Download OIE requirements to equine vaccines and laboratory tests: review on

OIE requirements to equine vaccines and laboratory tests:
review on the commercial tests and vaccines in use worldwide
E.F.Zabegina
The All-Russian Institute of Experimental Veterinary Medicine &
Moscow, Russia
Email: [email protected]
Equicentre EZ Ltd.,
Introduction
The horse population on the globe is not so big in comparison to the other domestic
animals. However, the industry of horse-breeding is one of the major agricultural branches
worldwide. Currently the main attention is given to the breeding of especially valuable
breeds of horses, and in such situation the most important points are diagnosis and
prophylaxis of infectious diseases as they can cause considerable economical injury and
influence selection activity. Besides, correct diagnosis and prophylaxis of equine infectious
diseases are extremely important for international movement of horses. This movement
involves all types of countries and breeds. Nowadays, even countries with a “low” sanitary
status can export very valuable specimens of equidae.
A common point in all the controls of international movements of animals is the veterinary
certification, standardisation and harmonization of the laboratory tests. Initially, The
Standard Manual of the OIE is the recognized guide for technical procedures to which all
the veterinary laboratories and manufacturers of the veterinary vaccines must refer. The
necessity of international perfecting and harmonization of diagnostic methods and means of
specific prophylaxis of the most widespread equine diseases is of great importance.
The main line of OIE in connection to all the OIE laboratory tests and all the approved by
OIE vaccines is: 1) all the internationally prescribed tests should be standardised, 2) all the
vaccines should be effective, safe and contain epizootically actual strains.
Brief review on major transmissible horse diseases
Diseases notifiable to the OIE used to be classified into two lists: List A and List B. In May
2004, OIE Members approved the creation of a single list of diseases notifiable to the OIE.
Modifications to the List can be made annually, subject to the approval of the International
Committee during its General Session. The modified List does not come into force until the
following January, so as to ensure that the list of diseases remains the same for any given
calendar year. Proposed changes to the List are based on a decision tree contained in an
OIE international standard. A new list has been approved in May 2008 by the International
Committee and came into force in 2009.
OIE Equine Listed Diseases:
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African horse sicknesness
Contagious equine metritis
Dourine
Equine encephalomyelitis (Eastern)
Equine encephalomyelitis (Western)
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Equine infectious anaemia
Equine influenza
Equine piroplasmosis
Equine rhinopneumonitis
Equine viral arteritis
Glanders
Surra (Trypanosoma evansi)
Venezuelan equine encephalomyelitis
Vesicular stomatitis
African horse sickness (AHS)
Previously List A
AHS can cause a high mortality in horses, especially when cases occur in areas where the
disease is not currently present and where the horses do not have natural resistance.
Mules, donkeys, zebra are unapparently infected and can be source of infection. The
presence of culicoides is of major importance.
Prescribed tests:
• CFT (local preparation of reagents)
• Indirect ELISA Test: new and more sensitive test (VP7 protein antigen)
• NS3 ELISA Test: Differentiation of vaccinated from non-vaccinated horses.
Alternative Tests:
• Agent identification (real-time PCR)
• VN
Vaccines are available.
Vesicular stomatitis (VS)
Previously List A
VS can be transmitted to humans and is indistinguishable from foot and mouth disease in
ruminants and pigs or swine vesicular disease in pigs. This is the main reason of its
importance. Disease is spread only in the Americas.
Prescribed tests:
Tests are very strictly performed in the laboratories specialized on vesicular diseases
(FMD., SVD, VS)
• ELISA Test: the test can be a direct or a competition test. Interesting because of the
use of inactivated antigen.
• VN: actual in cases when horse sera have to be tested in small number and from
time to time (sporadically)
• CFT: less interesting with sera of equidae due to possible anticomplementarity
Alternative Tests:
• Not approved by OIE
Vaccines are available.
Equine infectious anaemia (EIA)
Previously List B
EIA is characterised with a fatal chronic evolution. No medical prophylaxis, no therapy. Sub
clinically infected animals can introduce the disease (long-life carriers). EIA is presented in
many horse populations, but very specific and reliable detection test is developed.
Prescribed test:
• Agar Gel Immunodiffusion Test (Coggins test): the Golden Standard of EIA
diagnosis. Reagents are commercially available, simple equipment and facilities are
used.
Alternative Test:
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ELISA Test: gives a quick response but not wildly accepted. Positive tests must be
reconfirmed by AGID test
No vaccines available.
Equine influenza
Previously List B
Disease is highly contagious and can cause high morbidity but low mortality. Risk is very
much reduced by vaccination but epidemics are regularly observed in non-immune
populations.
Prescribed test:
• Not available
Alternative Test:
• HI
Vaccines are available and widely used.
Equine viral arteritis (EVA)
Previously List B
EVA moderates clinical signs, abortions. Risk is important for non-immune populations (the
reason are shedder stallions).
Prescribed tests:
• Agent identification (in semen only)
• VN: a conventional seroneutralisation test, but sensitivity highly affected by the viral
strain and its passage history.
Alternative Test:
• Not approved by OIE
Vaccines are available.
There are debates around vaccination (alive and inactivated vaccines).
Equine rhinopneumonitis
Previously List B
It causes respiratory signs, abortions, nervous disorders (few mortalities). Risk: non-immune
populations (young and unvaccinated animals, pregnant mares, closed populations)
Prescribed test:
• Not approved by OIE
Alternative Test:
• VN
Some countries use IHAT.
Vaccines are available and widely used.
Equine encephalomyelitis: Eastern and Western
Previously List B
Risk of the disease prevails in the Americas.
Prescribed test:
• Not approved by OIE
Alternative Tests:
• CFT
• HI
• Plaque Reduction Test
Alternative tests are used for diagnosis or control of immunity (especially if vaccination is
compulsory).
Vaccines are available.
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Venezuelan equine encephalomyelitis
Previously List B
Risk of the disease prevails in the Americas.
Prescribed test:
• Not approved by OIE
Alternative Tests:
• CFT
• HI
• PRN
Vaccines are available.
Contagious equine metritis
Previously List B
CEM causes temporary infertility. Disease is correlated to the concerned breeds
(International Code of Practice for Thoroughbreds) and consequences on the sanitary
status of the exporting country.
Prescribed test:
• Agent identification. Isolation of the germ. Conventional bacteriology, but requesting
good experience in isolation and characterisation of T. equigenitalis (accredited
laboratories).
Alternative Test:
• Not approved by OIE
No vaccines available.
Dourine
Previously List B
Dourine is very dangerous because of significant morbidity and mortality. Risk: carrier
status.
Prescribed test:
• CFT (reagents are locally produced or commercially available)
Alternative Test:
• Not approved by OIE
However, some laboratories use Immunofluorescent Test and Direct ELISA Test. Crossreactions with Surra (T. Evansi) can be observed.
No vaccines available.
Surra (Trypanosoma evansi)
Previously List B
Cross-reactions with Dourine (T. Equiperdum) can be observed.
Prescribed test:
• Not approved by OIE
Alternative Test:
• Not approved by OIE
However, PCR is in development.
No vaccines available.
Equine piroplasmosis
Previously List B
Sub acute or chronic infection. Acute and fatal cases can be notified. All the seropositive
animals must be considered as inapparent carriers. Presence of vectors is essential.
Prescribed tests:
• ELISA
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• IFA
Alternative Test:
• CFT: compulsory requested for export of horses to some countries: USA, Japan,
Russia, etc. Antibodies can vary along the life of an infested animal even after
specific therapy.
However, Indirect Immunofluorescence Test is an alternative test accepted by some
countries. ELISA Tests are in development.
No vaccines available.
Glanders
Previously List B
Glanders is a highly contagious disease. Problem: sub clinically infected animals,
contagious for humans (lethal). The exact status of this disease is unknown in many
regions. Risk: importation of horses from countries with unknown sanitary status.
Prescribed tests:
• CFT: reagents are locally produced or commercially available
• Mallein Test
Alternative Test:
• Not approved by OIE
However, ELISA is developed in some countries.
No vaccines available.
Leptospirosis
Not on the OIE List
However, sometimes is requested to be tested for international trade or movement.
Zoonosis, and can cause various clinical signs in animals species including uveitis and
abortions in horses. Prevalent in all the hemispheres. Risk: introduction of new serovars in
importing countries
Laboratory Test:
• Micro Agglutination Test. Requests fresh antigens and examination against multiple
serovars; levels of positivity are not standardized.
Vaccines are available.
Discussion
A specific point for sanitary control concerning population of equidae is the reduced number
of laboratories able to realize the different prescribed tests for international trade. In most
cases samples are sent to the National Reference Laboratories. On the other hand,
Reference Laboratories are more involved in research, development and expertise than
routine analysis. If to talk about the strategy of vaccination, it is based on the danger and
risk caused by the disease as well as by sanitary status of the country. In this connection
the role of OIE is invaluable as an institution which collects and spreads the information so
that to assist in validation, standardization and harmonization of the laboratory tests for
international trade and movement of horses as well as runs the monitoring on all the OIE
Listed diseases worldwide with the purpose to select epizootically actual strains to be used
for manufacturing of vaccines.
Conclusion
Equine transmissible diseases which can cause considerable economical injury and
influence selection activity should be traced by the routine internationally standardized
laboratory tests and prevented by specific prophylaxis with using epizootically actual
vaccines.
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Referenses
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infections. - Infectious Diseases of Livestock, Coetzer J.A.W., Thomson G.R. &
Tustin R.C., 2004, eds. Oxford University Press, Cape Town, South Africa.
2. Horserace Betting Levy Board. Code of Practice on Contagious Equine Metritis,
Equine Viral Arteritis, Equine Herpesvirus and Guidelines on Strangles. – 2005,
London, UK, www.hbld.org.uk
3. Claes F., Ilgekbaeva G., Verloo D., Saidouldin T., Geerts S., Buscher P., Goddeeris
B. Comparison of serological tests for equine trypanosomosis in naturally infected
horses in Kazakhstan. – Vet.Parasitol., 2005, 131 (3-4), 221-225
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view of the laboratory. – Proc. 3rd International Conference “Equine Diseases:
Diagnosis, Prophylaxis, Treatment”, 2003, Moscow, pp.6-9
5. Terrestrian Animal Health Code. - Manual of Diagnostic Tests and Vaccines for
Terrestrial Animals. 2008, Paris, www.oie.int
6. Westcott D. The isolation of equine arteritis virus (EAV) from equine semen. – CVL
Weybridge Vir. Meth., 1997, D76, pp. 1-7
7. Yurov •.P., Zablotskiy V.T., Zabegina E.F. Harmonisation of methods for equine
infectious and invasive diseases diagnosis at the OIE reference laboratories in
Russia. - Proc. 10th WEVA Congress, 2008, Moscow, Russia, pp. 426-427
8. Yurov K.P. Equine viral arteritis. – Referent Veterinary Journal, Kolos, 2006, No.3,
p.27
9. Zablotsky V.T., Georgiu Ch., Kazakov N.A., Mutuzkina Z.P. Method
recommendations on laboratory diagnosis of piroplasmidosis of animals. - New
methods of testing in veterinary medicine, Part. IV, Moscow, 2008, pp. 256-262
10. Zablotsky V.T., Georgiu Ch. Methodological recommendations on diagnosis of
dourine using antigens T.equiperdum in ELISA. – New Research Methods in
Veterinary Medicine, 2006, part 2, Moscow, pp.163-172
11. Zabegina E.F. Diagnosis of equine respiratory viral diseases. – Proc. Res.Pract.Conf. “Equine diseases”, Novosibirsk, 2006, pp.20-26
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Moscow, No.1, 2006, pp.10-11
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