with passengers on aircraft and ships, through the mail or on fishing vessels
or yachts.
Where is It?
The current European outbreak began in the United Kingdom, where 500 animals
have been confirmed to have the disease. Infected animals have also been identified
in the Netherlands, France and Ireland, with suspected cases in several other
European countries. In the past year, FMD outbreaks have been reported in
Russia, China, South Korea, Taiwan, Japan, Mongolia, and at least seven African
and five South American countries. The disease is endemic in parts of Africa,
Asia, the Middle East and South America.
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Where's
the Beef?
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What is Being Done?
The effort to prevent the spread of FMD is now global. In areas where infected
animals have been discovered, farmers have no choice but to 'cull' entire
herds of animals, whether or not the animals are known to be infected. This
is because infected animals start producing new virus particles before showing
any symptoms.Throughout the United Kingdom, skies are dark with smoke from
mountains of burning carcasses. The problem is so great that the British Army
has been called in to help with the cull.
Considerable efforts are also underway to discourage travel in affected areas.
Horse races, livestock fairs, local festivals and parades have all been banned
in England and Ireland, for example. Ironically, farmers in affected areas
cannot even go the polls to express their reaction, since they are forbidden
to travel locally. Tourism is being severely affected by the FMD epidemic,
since many of the more popular beauty spots are now off limits. Travelers
leaving affected countries are subject to search at other ports of entry and
are required to undergo disinfection procedures. Norwegian authorities even
went so far as to cancel its annual reindeer races.
British authorities say the problem is likely to get far worse before it
gets better. The worst case scenario could involve the destruction of more
than half of the 60 million livestock animals in Great Britain alone. This
could cost Britain $1billion. The effects of lost tourism could go far higher,
up to $13 billion, British authorities say.
What
About a Vaccine?
A vaccine against FMD has been available for many years. As with the flu
vaccine, the FMD vaccine is formulated for specific subtypes associated with
particular outbreaks. The vaccine has been proven effective in protecting
livestock. So why wasn't it being used? In short, it appears that economics
and politics are to blame. With FMD apparently eliminated throughout Europe
and the US, governments felt it was difficult to justify the expense. In fact,
until just a couple of days ago, it was the official policy of the European
Union to prohibit the use of the vaccine. This was because the vaccine, although
effective, produced the same antibodies that would be seen in infected animals,
making it difficult to screen for the disease. Many countries, including the
US and Japan would not import vaccinated cattle or meat from vaccinated animals
for this reason. The vaccine is made from killed, not attenuated, virus. This
can produce another problem, where in some cases inadequately killed virus
could cause infection rather than protection.
Faced with a true epidemic, the European Union recently reversed itself and
approved the limited use of the vaccine. The Netherlands has begun a vaccination
campaign, and Britain and other countries may soon follow. The original concern
about antibodies confusing the screening process is now considered less of
an issue. in fact, assays that can make the distinction have been available
since 1997.
One company, United Biomedical
developed a peptide-based test that can simplify the diagnosis of FMD. The
same company has developed a synthetic peptide-based FMD vaccine. The efficacy
of the vaccine is now being studied. Early indications are that the vaccine
can neutralize multiple serotypes of the virus.
Is the USA Next?
The United States has been free of foot and mouth disease since 1929. Yet
many biologists now think it is not of matter of if, but when, it will arrive
in the US. Despite massive precautions at US ports of entry, the virus can
hitchhike in livestock or on clothing. A recent article in the journal Science
concluded that a limited outbreak in a single county in California could cost
$1.5 billion. Should an outbreak occur in the US, there would be no choice
but to follow the 'quarantine and cull' practices now in place in England.
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