D4478.PDF

65 SG/12/CS2 A
Original: English
September 1996
REPORT OF THE MEETING OF THE OIE STANDARDS COMMISSION
Paris, 10-13 September 1996
_______
The OIE Standards Commission met at the OIE headquarters from 10 to 13 September 1996. Dr J. Blancou,
Director General of the OIE, welcomed the members of the Commission and the other participants. He
emphasised the importance placed by the International Committee on the programme of standardisation, and
also the usefulness of the network of Reference Laboratories and Collaborating Centres. Dr Blancou mentioned
that the information sheets on List A diseases had also been well received by Member Countries.
Prof. M. Truszczynski, President of the Standards Commission, thanked Dr Blancou for his welcome. The
Agenda and List of Participants are given in Appendices I and II, respectively.
1.
OIE Reference Laboratories
a)
New applications for Reference Laboratory and Collaborating Centre status
The Commission reviewed the documentation supporting the following applications for OIE
Reference Laboratory status, and recommended that they should be added to the list of Reference
Laboratories:
Dourine:
Federal Institute for Consumers Health Protection and Veterinary
Medicine, Berlin, Germany.
Name of expert: Dr C. Staak.
Enzootic bovine leukosis:
National Veterinary Institute, Department of Virology, Uppsala, Sweden.
Name of expert: Dr K. Klintevall.
Infectious bursal disease:
Food Animal Health Research Program, Ohio Agriculture Research and
Development Center, Ohio State University, Wooster, Ohio, United
States of America (USA).
Name of expert: Dr Y.M. Saif.
The Standards Commission noted the recommendation from the 3rd Conference of the OIE Regional
Commission for the Middle East that a Reference Laboratory should be designated in the region for
peste des petits ruminants (PPR). It was remarked that there are already three OIE Reference
Laboratories for PPR. The Standards Commission emphasised that the activities of OIE Reference
Laboratories are not limited to particular regions. Nevertheless, any new applications would be
carefully considered.
Other proposals were discussed, and receipt of formal applications and supporting documents are
awaited.
b)
Updating the list of Reference Laboratories
The following changes to named experts at OIE Reference Laboratories have been notified to the
OIE. The Commission recommends their acceptance:
Foot and mouth disease:
Dr S. Dudnikov to replace Dr Z. Antonovich at the All-Russian
Research Institute for Animal Health, Vladimir, Russia.
Vesicular stomatitis:
Dr B. Schmitt to replace Dr M. Frey at NVSL1, Ames, USA.
Bluetongue:
Dr D. Alstad to replace Dr J. Pearson at the NVSL, Ames, USA.
African swine fever:
Dr L.A. Thomas to replace Dr C. Mebus at the NVSL, Plum
Island, USA.
Classical swine fever:
Dr R.A. Heckert to replace Dr G. Dulac at the Animal Diseases
Research Institute, Nepean, Canada.
Aujeszky’s disease:
Dr B. Schmitt to replace Dr M. Frey at the NVSL, Ames, USA.
Dr A.T.J. Bianchi to replace Dr T.G. Kimman at the Institute for
Animal Science and Health (ID-DLO), Lelystad, The
Netherlands.
Leptospirosis:
Dr D. Miller to replace Dr L.A. Thomas at the NVSL, Ames,
USA.
Contagious equine metritis:
Dr D. Miller to replace Dr L.A. Thomas at the NVSL, Ames,
USA.
Equine encephalomyelitis:
(Eastern/western & Venezuelan)
Dr D. Alstad to replace Dr J. Pearson at the NVSL, Ames, USA.
Dr R.L.Witter had asked that the Avian Disease and Oncology Laboratory, East Lansing, Michigan,
USA, be removed from the list as OIE Reference Laboratory for Marek’s disease, although he would
remain available for ad hoc queries from Member Countries.
c)
Update on annual reports from the Reference Laboratories
The Commission noted explanations received from several Reference Laboratories as to why annual
reports had not been sent to the OIE, generally due to changes in personnel or lack of relevant
activities.
1
2
NVSL: National Veterinary Services Laboratories
Standards Commission/September 96
2.
International standardisation of diagnostic tests and vaccines
a)
Progress on standardisation of diagnostic tests
LIST A DISEASES
i)
Foot and mouth disease (serology) - Coordinator Dr A. Donaldson
Although it was understood that the standardisation programme was progressing, no recent
report had been received from the programme co-ordinator. It was reported from the OIE
Collaborating Centre at Seibersdorf that some local variations in standard test protocol had
been agreed following regionalisation of production of test kits. An external quality assurance
programme had been initiated among laboratories participating in the FAO/IAEA2 programme.
ii)
Peste des petits ruminants - Coordinator Dr P.C. Lefèvre
Dr P.C. Lefèvre (OIE Reference Laboratory − CIRAD-EMVT3) reported that the candidate
standard sera had been sent to other Reference Laboratories for validation, but results had not
been returned.
iii)
Contagious bovine pleuropneumonia - Coordinator (a) Dr R. Geiger (b) Dr J.L. Martel
(a)
A preliminary report on the evaluation of the monoclonal antibody-based enzymelinked immunosorbent assay (ELISA) kit had been submitted by Dr R. Geiger, Joint
FAO/IAEA Division, Vienna. The Commission looked forward with interest to
receiving the final report.
(b) No update had been received on the preparation of OIE Standard Sera.
iv)
Bluetongue - Coordinator Dr J. Pearson
No further progress to report.
v)
African horse sickness - Coordinator Dr J.M. Sánchez-Vizcaíno
No further progress to report.
vi)
Classical swine fever - Coordinator Dr S. Edwards
Dr S. Edwards reported that candidate standard sera had been prepared, irradiated and freezedried. These would be distributed to other Reference Laboratories during the next few weeks
for further evaluation. He also drew the Commission’s attention to a long-standing WHO4
standard serum - 'Anti-swine fever serum, 1st Standard 1963'. Although this is over 30 years
old, it is still available from the FAO/WHO International Laboratory for Biological Standards,
Weybridge, United Kingdom (UK). It was noted that this was originally prepared principally
for standardisation of vaccine preparations. It has a very high neutralisation titre and is
therefore probably not particularly useful as a standard serum for diagnostic serological tests.
The Commission saw little merit in perpetuating the arbitrary term 'International Units' which
is quoted by WHO, but is not in common usage.
2
FAO/IAEA: Food and Agriculture Organization of the United Nations/International Atomic Energy Agency
3
CIRAD-EMVT: Centre de coopération internationale en recherche agronomique pour le développement/Département
d'élevage et de médecine vétérinaire des pays tropicaux
4
WHO: World Health Organization
Standards Commission/September 96
3
LIST B DISEASES
vii)
Rabies - Coordinator Dr M. Aubert
An update was received from the OIE Reference Laboratory at CNEVA5, Nancy, France. The
candidate canine standard serum had been freeze-dried, and aliquots had been distributed to
27 laboratories. These had participated in training courses for the fluorescent antibody virus
neutralisation (FAVN) test held at the Reference Laboratory. The results so far were in
agreement, but not all had yet been received. It appeared that the FAVN results were more
reproducible than those given by the rapid fluroescent focus inhibition test (RFFIT) procedure.
It was anticipated that a report would be available towards the end of 1996.
viii)
Brucellosis - Coordinator Mr A. MacMillan
A preliminary report on the evaluation of the candidate standard sera for the ELISA had been
submitted by Mr A.P. MacMillan. The Commission looked forward with interest to receiving
the final report.
ix)
Enzootic bovine leukosis - Coordinator Mr M. Dawson
Mr M. Dawson reported that suitable sera and milk had been obtained from bovine spongiform
encephalopathy-free countries, and had been irradiated. Evaluation of test aliquots following
freeze-drying and reconstitution was in progress.
x)
Equine influenza - Coordinator Dr J. Mumford
Dr J. Mumford reported that post-infection antisera to A/equine/2/Newmarket/1/93 (H3N8)
and A/equine/2/Newmarket/2/93 had been prepared and were being freeze-dried by the
European Pharmacopoeia. Samples would be sent to other Reference Laboratories for
evaluation.
xi)
Equine viral arteritis - Coordinator Dr P. Timoney
Dr P. Timoney reported that candidate standard sera had been prepared and were in the
process of distribution to other Reference Laboratories for evaluation.
A letter had been received from the European Federation of Thoroughbred Breeders’
Associations expressing the Federation’s concern over the lack of international standardisation
for equine viral arteritis serological and virus isolation tests. The Commission is well aware of
the importance of these topics, and a reply was drafted outlining the current programme of
standardisation being undertaken by the OIE Reference Laboratories.
b)
Guidelines for laboratory proficiency testing
The Commission finalised the text of the guidelines for laboratory proficiency testing (Standards
Commission report for February 1996) taking into account comments received from Member
Countries. The guidelines are shown in Appendix III and will be incorporated in due course into a
booklet of guidelines relating to standardisation of procedures and evaluation of laboratories.
5
4
CNEVA: Centre national d'études vétérinaires et alimentaires
Standards Commission/September 96
c)
Report of the expert surveillance panel on equine influenza vaccine strain selection
The expert surveillance panel had met in May 1996 to review new information on epidemiology,
vaccine performance in the field, and antigenic and genetic characterisation of new equine influenza
isolates. It was concluded that the previous recommendations for vaccine strains were still valid. The
Commission suggested that the report should be published in the OIE Bulletin, as recommended in the
report of the Standards Commission for September 1995.
3.
Finalisation of the OIE Manual (third edition)
For this session, the Commission was joined by the Consultant Editor, Dr G.A. Cullen.
The Manual will be published in a new format − A4 size with double column text. This will facilitate
handling of the volume which has considerable additional text since the previous edition.
Only three remaining disease chapters were awaiting modifications following Member Country comments.
These were expected within the next few weeks. Most of the remaining chapters have now completed the
finalisation process; this includes a final check by the authors, editorial proof-reading and perfecting the
layout. The Commission spent a considerable time discussing detailed points of clarification on individual
disease chapters, which will be dealt with by the editorial team.
A Foreword was drafted for the new edition of the Manual, and the glossary and list of abbreviations were
checked. The final drafts of the introductory chapters were reviewed.
Concerning the table of prescribed tests, it was agreed that the column headed 'other tests' has little value
because the primary purpose of this table is to identify tests prescribed for use in international trade, as
required by the International Animal Health Code, with some possible alternative tests which could be
used by bilateral agreement. Many other tests are described in the Manual which have applications in
diagnosis and surveillance, but are not required for international trade. Accordingly, the category of 'other
tests' will not be included in the summary table in future. For clarity, diseases for which there are no
prescribed or alternative tests will be listed in the table with a blank entry.
The Commission discussed the definition of fowl cholera (avian pasteurellosis) which poses some
problems due to the widespread occurrence of low virulence strains of the organism. This may have
implications for both Manual and Code, and could not be resolved in time for the third edition. It will be
addressed by the Commission on a future occasion.
4.
Liaison with the Animal Health Code Commission
a)
Avian chlamydiosis
Following advice from an expert in this area, the Standards Commission advised the Code
Commission that the current diagnostic tests for avian chlamydiosis had certain limitations. An
extension of the coverage of the Code chapter on avian chlamydiosis to other avian species would
create difficulties for regulatory authorities, and it was agreed that for the present, the chapter should
remain confined to psittacines. The Standards Commission agreed to monitor the development of
improved diagnostic tests, and to keep the Code Commission informed.
b)
Risk analysis for veterinary biologicals
The Commissions discussed the draft Code chapter on this topic, together with comments received
from Member Countries. It was agreed that this is a difficult subject on which to reach a consensus
view, but that its importance merited the effort necessary to achieve one. It was agreed that a revised
text should be produced with a specific focus on vaccines.
Standards Commission/September 96
5
c)
Enzootic bovine leukosis
The Standards Commission confirmed its view, previously stated, that polymerase chain reaction
(PCR) tests for the detection of bovine leukosis pro-virus in tissues are very promising, but are still of
limited availability and lack international standardisation. Accordingly, such tests could not yet be
recommended for use for international trade purposes.
d)
Contagious caprine pleuropneumonia
The Standards Commission informed the Code Commission that the currently accepted nomenclature
for the causal organism of contagious caprine pleuropneumonia is Mycoplasma capricolum
subspecies capripneumoniae.
e)
Scrapie
The question was discussed of bioassay of mesenteric lymph nodes as a means of confirming the
absence of scrapie in a flock. The Standards Commission commented that although bioassay was
referred to in the new edition of the Manual, it is not considered appropriate for this purpose.
f)
Equine influenza
The Standards Commission recommended that virus isolation is inappropriate as a diagnostic method
during quarantine.
g)
Biosecurity for animal pathogens
The Standards Commission agreed to provide comments on the draft Code chapter. It had been agreed
that biosecurity as an animal health risk would be dealt with in the Code, while the control of human
health risk, particularly to laboratory staff, was covered in introductory chapter I.5. in the Manual.
h)
Tests relevant to trade in semen
The Standards Commission confirmed that there would be chapters on bovine viral diarrhoea and on
border disease in the forthcoming edition of the Manual, including diagnostic tests suitable for
screening animals as semen donors. The Code Commission would, if possible, like such tests to be
identified as 'prescribed'. This had already been done for bovine viral diarrhoea, and would be
initiated for border disease with a view to obtaining approval from the next meeting of the
International Committee.
i)
Infectious bovine rhinotracheitis/infectious pustular vulvovaginitis
The Code Commission queried whether consideration should be given to the use of marker vaccines
in herds which are free of infectious bovine rhinotracheitis/infectious pustular vulvovaginitis. The
Standards Commission suggested that more information was first needed on the application of such
vaccines to control schemes. Furthermore, it was suggested that as more data are available on the use
of such vaccines for Aujeszky’s disease in pigs, it might be appropriate for the Code Commission to
review that chapter first, as a model for similar situations with other diseases.
j)
Avian influenza
The Standards Commission drew attention to the OIE definition of 'highly pathogenic avian influenza'
which was already included in the Manual, but which had not yet been updated in the Code.
6
Standards Commission/September 96
5.
List of prescribed and alternative tests
The list of prescribed and alternative tests would be printed in the third edition of the Manual including
modifications approved by the International Committee up to and including May 1996. New
recommendations are that, as prescribed tests for trypanosomosis and for surra are not required by the
Code for international trade purposes, they should be removed from the list of prescribed and alternative
tests.
It is proposed that agent identification for border disease be allocated the status of prescribed test for
screening of sheep as potential semen donors.
6.
Other business
a)
Report of WHO Collaborating Centre on prevention and control of zoonoses
The Commission noted with interest the report received by OIE on the activities of the above WHO
Collaborating Centre located at the All-Russian Research Institute of Experimental Veterinary
Medicine, Moscow, Russia.
b)
Report of a WHO/FAO/OIE consultation on animal tuberculosis vaccines
The Commission noted the implications mentioned in this report of the possible impact on tuberculin
tests used for international trade, should vaccines be used for control of tuberculosis in animals.
c)
OIE satellite symposium at the 15th International Pig Veterinary Society Congress
A proposal was discussed that OIE should organise a satellite symposium on classical swine fever at
the end of the International Pig Veterinary Society (IPVS) congress to be held in Birmingham, UK, in
July 1998. The Commission is in favour of this proposal, and suggested various items for the
programme. The Commission of the European Communities will also be asked whether they would be
interested in combining the symposium with the annual meeting of European classical swine fever
laboratories.
d)
Meeting on Harmonisation of Veterinary Biologics in the Americas
The Commission were pleased to note the contribution of OIE to this meeting, to be held in Campo
Grande, Brazil, in October 1996. It was noted that Dr R. Reichard would be representing OIE.
e)
Meetings attended by members of the Standards Commission
Prof. M. Truszczynski attended the 8th Symposium of the WAVLD6, held in Jerusalem, Israel, in
August 1996, when he presented a paper entitled 'Progress on harmonisation of diagnostic tests of
Lists A and B diseases as a result of the activity of the OIE Standards Commission'.
Dr J.E. Pearson presented a talk to the USDA7 Veterinary Services Managers Conference entitled
'The impact of OIE on the Veterinary Services of USDA'.
Dr S. Edwards attended, on behalf of OIE, an FAO workshop, held in Budapest, Hungary, in April
1996, for delegates from Eastern Europe on 'Upgrading Veterinary Vaccines and Biologicals' where
he gave a lecture on 'Standardisation of Veterinary Vaccines and Biologicals: The role of OIE'.
6
7
WAVLD: World Association of Veterinary Laboratory Diagnosticians
USDA: United States Department of Agruiculture
Standards Commission/September 96
7
Dr Edwards also attended the 14th Symposium of the World Association of Veterinary
Microbiologists and Specialists in Infectious Diseases (WAVMI), held in Edinburgh, UK, from 3 to 5
July 1996, where he presented a paper on the same topic.
Dr Edwards attended the 1st European Symposium on Equine Viral Arteritis, held in Utrecht, The
Netherlands, on 7 May 1996, where he presented a paper on 'Antigenic variation in equine arteritis
virus', as well as describing briefly the role of OIE in standardisation of diagnostic tests. The meeting
was also attended by Dr P.J. Timoney and Dr D.J. Paton, as representatives of the OIE Reference
Laboratories for EVA. Drs Timoney and Edwards have prepared a summary report of the meeting
which is given in Appendix IV.
f)
Collaboration with the World Association of Veterinary Laboratory Diagnosticians
The Commission responded to a letter from Dr E. Bogin, President of the WAVLD, indicating the
willingness of OIE to develop collaborative activities in the area of infectious disease diagnosis.
g)
OIE Disease Cards on List A diseases
The disease cards had been sent to most Member Countries for distribution and comment, and the
remaining Member Countries would receive them shortly. The sheets were accompanied by a simple
questionnaire, for which the preliminary responses were as follows:
Questions:
Yes
No
Do you consider the sheets to be of use to your services?
36
1
Do you consider the sheets could be improved?
16
19
Are there any List B diseases for which you feel a sheet would be useful?
32
6
The detailed comments on how the sheets could be improved, and on the List B diseases for which
additional sheets might be produced, will be considered at a future meeting of the Commission when
further replies have been received. Initial responses indicated greatest interest for List B in bovine
spongiform encephalopathy, rabies, brucellosis, and anthrax.
h)
Proposed collaboration on anthrax
The Commission noted a proposal to form a European collaborative group on anthrax. While OIE is
pleased to be informed of this important initiative, it was agreed that other priorities would prevent
active OIE participation at present.
i)
Meeting on Good Laboratory Practice (GLP) for veterinary laboratories
The members of the Commisssion attended a meeting at the offices of OECD8 in Paris to discuss the
need for Good Laboratory Practice (GLP) accreditation in veterinary diagnostic laboratories in the
international arena. The meeting was also attended by representatives of OECD, FAO, the
FAO/IAEA Joint Division, Telos bioinformatics (on behalf of the AVIS consortium), various national
and international veterinary laboratories, and experts in GLP accreditation. It appears to the
Commission that there should be further discussion among OIE, OECD and other international
organisations on the possibility of developing a framework for international mutual recognition of
national GLP standards in the field of animal health. An informal working group will meet again, on
which Dr Edwards will represent the Standards Commission.
8
8
OECD: Organisation for Economic Co-operation and Development
Standards Commission/September 96
7.
Future activities of the Standards Commission
The agenda for the next meeting should include the following:
1.
OIE Reference Laboratories
a) New applications for Reference Laboratory status
b) Updating the list of Reference Laboratories and experts
c) Annual reports from Reference Laboratories and Collaborating Centres
2.
Progress on international standardisation of diagnostic tests and vaccines
3.
List of prescribed and alternative tests
4.
OIE Manual
5.
Preparation of booklet of guidelines
6.
OIE Information Sheets on Lists A and B diseases
7.
Liaison with other Commissions
8.
Any other business
The proposed date for the next meeting of the Standards Commission would be from: 26 to 28 February
1997.
Standards Commission/September 96
9
10
Standards Commission/September 96
Appendix I
MEETING OF THE OIE STANDARDS COMMISSION
Paris, 10-13 September 1996
_________
Agenda
1.
OIE Reference Laboratories
a)
b)
c)
2.
New applications for Reference Laboratory and Collaborating Centre status
Updating the list of Reference Laboratories
Update on annual reports from the Reference Laboratories
International Standardisation of Diagnostic Tests and Vaccines
a)
b)
Progress on standardisation of diagnostic tests
OIE Guidelines for laboratory proficiency testing
3.
Finalisation of the OIE Manual (third edition)
4.
Liaison with the Animal Health Code Commission
5.
List of prescribed and alternative tests
6.
Other business
7.
Future activities of the Standards Commission
Standards Commission/September 96
11
12
Standards Commission/September 96
Appendix II
MEETING OF THE OIE STANDARDS COMMISSION
Paris, 10-13 September 1996
_______
List of participants
MEMBERS
Prof. M. Truszczynski
(President)
Director General
National Veterinary Research Institute
57 Partyzantow St.
24-100 Pulawy
POLAND
Tel: (48.81) 86.32.70
Telex: 642401 IWET PL
Fax: (48.81) 86.95
Dr J.E. Pearson
(Vice President)
National Veterinary Services
Laboratories (NVSL)
APHIS, USDA
P.O. Box 844,
Ames, Iowa 50010
USA
email: [email protected]
Tel: (1-515) 239.84.05
Fax: (1-515) 239.83.97
Dr S. Edwards
(Secretary General)
Weybridge Central Veterinary Laboratory
New Haw, Addlestone
Surrey KT15 3NB
UNITED KINGDOM
e-mail: [email protected]
Tel: (44-1) 932 34.11.11
Fax: (44-1) 932 34.70.46
OIE COLLABORATING CENTRE
OIE CONSULTANT EDITOR
Dr Mark Robinson
FAO/IAEA Centre for ELISA and Molecular
Techniques in Animal Disease Diagnosis
International Atomic Energy Agency
Wagramerstrasse 5
P.O. Box 100
A-1400 Vienna
AUSTRIA
Tel: (43-1) 2060.26053
Fax: (43-1) 20607
Dr G.A. Cullen
Birchbrook
22 Silver Birch Close
Woodham
Weybridge
Surrey KT15 3QW
UNITED KINGDOM
Tel: (44-1) 932 34.66.46
Fax: (44-1) 932 35.06.93
OTHER PARTICIPANT
Dr P.F. Wright
Agriculture and Agri-Food Canada
c/oDepartment of Animal Science
University of Manitoba
Winnipeg
Manitoba R3T 2N2
CANADA
email:[email protected]
Tel: (204) 984 1007
Fax: (204) 275 0402
OIE CENTRAL BUREAU
Dr J. Blancou
Director General
12 rue de Prony
75017 Paris
France
Tel: 33 - (0)1 44.15.18.88
Fax: 33 - (0)1 42.67.09.87
E-mail: 100765,[email protected]
Standards Commission/September 96
Dr R. Reichard
Head, Scientific and Technical Department
email: [email protected]
Miss S. Linnane
Scientific Editor
Scientific and Technical Department
13
Appendix III
OIE GUIDELINES FOR LABORATORY PROFICIENCY TESTING
1.
Introduction
1.1 Purpose
This document provides guidelines for evaluation of laboratory capability to conduct diagnostic tests for
infectious diseases and is to supplement the OIE Guidelines for the Evaluation of Veterinary Services
(Rev. sci. tech. Off. int. Epiz., 1993, 12 (4), 1291-1313).
1.2 Scope
These guidelines are intended for use by OIE Member Countries as part of the evaluation of laboratories
that are carrying out tests to qualify animals and animal products for international movement. These
guidelines should be used in conjunction with the OIE Guidelines for Laboratory Quality Evaluation for
overall assessment of laboratory quality and capability.
This guide is based on the relevant requirements of the ISO9 9000 series of standards and ISO/IEC10
Guides 25 and 43.
1.3 Interlaboratory test comparisons
Interlaboratory test comparisons may be undertaken for a variety of reasons which may include:
(i)
Determining a laboratory’s capability to conduct specific diagnostic tests,
(ii)
Checking or certifying the performance of individual operators,
(iii)
Checking or certifying the calibration of instrumentation,
(iv)
Harmonising existing test methods,
(v)
Evaluating new test methods,
(vi)
Assigning values and ranges to standard materials,
(vii)
Resolving interlaboratory differences.
1.4 Proficiency testing
When an interlaboratory test comparison is conducted for the express purpose of determining a
laboratory’s capability to conduct specific diagnostic tests, i.e. 1.3 (i) above, it is referred to as proficiency
testing. Proficiency testing is an integral part of laboratory accreditation programmes.
Proficiency testing schemes are based on defined sets of highly characterised test materials which are
sometimes referred to as check sample panels. These panels are simultaneously sent to participating
laboratories for testing. The results are collected and analysed against assigned values in order to
determine the capability of a participating laboratory to conduct a diagnostic test and produce correct
results.
9
10
ISO: International Organisation for Standardisation
IEC: International Electrotechnical Commission
Standards Commission/September 96
15
1.5 Accreditation
An accreditation programme is a formal process for recognition of laboratory quality and capability by an
independent authority. It requires that laboratories successfully participate in an accreditation programme
on an ongoing basis in order to maintain their recognition status. The independent authority awards or
denies recognition based on stipulated requirements for quality and capability.
In the initial stage of accreditation, laboratories are required to demonstrate a specified and sustainable
level of quality. Ideally this would involve compliance with ISO 9000 and ISO/IEC Guide 25 General
Requirements for the Competence of Calibration and Testing Laboratories (1990) in order to qualify for
entry into the programme. However, it is recognised that in many circumstances such a high level may be
difficult to achieve for a variety of reasons. The OIE Guidelines for Laboratory Quality Evaluation were
prepared in order to establish a minimum acceptable level of quality.
The second stage of accreditation entails regularly scheduled proficiency testing for the evaluation of a
laboratory’s capability to conduct specific diagnostic tests. As proficiency testing schemes are a form of
interlaboratory comparison, they must involve two or more laboratories. There is no agreed standard for
proficiency testing in veterinary diagnostics, although several schemes are in operation at international
and national levels. The present guidelines have been prepared to be used in conjunction with the OIE
Guidelines for Laboratory Quality Evaluation. Together, these guidelines form an acceptable basis for a
quality assurance programme.
2.
Authority and recognition
Accreditation programmes and proficiency testing schemes should be operated by an independent authority in
order to prevent any bias in the award or denial of recognition.
Participation in an international accreditation programme and proficiency testing scheme should be voluntary.
Lack of participation or failure to achieve recognition should not prevent a laboratory from conducting
diagnostic tests or a country from entering into trade agreements.
Participation and recognition status should be made available by the independent authority to trading partners
only at the request of or with the consent of the participating laboratory or country authority.
Such a programme and scheme may involve a cost to the participating laboratories for this service.
3.
Organisation and management
Details of the proficiency testing scheme and its purpose, eligibility of participating laboratories and disposition
of the results should be documented by the coordinating organisation to ensure the protection of proprietary
rights and confidential information.
A programme manager should have overall responsibility for the operation, quality and security of the
proficiency testing scheme.
It is also the responsibility of the programme manager to ensure that laboratories involved in the production of
test materials are compliant with the relevant requirements of the ISO 9000 series of standards and ISO/IEC
Guide 25.
Employees should be free from pressure or inducements that might unduly influence the analysis of proficiency
testing results or the recognition status of the participating laboratory.
Adequate supervision and security should be provided by staff involved in either the production and
distribution of test materials to be used in the proficiency testing scheme or the receipt and analysis of test
results submitted by participating laboratories.
16
Standards Commission/September 96
4.
Standard methods
For the characterisation of test materials to be used in check sample panels, the standard method should meet or
exceed the minimum diagnostic performance characteristics required for eligibility as a prescribed test in the
OIE Manual of Standards for Diagnostic Tests and Vaccines.
The standard test should be calibrated against international standard materials, if these are available.
Participating laboratories should also be encouraged to calibrate their own assays against the same international
standards.
5.
Selection and composition of check sample panel
5.1 General principles
For the purpose of selection of test materials for inclusion in the check sample panel, the initial assessment
of the status and/or reactivity of the sample will be determined by the producing laboratory, using the
standard method.
Acceptance of test materials into the proficiency panel should be based on repeated testing by more than
one analyst conducting multiple runs of the test on different days. Sufficient values should be generated to
assure the unequivocal status of the test material.
The number of test samples that constitute a check sample panel is not well defined. This will be dictated
by the type of analysis to be performed on the results and the numbers required to ensure statistical
validity.
5.2 Serological tests
Irrespective of the type of test, a minimum of three samples should be included:
(i)
An unequivocal strong positive,
(ii)
An unequivocal weak positive,
(iii)
An unequivocal negative.
However, using only three samples of this nature would render the results very predictable after a few
rounds of proficiency testing. It would be advisable, therefore, to add at least two more samples to the
check sample panel which could be varied from one proficiency test round to the next. This would prevent
participating laboratories from anticipating the expected outcome. The additional samples could be
different from the above or replicates of the above or a combination.
Additional requirements for serological test materials are that they:
(i)
Are derived from a single animal or pool of animal sera,
(ii)
Are undiluted, or diluted in negative serum,
(iii)
Are not lipaemic,
(iv)
Do not contain secondary clots,
(v)
Are not contaminated,
(vi)
Have not been repeatedly frozen and thawed,
(vii)
Are free from infectious agents,
(viii) Are of sufficient volume for at least two consecutive proficiency test runs from the same
processing batch, and
Standards Commission/September 96
17
(ix)
6.
Are stable under conditions of processing and transport to participating laboratories for at least two
years.
Statistical analysis for serological tests
6.1 Types of data
The choice of statistical analysis will in part be determined by the type of data generated by the test
method in question. Qualitative data such as ‘positive’, ‘negative’ and/or ‘suspicious’ are somewhat
limited in the statistical procedures which may be applied to them. Quantitative data such as end-point
titres, and semi-quantitative data such as percentage inhibition values are more flexible with respect to the
types of statistical analysis possible.
Irrespective of the type of data to be analysed, it is important that the data from all of the participating
laboratories be compatible. In some cases, this may require that participating laboratories be instructed to
use a specific dilution series or to express their data against a common standard.
6.2 Assigned values
In the initial selection of test materials for the check sample panel, the producing laboratory will have
assigned a preliminary value, range or status to the sample. For qualitative data, the assigned value may be
the only acceptable value. If this is to be the case, then the producing laboratory should verify the status
on a battery of tests to increase the confidence that the assigned value is in fact correct. However, as a
goal, at least 80% of the participating laboratories should obtain the same result in proficiency tests. For
quantitative and semi-quantitative data, the assigned value should be recalculated after proficiency testing
results are submitted, and it should be taken as the mean value after removal of outliers.
6.3 Statistical methods
Many statistical procedures have been applied to interlaboratory comparisons, some being far more
sophisticated than others. As a general rule, the statistics being applied should be valid, straightforward
and meaningful to the participating laboratories.
Frequency analysis is a simple and meaningful method for participating laboratories to see where their
performance lies with respect to the other laboratories in the proficiency testing scheme.
Measures of intra- and interlaboratory variance through repeatability and reproducibility indices will often
provide valuable information on the precision and robustness of the test methods.
Youden analysis is a useful indicator of systematic or random error sources that may be causing problems
in individual laboratories.
7.
Pass/fail criteria
Decision criteria with regards to passing or failing a laboratory on a proficiency test should be clearly
documented. These criteria must take into consideration factors which may vary from one disease to another
and between types of tests. Once established, the criteria must be applied uniformly.
The types of statistical analyses chosen should assist in making pass/fail decisions. Laboratories submitting
results that fall outside ranges established by statistical means should be identified. Results of serological tests
that would potentially lead to a false-negative classification of an infected animal would have to be weighed
against results that would potentially lead to a false-positive classification of a healthy
18
Standards Commission/September 96
animal. In most instances, the former type of error should not be tolerated as it indicates that there is a problem
with diagnostic sensitivity. However, there may be some latitude in awarding a provisional status to
laboratories experiencing problems with diagnostic specificity.
8.
Frequency of proficiency testing
It is recommended that proficiency testing be done on a biannual basis. Depending on the country and disease,
some consideration should be given to peak testing periods. Whenever possible, at least one of the proficiency
tests should be scheduled to coincide with active testing periods.
Twice yearly, provides sufficient time between proficiency tests to undertake any corrective actions which
might prevent a participating laboratory from losing its recognition status.
9.
Laboratory recognition
The criteria for awarding, denying or withdrawing recognition should be clearly documented.
10. Logistics
10.1
Eligibility and acceptance
Eligible laboratories should be sent a comprehensive outline of the quality assurance programme and the
proficiency testing scheme. This outline should include details pertaining to frequency of testing,
commitments and deadlines, methods of data analysis, reporting structure, criteria for recognition,
disposition of results and confidentiality. In addition, a form to be signed and returned to the
coordinating organisation should be included which indicates that the eligible laboratory accepts the
terms and conditions of the programme.
10.2
Notification and shipment of panels
Participating laboratories should be notified at least 1 month in advance of a pending proficiency test.
Notification should also include the projected date and method of shipment of the check sample panel.
Longer notification may be required by those laboratories in countries requiring import permits for the
check sample panels.
Test materials in the check samples should be coded so as not to indicate their expected result. The
coding may be alphabetic or numeric. Each participating laboratory should receive a panel with a unique
set of codes to prevent collusion between laboratories.
All shipments should be by the most expedient and direct method. All shipments should comply with
IATA11 regulations concerning the shipment of biological materials.
Upon shipment, the recipient laboratories should be informed of pertinent details (i.e. method of
shipment, carrier, air-way bill, etc.) in order to facilitate rapid retrieval and clearance of the shipment
upon arrival.
Check sample panels arriving in a damaged or questionable condition should be replaced immediately.
10.3
Testing and return of results
Participating laboratories should be given an adequate volume of test material and adequate time to
complete the testing of the check sample panel to their satisfaction. The panel may be tested more than
once and by more than one person in the participating laboratory. However, only one set of results
should be returned to the coordinating organisation for analysis. Normally, the person responsible for
running the test routinely should be selected to run the check sample panel.
11
IATA: International Air Transport Association
Standards Commission/September 96
19
The check sample panel should be accompanied by a complete set of instructions with respect to
reconstitution, storage and handling, special testing requirements, data expression and deadline for the
submission of results.
Results must be returned in the proper format and on time. Failure to do so could lead to omission from
the round of proficiency testing and loss or downgrading of recognition status.
The coordinating organisation should acknowledge receipt of the results and their acceptance into the
analysis.
10.4
Analysis and reporting
Analysis and reporting should be completed in a timely fashion after the deadline for the receipt of
results.
A general report summarising the results of all of the analyses should be prepared for distribution to all
participating laboratories. Participating laboratories should be randomly assigned a code to ensure
anonymity in the general report. Individual laboratories should be informed of their unique code for this
run of proficiency tests.
Individual laboratories should also receive a summary of their own performance and their recognition
status. This summary should indicate clearly all factors contributing to any change in their status. Where
the status has been downgraded, it is especially important to indicate real or potential causes which may
have contributed to downgrading. In some instances, it may be pertinent to re-issue a second, identical
panel after corrective actions have been taken.
A statement of status may also take the form of an official certificate.
All data, results of analyses and the recognition status of participating laboratories should be kept in
confidence at all times.
11. Disclosure
The primary purpose of these guidelines is to remove trade barriers and not to create them. It would be
expected that participating laboratories having achieved full recognition status may request that official
verification of their status be made available to trading partners from the independent authority or coordinating
organisation. This should only be done at the request of or with the consent of the participating laboratory or
country authority.
20
Standards Commission/September 96
Appendix IV
REPORT OF THE FIRST EUROPEAN SYMPOSIUM ON EQUINE VIRAL ARTERITIS
Utrecht, The Netherlands, May 7, 1996
P.J. TIMONEY12 & S. EDWARDS13
The First European Symposium on Equine Viral Arteritis (EVA) was held in Utrecht, The Netherlands, on 7 May
1996. Some 84 listed delegates representing 14 European countries and the USA attended. The authors of this report,
representing the OIE Reference Laboratories for EVA, were asked by the organisers to present a summary of the
papers and discussions to OIE.
The emphasis of this symposium was primarily on the veterinary medical aspects of EVA, a disease of increasing
concern in many of the member states of the European Union (EU). In bringing together researchers and regulatory
officials from participating countries, it was hoped to facilitate the exchange of information on the current status of
the disease in Europe, and to discuss features of the biology of the causal agent, equine arteritis virus, germane to the
development of improved means of diagnosis, prevention and control of this infection. The lack of uniformity in
diagnostic procedures in current use in many countries and in the interpretation of test results, attest to the need for
discussion of these important issues. This symposium of EVA was especially timely in light of the increasing risk of
the spread of equine arteritis virus infection through the movement of horses and shipment of equine semen within
Europe.
The programme comprised two sessions: (a) eight invited papers on different aspects of the biology, epidemiology,
diagnosis, prevention and control of equine arteritis virus; (b) reviews, by national representatives, of the current
EVA situation in various European countries. Posters addressing a variety of topics relating to equine arteritis virus
were also displayed.
Chaired by Dr P. Rottier (Utrecht, The Netherlands), the morning session commenced with a general overview of
EVA as an emergent disease of international significance given by Dr P. Timoney (Kentucky, USA). He provided an
historical perspective of the disease since it was first defined in 1953, emphasising the limited number of confirmed
outbreaks of the disease in relation to the global ubiquitousness of the causal virus, equine arteritis virus. Major
factors in the epidemiology of this infection were reviewed in detail, including virus shedding patterns during acute
and chronic phases of the infection and how these relate to the principal means of virus transmission. Occurrence of
the carrier state in the stallion was highlighted as perhaps the single most important mechanism ensuring the
continued dissemination of equine arteritis virus among horse populations in Europe and elsewhere. Points of
specific emphasis in discussion of the carrier state were the apparent variability in its occurrence among certain
breeds of horses and in the duration of viral persistence in the reproductive tract of infected stallions. Permanent
clearance of the carrier state does occur in a small percentage of long-term carrier animals. Current prevention and
control programmes against EVA based on controlling the infection in breeding populations of horses have been
successful in preventing outbreaks of virus-related abortion and establishment of the carrier state in stallions.
Selective use of one of two commercially available vaccines against EVA has been an integral component of such
control programmes. The risk of spread of equine arteritis virus infection internationally has escalated with the
increasing frequency of movement of stallions and of fresh-cooled or frozen equine semen, some of which may be
infected with the virus. There is a need for harmonisation of measures for the international control of EVA
which should appropriately come under the aegis of OIE.
Dr A. de Vries (Utrecht, The Netherlands) comprehensively reviewed the molecular biology of equine arteritis
virus. The current taxonomic classification of the virus was discussed, as were its replication strategies and genomic
structure. Information was presented on the membrane topology of the 25 kDa small envelope glycoprotein (GS), the
30-42 kDa large envelope glycoprotein (GL), and the 16 kDa unglycosylated membrane protein (M) of equine
arteritis virus. Whereas the phosphorylated nucleocapsid protein (N) and the envelope glycoprotein (GL) are highly
immunogenic, the unglycosylated membrane protein (M) and the envelope glycoprotein (GS) are poorly so. There is
evidence that the GL ectodomain is an important antigen recognised by neutralising and non-neutralising antibodies
in the horse. Regions of this ectodomain have been shown to induce virus neutralising antibodies in horses. These
features indicate that the GL protein would be an appropriate candidate for the development/further refinement of
diagnostic assays and vaccines against EVA.
Dr E. Chirnside (Newmarket, UK) described the use of recombinant fusion proteins of equine arteritis virus for the
development of an enzyme-linked immunosorbent assay (ELISA) for detecting virus-specific antibodies. Subcloning
12
13
Department of Veterinary Science, 108 Gluck Equine Research Center, University of Kentucky, Lexington,
KY 40546-0099, USA
Central Veterinary Laboratory (Weybridge), New Haw, Addlestone, Surrey KT15 3NB, UK
Standards Commission/September 96
21
of the open reading frame (ORF) 5 and 7 constructs confirmed the presence of major antigenic epitopes between GL
residues 55-98 and within N residues 1-69. An ELISA based on recombinant fusion proteins that included these
residues has been found to be both sensitive and specific for the detection of equine arteritis virus antibodies in the
sera of several species of equid. This rGL ELISA can detect antibodies induced by natural infection or following
vaccination with either commercial vaccine, but cannot differentiate between naturally infected and vaccinated
animals. On comparison with the existing virus neutralisation test, the rGL ELISA detects a higher percentage of
seropositive samples. This may reflect greater sensitivity of the assay or the occurrence of false-positive reactions.
Evidence was presented that the ELISA could detect antibody reactivity in the sera of EVA vaccinated horses some
time after they had reverted to seronegativity in the virus neutralisation test, suggesting that the rGL ELISA may be
the more sensitive assay for the serodiagnosis of equine arteritis virus infection.
Antigenic variation within the GL protein of equine arteritis virus was discussed by Dr S. Edwards (Weybridge,
UK). Although only one serotype of equine arteritis virus is still recognised, considerable antigenic variation has
been found between different virus isolates based on the results of cross-neutralisation tests with conventional
antisera or monoclonal antibodies. Using a panel of mouse monoclonal antibodies raised against the Weybridge
variant of the Bucyrus strain of equine arteritis virus, it was possible to differentiate antigenically distinct strains in
both binding and neutralisation assays among the small group of viruses selected for study. Clear-cut differences
were found among four viruses ostensibly described as the Bucyrus strain of equine arteritis virus, which were
obtained from different sources. The KY-’84 and UK-’93 strains of the virus, however, were unreactive in the same
binding assays. Using polyclonal antisera, the same differences between strains were apparent, although they were
less clear-cut. Exchange of a panel of test sera among selected laboratories engaged in carrying out the virus
neutralisation test confirmed that whereas most laboratories correctly identified positive and negative samples,
significant variation was recorded in the titre of positive samples. It is apparent that the standard strain of equine
arteritis virus used in the virus neutralisation test is of considerable importance in accounting for this variation. The
source of added complement, on the other hand, whether from guinea pigs or rabbits, did not materially affect the
outcome of the test. Based on these findings, greater efforts need to be made to achieve international
standardisation of the virus neutralisation tests in light of its importance in screening horses for international
trade and for diagnostic or control programmes against EVA.
Results of a comprehensive study on the application of a nested polymerase chain reaction (PCR) assay for the
detection of equine arteritis virus in a wide range of clinical and post-mortem specimens were presented by Dr S.
Belak (Uppsala, Sweden). The safeguards needed to ensure against false-negative or false-positive reactions in the
PCR assay were reviewed, especially as they relate to the risk of cross-contamination of samples in the laboratory.
Specimens from cases of natural or experimental equine arteritis virus infection comprising seminal plasma,
nasopharyngeal swab eluates, lymphocytes and tissue specimens were screened in parallel, by attempted virus
isolation in cell culture and by the nested PCR assay. In all but 2 of 77 specimens, there was full agreement between
the results of the two testing procedures. The two samples for which the results were in disagreement were seminal
plasma samples with low infectivity titres close to the detection limit of both systems. The evidence presented
confirmed the reliability of the nested PCR assay for the detection of strains of equine arteritis virus of disparate
geographic origin. The assay has the major advantage of speed when compared with conventional virus isolation in
that it can be completed within 48 hours. As the PCR assay cannot distinguish between infectious and non-infectious
virus, a positive result will not necessarily reflect the infectivity status of a particular horse. In light of its sensitivity,
reliability and short test time, the nested PCR assay should be considered to be an adjunct to virus isolation in cell
culture for the diagnosis of equine arteritis virus infection.
An extensive outbreak of EVA in Spain in 1992 provided the basis for an interesting paper by Dr L. Monreal
(Barcelona, Spain). The source of the outbreak that occurred in a riding establishment near Barcelona was thought to
have been a recently introduced stallion that was acutely infected with the virus. While most affected horses
developed only mild signs of EVA, a small number became more severely ill and exhibited signs of a vesicularerosive stomatitis, a sign not previously reported in cases of this disease. Regardless of clinical severity, all affected
horses recovered within 7-12 days. A notable feature of the outbreak which was confirmed on serological grounds,
was the failure to isolate equine arteritis virus in cell culture from unclotted blood samples taken during the febrile
phase of the illness. Based on serological examination, there was no evidence of intercurrent infection with a range
of other equine viruses at the time of the outbreak.
Dr G. Autorino (Rome, Italy) presented an extensive review of equine arteritis virus infection in Italian stallions,
confirming the existence of both short- and long-term carriers of the virus in different breeds of horses and also in
donkeys. The carrier rate among seropositive stallions varied from 10% to 37.5%, the latter being recorded in
jackasses. The rate among stallions of Arabian, Standardbred, and Thoroughbred breeds was 31.2%, 31.5% and
20%, respectively. Regular sampling of five carrier stallions over a 9-month period failed to provide any evidence of
intermittency of virus shedding in the semen of any of these animals. Spontaneous clearance of the virus was
demonstrated in two long-term carrier stallions. Experimental studies with semen from a carrier stallion of Italian
origin confirmed the pathogenicity of this strain of equine arteritis virus. Characteristic signs of EVA developed in
22
Standards Commission/September 96
both inoculated and in-contact horses with some animals becoming severely ill. Clinical, virological and serological
responses were described and the shedding patterns of equine arteritis virus in respiratory secretions, semen and
urine and in leukocytes and serum were defined. It is noteworthy that urine remained infectious after being stored for
7 days at an ambient temperature ranging from 24Erreur ! Source du renvoi introuvable.C to 30Erreur ! Source
du renvoi introuvable.C. This is longer than has previously been reported and may be of significance in the
transmission and epidemiology of this infection.
The final paper of the morning session of the symposium was given by Dr O.-R. Kaaden (Munich, Germany) and
dealt with the epidemiology of equine arteritis virus in Germany. Based on an extensive serological survey initiated
in 1987, the seroprevalence of antibodies to equine arteritis virus increased very significantly from 1.8% in 1987/88
to 24.8% in 1994. Additionally, isolations of the virus were made from semen, unclotted blood and from tissues
from a number of cases of equine abortion. Attempted virus isolation in cell culture was found to be superior to the
PCR assay for the detection of equine arteritis virus in diagnostic material. It was felt that additional work needed to
be done on standardisation of the PCR assay. EVA has been considered to be eradicated in Germany for decades. In
recent years, mild cases of the disease have been reported and carrier stallions were considered to be primarily
responsible for the spread of the infection. In light of the changing disease situation, EVA was declared a seminotifiable disease in Germany in March 1995. A voluntary programme of eradication was proposed which would
entail initial serological screening of all stallions prior to the start of the breeding season, with follow-up
identification of any seropositive carrier stallions. All shedding stallions would be quarantined and restrictions
placed on the importation of carrier stallions or virus infective semen into the country.
The afternoon session of the symposium, which was chaired by Dr M. Horzinek (Utrecht, The Netherlands),
provided the opportunity for national representatives from different countries to review the EVA status of their
respective country. Dr S. Kölbl (Vienna, Austria) reported on the laboratory diagnosis of EVA in Austria where the
disease is notifiable. Some 27.3% of 967 sera examined between 1992 and 1996 were serologically positive to
equine arteritis virus. Most of the infections were subclinical. The virus was a far less significant cause of abortion
than equine herpesvirus 1, being identified in 3.8% of 131 equine abortions. In the past 2 years, the carrier state has
been confirmed in a limited number of stallions.
The prevalence of equine arteritis virus infection in France, where EVA is still a non-notifiable disease, was
commented on by Dr E. Plateau (Paris, France). The prevalence of equine arteritis virus infection in sera submitted
for routine testing varies between 1% and 3%, and only occasional outbreaks of EVA have been confirmed over the
past 10 years. The French National Stud regulates all breeding stallions in France, and any stallions seropositive for
antibodies to equine arteritis virus are screened by virus isolation and PCR assay for the carrier state.
EVA is a reportable but non-notifiable disease in Germany according to Dr H. Bätsa (Bonn, Germany). Measures to
control the introduction of equine arteritis virus into the country by way of carrier stallions or infective semen were
in accordance with those formulated by the EU. Similar controls were in place at centres used to collect semen for
artificial insemination purposes. The feasibility of requiring seronegative stallions to be vaccinated against EVA is
under current consideration.
Dr H. Gunn (Dublin, Ireland) reported that EVA had never been confirmed in Ireland, in which country the disease
is currently notifiable. The seroprevalence of equine arteritis virus infection among Thoroughbreds in a survey
conducted in 1991 was only 0.3%. In 1996, Ireland enacted the EVA Order aimed at controlling stallions and their
semen that are infected or suspected to be infected with equine arteritis virus. The use and movement of mares that
are suspected of having been recently infected with the virus is similarly controlled. Measures to prevent the
introduction of the virus or to deal with an outbreak of EVA should it occur, are provided in the Voluntary Code of
Practice which is widely observed by the country’s Thoroughbred industry. Vaccination of stallions with an
inactivated vaccine against EVA is permitted under special license.
Further to his earlier paper on the EVA situation in Italy, Dr G. Autorino (Rome, Italy) reported that a national plan
for the control of EVA had been introduced in January 1994. Under the provisions of this programme, virus
shedding stallions can still continue to be used for commercial breeding purposes, but only with special ministerial
authorisation. Where authorisation is granted, such stallions can only be used for natural breeding and not for
artificial insemination. Conditions have been formulated for accrediting breeding farms to be free of EVA.
Dr B. Colenbrander (Utrecht, The Netherlands) in commenting on the EVA situation in The Netherlands,
confirmed that the disease was not currently regulated in that country. Occasional outbreaks had been reported
primarily in riding horses. A significant percentage of horses screened by the rGL ELISA have been found to be
seropositive for antibodies to equine arteritis virus, with the percentage as high as 45% in horses over 4 years of age.
Very little difference in seroprevalence was noted between Warmblood (approximately 35%) and Standardbred
(approximately 33%) horses. Eradication of EVA is not considered to be a realistic proposition at this time.
Dr A. Albihn (Uppsala, Sweden) reported that Sweden had very few outbreaks of EVA over the years in spite of
significant serological evidence of the infection among Swedish Warmblood and Standardbred horses. Compulsory
Standards Commission/September 96
23
screening of all stallions used for artificial insemination for evidence of the carrier state was introduced in 1992. The
shedding status of carrier stallions was confirmed by virus isolation in cell culture or by the nested PCR assay.
Shedding stallions can continue to be used for breeding, but mare owners must be notified of a stallion’s carrier
status. Seroprevalence of equine arteritis virus infection in Standardbreds and Swedish Warmbloods have been
found to be 35% and 16%, respectively. The carrier rate among seropositive stallions was 32% in Standardbreds and
21% in Warmbloods. No differences in pregnancy rates have been recorded in mares bred to virus-shedding versus
non-shedding stallions. The measures enacted to control the spread of equine arteritis virus infection in Sweden have
been supported by the horse industry which does not recognise EVA as a disease warranting a more restrictive
national control programme.
Successive serological surveys carried out in Switzerland between 1988 and 1994 indicated a low prevalence of
equine arteritis virus infection (4-5%) countrywide according to Dr M. Weiss (Bern, Switzerland). The lowest rate
of infection was in non-breeding categories of horses. No clinical evidence of EVA had been reported since 1975. In
spring 1995, however, a series of outbreaks of EVA occurred which lasted about 3 months and which probably
originated from a dealer’s yard. Clinical disease of varying severity was observed. Although 20% of 648 horses at 11
stables seroconverted, the virus did not appear to be highly contagious. This contrasts with venereal transmission of
equine arteritis virus by carrier stallions which was found to be highly efficient. The virus neutralisation test, virus
isolation in cell culture and the PCR assay comprise the tests in routine use in Switzerland for diagnosis of equine
arteritis virus infection. No specific control measures were taken as a consequence of the 1995 series of EVA
outbreaks. With the exception of breeding stallions, there are no specific requirements on horses imported into
Switzerland from countries in the EU.
In concluding the status reports on EVA in those European countries represented at this symposium, Mr T. Davies
(Tolworth, UK) reviewed the situation in the UK, both before and after the first recorded outbreak in that country in
1993. The seroprevalence of infection, which was 0.5% prior to 1993, has since increased to 2-3%. EVA is a
notifiable disease in the UK and post-importation testing is required on all stallions from approved third countries.
Any carrier stallions detected in the country must be reported to the ministerial authorities. The identification of such
animals is publicised, but carrier stallions can be used for commercial breeding purposes provided certain strict
requirements are met. EVA continues to be regarded as a significant disease in the UK and appropriate measures
have been taken to safeguard the country’s current disease-free status.
Mr T. Davies (Tolworth, UK) representing Dr B. van Gothem (European Union) presented an overview of the
Community legislation on EVA in relation to the trade and importation of equidae. This included the directives
governing trade between member states within the Community as well as between member countries and approved
third countries.
The symposium finished with a lively and far-reaching discussion on different aspects of EVA. The procedures used
in the diagnosis of this infection were a subject of much detailed discussion. Difficulties have been encountered by
certain laboratories in isolating equine arteritis virus, especially from stallion semen. Aside from appropriate
pretreatment of samples, the single most important factor influencing the outcome of attempted virus isolation in cell
culture is the cell system used. The RK-13 cell line (rabbit kidney) appears to provide the greatest sensitivity for the
primary isolation of equine arteritis virus from a variety of sources, especially from semen. The need for further
validation of alternative techniques for the detection of virus or viral products was emphasised, as was the need for
greater standardisation of the virus neutralisation and ELISA tests for the serological diagnosis of this infection. The
current chapter on EVA in the OIE Manual of Standards for Diagnostic Tests & Vaccines needs to be updated to
provide more detailed information on screening semen for equine arteritis virus and on alternative, newer
technologies, such as the PCR assay for the detection of this infection. Considerable discussion ensued on how best
to control EVA both at a national level and within the Community. Various viewpoints were presented on how this
could be achieved, with opinions differing on whether control as opposed to eradication of this infection was the
more logical, practicable and realistic approach to take. It was felt by many that measures formulated to control EVA
should not be disproportionate in relation to the veterinary medical significance of this infection. EVA is perceived
by some as a disease of acquired political significance since the epidemic in Thoroughbred breeding farms in
Kentucky in 1984. EVA continues to impact significantly on the international movement of horses and,
through the offices of OIE, every effort should be made to seek greater harmonisation of the import health
requirements of countries for this disease.
24
Standards Commission/September 96