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Background:
FMD
is an extremely contagious viral disease of cloven-hoofed animals
which results in considerable economic losses. Especially in areas
of high animal density the epidemiology of the disease could take
a catastrophic course, leading to a situation where the usefulness
of established diagnostic tests would be limited. As an antibody
to structural proteins is produced following either infection
or vaccination, its detection does not distinguish between animals
which have merely been vaccinated and those which have been infected.
Emergency 'ring' vaccination may be needed as an adjunct to stamping
out to control the spread of infection.
Cattle,
including vaccinated cattle, can carry FMDV in their oropharynx
for up to 2 years. Therefore, if ring vaccination is performed,
it will be necessary to identify animals in which viral replication
has taken place in order to prevent the establishment of virus
carriers. As long as there are no diagnostic means available for
swift and broad-scale screening of vaccinated populations, the
economic value of vaccinated animal populations could collapse
due to the trade restrictions imposed in order to prevent further
spread of the disease.
Objectives:
The
objectives of the Concerted Action (CA) are to accelerate and
coordinate the development and validation of new methods for the
diagnosis of Foot-and-Mouth disease (FMD), especially those which
offer a chance to identify both infected contact holdings before
they become the source for a further spread of the disease, as
well as methods that could limit the economic consequences of
FMD for affected areas after emergency vaccination. The research
efforts of seven European FMD laboratories will be coordinated
during the next 3 years and 4 workshops will be organised.
Description:
The
European Commission sponsored a CA (1994-1997) to coordinate the
research into the potential use of assays measuring antibody to
the non-structural (NS) proteins of FMD virus, to differentiate
infected from vaccinated animals. In animals seropositive for
the antibody to structural proteins, the detection of the antibody
to the polyprotein 3ABC was found to be the most reliable single
indicator of infection. On a herd or group basis, measurement
of antibody to the NS proteins can be used to detect previous
infection in a vaccinated population.
Preliminary
results justify further research. However, absolute differentiation
of infection from vaccination is not possible by serological means
alone. For this reason, serology has to be complemented by other
assays. Currently, the established test to ensure freedom from
infective FMD virus in individual animals of a vaccinated population
is the probang test. This test, or a variant using nasal swabs,
is used to diagnose FMD where epithelial tissue is not available,
e.g. where infection is suspected in the absence of clinical signs.
This also applies to prodromal stages of disease, when considerable
amounts of virus can already be excreted, as well as to subclinical
cases, especially in small ruminants. Since the probang test is
laborious and time-consuming, broad scale screening of ruminants,
whether in contact holdings after a primary outbreak or in a vaccinated
area, is not feasible or would take too much time to be useful.
Principally, nucleic acid recognition methods are an alternative
to virus isolation. The polymerase chain reaction (PCR) can be
used to amplify genome fragments of FMD virus in diagnostic material.
However,
in order to at least match the sensitivity of virus isolation,
a nested PCR has to be performed. This method is laborious and
prone to give false positive results, so PCRs cannot currently
be employed for broad-scale screening campaigns or pre-movement
testing of large numbers of animals. Advanced PCR protocols ('PCR-ELISA'),
that could at least partially overcome these problems have been
described, but have to be optimised and validated for the diagnosis
of FMD. Another diagnostic approach that should be evaluated is
the isotype-specific detection of antibodies to FMD in oesophageal-pharyngeal
fluid.
Coordinator
Bernd HAAS
Federal Research Centre for Virus Diseases of Animals
Paul-Ehrlich-Straße 28
D-72078 Tübingen
Tel.: +49 707 196 72 52
Fax: +49 707 196 73 05
E-mail: bernd.haas@tue.bfav.de
Partners
- Kris DE CLERCQ
Centrum voor Onderzoek in Diergeneeskunde en Agrochemie
Afdeling epizootische ziekten
Groeselenberg 99
B-1180 Brussels
Tel.: +32 2 375 44 55
Fax: +32 2 375 09 79
- Karl-Johan SORENSEN
Danish Veterinary Institute for Virus Research
Lindholm
DK-4771 Kalvehalve
Tel.: +45 55 86 02 31
Fax: +45 55 86 03 00
- Emiliana BROCCHI
Instituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna
National FMD Laboratory
Via A Bianchi N7
I-25125 Brescia
Tel.: +39 030 22 90 310
Fax: +39 030 22 90 310 or +39 030 22 56 13
- Remco SCHRIJVER
Institute for Animal Science and Health (ID-Lelystad)
Houtribweg 39
P.O. Box 65
NL-8200 AB Lelystad
Tel.: +31 320 23 86 10
Fax: +31 320 23 86 68
- Francisco SOBRINO
Instituto Nacional de Investicacion y Tecnologia Agraria y Alimentaria
Centro de Investigacion en Sanidad Animal CISA-INIA
E-28130 Valdeolmos
Tel.: +34 916 20 23 00
Fax: +34 916 20 22 47
- Paul KITCHING
Institute for Animal Health
Pirbright Laboratory
Ash Road
UK-GU24 ONF Pirbright Woking
Tel.: +44 1483 23 24 41
Fax: +44 1483 23 26 21 or +44 1483 23 24 48
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