|
Contents
|
|
Foot and mouth disease (FMD) is a highly contagious disease with the potential to
damage severely the livestock industry of any country. In an FMD outbreak morbidity
is often high, although significant mortality is usually confined to young stock.
Explosive epidemics can occur due to several factors:
• a diverse host range, which includes all domestic and wild
cloven-hoofed animals
• a low infectious dose requirement
• high titre virus excretion, especially as aerosols from
infected pigs
• relative environmental stability as a non-enveloped virus
• multiple transmission routes, including oral, inhalation
and transepithelial
• a short incubation period
• wide antigenic variation complicating disease control
even in vaccinating regions
The disease is endemic in many regions of the world, including much of Africa, Asia
and some countries in South America. In many countries the disease is tolerated as
there are insufficient resources and infrastructure to control it effectively. Control
of FMD in endemic regions relies heavily on mass prophylactic vaccination with inactivated
viral vaccines, which are frequently multivalent. Movement restrictions with the possible
use of supplementary vaccination, with or without slaughter of diseased animals, may also
be used to control an outbreak. In FMD-endemic regions the major cost of the disease is
associated with reduced livestock productivity, regular mass vaccination and reduced
access to international markets for livestock and livestock products. The achievement
and maintenance of FMD-free status therefore has major benefits for international trade.
Regions free of FMD include Europe, Australasia, Japan and North and Central America.
Here, control is based upon prevention of introduction of the virus through rigorous
importation regulation and quarantine.
Control of FMD was achieved in most of Europe through mass annual vaccination campaigns
conducted in the second half of this century. Countries may go through a phase of being
recognised by the Office International des Epizooties (OIE) as 'FMD free with vaccination'
but, once full freedom from FMD is achieved, prophylactic vaccination is no longer allowed
due to the difficulty of differentiating infection from vaccination. In most FMD-free
countries access to strategic antigen reserves is maintained for emergency use in
extensive outbreaks not controlled by slaughter and zoosanitary measures alone. Together
with surveillance and diagnostic facilities, maintenance of these FMD 'vaccine banks' is
one of the ongoing costs of FMD control in FMD-free regions.
|
