WORLD TRADE
ORGANIZATIONG/SPS/GEN/145/Add.3
9 March 2001
(01-1165)
Committee on Sanitary and Phytosanitary Measures Original:  English/
French/
Spanish
CONTINUED EXAMINATION OF DOCUMENT G/SPS/13
PROCEDURE TO MONITOR
THE PROCESS OF INTERNATIONAL HARMONIZATION
Communication from the Office International des Epizooties
Addendum
The following communication was received from the Office international des épizooties
(OIE) on 6 March 2001.
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1. The International Animal Health Code Commission of the Office International des Epizooties
(OIE) met at the OIE headquarters from 22 to 26 January 2001. During the meeting, the Commission
continued its examination of matters concerning the OIE raised in the document entitled "Procedure to
monitor the process of international harmonisation", reference number G/SPS/13.
A. CHICKEN MEAT AND INFECTIOUS BURSAL DISEASE
2. At the request of the Code Commission, the OIE convened an Ad hoc Group on infectious
bursal disease on 11 and 12 January 2001. The experts in this Group were given the task of providing
scientific advice on five questions from the Code Commission relating to the possible transmission of
the infectious bursal disease virus in chicken meat, and to determine areas in which additional
scientific research was needed so as to improve on the existing level of knowledge on the disease.
3. When it met at the end of January 2001, the Code Commission took note of the report of the
Ad hoc Group on infectious bursal disease, and requested the Director General of the OIE to inform
the WTO SPS Committee of the replies given by the experts to its questions (see Annex 1) and the
areas in which they considered that additional research was required (see Annex 2).
4. As the experts also prepared a new draft chapter on infectious bursal disease during their
meeting, the Code Commission decided to submit it for comment to the Delegates of OIE Member
Countries. This draft will remain a restricted document until it has been presented to the OIE
International Committee at the next General Se ssion (May 2001). The Code Commission will decide
during its future meetings whether the draft chapte r can be presented to the International Committee
for adoption in May 2002, taking into account the observations and requests for amendments receivedin the meantime from Member Countries.G/SPS/GEN/145/Add.3
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5. It should be pointed out that the opinions and proposals given in the appendices were
formulated by experts at the request of the OIE. Insofar as they have not been adopted by the OIE
International Committee, they must be considered to reflect only the views of these experts and not
the views of the OIE.
6. Furthermore, as it is not the role of the OIE to conduct research itself, it is hoped that in the
near future countries will show an interest in pr oviding the necessary support for the research to be
carried out.
B. FREQUENCY OF HEALTH CONTROLS TO BE CARRIED OUT ON BULLS AT ARTIFICIAL
INSEMINATION CENTRES
7. The Code Commission conducted a fresh examination of the two draft appendices on bovine
semen submitted for comment to OIE Member Countries. It adopted a proposal made by one of the
countries to combine these texts to form a single Annex. The Commission clarified the sanitaryconditions to be met by bulls before entry into artificial insemination centres and the general
organisation of these centres into different sectors.
8. The new draft Annex will be submitted to the OIE International Committee for adoption next
May.
9. The Code Commission then intends to begin another task aimed at ensuring consistency
between the provisions of the Annex and those of ar ticles relating to bovine semen in the chapters of
the International Animal Health Code  that deal with animal diseases.
C. C
ERTIFICATE OF ORIGIN OF ANIMALS
10. The information on this point given in document G/SPS/GEN/145/Add. 2 remains valid.G/SPS/GEN/145/Add.3
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ANNEX 1
REPLIES FROM THE EXPERTS TO THE QUESTIONS PUT
BY THE CODE COMMISSION
1. What is the probability of finding infectious bursal disease virus in fresh meat obtained
from chickens that were healthy at the time of slaughter?
The experts provided information on the virus titres found in various tissues, based primarily
on data quoted or included in Import Risk Analysis  reports from an OIE Member Country. According
to this data, the very virulent virus could only be detected in muscle of experimentally infected SPFchickens at seven days after infection, but could not be detected at day 14. In another study the classic
serotype 1 virus was found in muscle tissues up to four days but not at seven days post-infection.
However, the study quoted in the risk assessment reported that the virus was detected in the bursa of
Fabricius up to 28 days. In another study a variant serotype 1 virus was detected in the bursa only up
to 21 days.
The experts consider that the use of SPF birds in the virus persistence studies referred to in
the Import Risk Analysis reports does not represent th e situation in the poultry industry, as almost all
commercial birds are exposed to either the field or vaccine virus and therefore immune. Consequently
the virus is probably only present in the carcases of immune birds for short periods if at all: one of theexperts reported that an intermediate vaccine virus was not detected in the bursa of commercial birds
at seven and fourteen days after vaccination (data submitted for publication).
The experts recommended that the work quoted in the Import Risk Analysis should be
published in a peer-reviewed publication.
The bursa of Fabricius is the target organ where the highest virus titre is found. The Import
Risk Analysis reported that 30 per cent of the carcasses sampled after slaughter still contained some
bursal tissue. The experts stated that chicken products such as legs, thighs, breasts and wings would
not pose a significant risk, unless they contain some bursal tissues. In whole carcasses, there is a
potential for viral presence if bursal tissues are present. Studies on the feasibility of complete removal
of bursal tissues during slaughter should be encouraged. If technically and economically feasible, theresulting processes should be adopted.
The experts are of the opinion that certification of absence of clinical signs is not sufficient to
ascertain absence of virus, as some birds may be at the viremic phase before appearance of clinical
signs when slaughtered or some virus strains will not induce clinical signs.
Vaccination has been used successfully worldwide to control disease. Effective vaccination
practices should lower the risk of virus being found in poultry products from immune birds.
A combination of maintaining adequate immunity in meat producing flocks plus slaughter
processes or selection of parts to prevent the inclusion of bursal tissues in exported products would
decrease significantly the risk of IBDV transmission. Consequently, the presence of antibody in flocks
of origin should not be viewed as a negative factor for international trade.
It is important that the vaccination strategies ensure avoidance of residual vaccine virus
infectivity in poultry products.
The experts discussed the potential for transmission from imported IBDV infected meat to
chickens. So far, there is no documented evidence of such transmission.G/SPS/GEN/145/Add.3
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2. What is the effect, if any, of refrigeration a nd freezing on the survival time of the virus
in chicken meat?
There is no significant decrease of virus titre by refrigeration or freezing.
3. Are there strains with differing degrees of virulence and, if so, do the answers to the
previous two questions depend on the degree of virulence?
There are significant differences in virulence of field as well as vaccine strains. The
unpublished data in the Import Risk Analysis would indicate that both a classical virus and a very
virulent virus persisted in muscle tissue up to seven days after experimental exposure. Again theexperts recommended that the relevant studies be published in peer-reviewed publications.
4. What are the determining factors for a country to decide whether or not to vaccinate
against infectious bursal disease?
Vaccination combined with effective sanitary measures is practised worldwide because of
widespread occurrence of pathogenic viruses in commercial poultry. The decision to vaccinate
commercial poultry is the consequence of the demonstration of clinical or immuno-suppressive
disease. The vaccination strategies used are dependent on the virulence of the strains circulating in the
country considered.
5. If there are strains that differ in virule nce, do they require different vaccination
strategies?
See previous point.G/SPS/GEN/145/Add.3
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ANNEX 2
TOPICS RELATING TO THE INFECTIOUS BURSAL DISEASE ON WHICH
ADDITIONAL SCIENTIFIC RESEARCH IS NEEDED
1. Study of the tissue distribution and persistence of the different pathotypes of the virus in the
presence of different levels of antibodies simulating commercial conditions.
2. Development of processing techniques to ensure complete removal of bursal tissue after
slaughter.
3. Study of effective vaccination schedules to avoid the presence of both field and vaccine
viruses in carcasses at slaughter.
4. Development of sensitive procedures for det ection of infectious IBDV in meat products.
5. Development of virulence markers and standardized protocols to differentiate IBDV
pathotypes.
6. Development of practical field monitoring procedures for IBDV infection.
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