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THE COMMISSION OF THE EUROPEAN COMMUNITIES,
Having regard to the Treaty establishing the European Community,
Having regard to Council Directive 2001/89/EC of 23 October 2001 on Community measures for the control of classical swine fever(1), and in particular Article 17(3) and Article 29(1) thereof,
Whereas:
(1)
It is necessary to lay down at Community level diagnostic procedures, sampling methods and criteria for the evaluation of the results of laboratory tests for the confirmation of classical swine fever.
(2)
Annex IV to Directive 2001/89/EC lays down the functions and duties of the Community Reference Laboratory for classical swine fever in order to coordinate, in consultation with the Commission, the methods employed in the Member States for diagnosing the disease; these functions and duties include the organisation of periodic comparative tests and the supplying of standard reagents at Community level.
(3)
Classical swine fever virus is not considered to be a hazard for human health.
(4)
Laboratory tests have been recently developed to ensure a quick diagnosis of classical swine fever.
(5)
The experience gained in the control of classical swine fever in recent years has resulted in the identification of the most suitable sampling procedures and criteria for evaluation of the results of the laboratory tests for a proper diagnosis of this disease in different situations.
(6)
The measures provided for in this Decision are in accordance with the opinion of the Standing Veterinary Committee,
HAS ADOPTED THIS DECISION:
1.Member States shall ensure that the confirmation of classical swine fever is based on:
(a)the detection of clinical signs and post-mortem lesions of disease;
(b)the detection of virus, antigen or genome in samples of pig tissues, organs, blood or excreta;
(c)the demonstration of a specific antibody response in blood samples,
in accordance with the procedures, sampling methods and criteria for evaluation of the results of laboratory tests laid down in the Manual annexed to this Decision.
2.However, the national diagnostic laboratories referred to in Annex III(1) to Directive 2001/89/EC may apply modifications to the laboratory tests referred to in the Manual annexed to this Decision, or use different tests, provided that an equal sensitivity and specificity can be demonstrated.
The sensitivity and specificity of these modified or different tests must be evaluated in the framework of the periodic comparative tests organised by the Community Reference Laboratory for classical swine fever.
Annexes I and IV to Council Directive 80/217/EEC of 22 January 1980 introducing Community measures for the control of classical swine fever(2), as last amended by the Act of Accession of Austria, Finland and Sweden, are hereby repealed.
This Decision shall apply from 1 November 2002.
This Decision is addressed to the Member States.
Done at Brussels, 1 February 2002.
For the Commission
David Byrne
Member of the Commission
The typical haemorrhages of the skin, are usually observed on the ear, tail, abdomen and the inner side of the limbs during the second and third week after infection until death. Neurological signs are frequently seen, such as a staggering hind limb gait, in coordination of movement, and convulsions.
A constant finding is fever. This is usually higher than 40 °C, but in adult pigs fever may not exceed 39,5 °C.
Death occurs usually within one month. Recovery with production of antibodies does occur, most often in adult breeding animals which do not display severe clinical signs. Antibodies against classical swine fever virus are detectable from 2 to 3 weeks post infection onwards.
Acute classical swine fever must also be considered in case of suspected erysipelas, porcine reproductive and respiratory syndrome, coumarin poisoning, purpura haemorragica, post-weaning multisystemic wasting syndrome, porcine dermatitis and nephropathy syndrome, salmonella or Pasteurella infections or any enteric or respiratory syndromes with fever which do not respond to antibiotic treatment.
These pigs may show clinical signs of disease for 2 to 3 months before death. Classical swine fever virus is constantly shed from the onset of clinical signs until death. Antibodies may be temporarily detected in serum samples.
The outcome of trans-placental infection of foetuses depends largely on the stage of gestation and viral virulence. Infection during early pregnancy may result in abortions and stillbirths, mummification and malformations. All this leads to a reduction of the fertility index in the holding.
Infection of sows at up to 90 days of pregnancy can lead to the birth of persistently viraemic piglets, which may be clinically normal at birth and survive for several months. After birth, they may show poor growth, wasting or occasionally congenital tremor. This course of infection is referred to as "late onset classical swine fever". These piglets may play a crucial role in spreading the disease and in the maintenance of virus persistence within a population, as they constantly shed virus until death.
In case of suspicion of an infectious disease of the reproductive tract, investigation for classical swine fever must be immediately carried out whenever the holding in question can be considered at risk (e.g. due to location of the holding in an area where classical swine fever occurs in feral pigs), and in any case as soon as more common infectious diseases of the reproductive tract have been excluded.
The decision to recognise a holding as a suspected holding will be taken on the basis of the following findings, criteria and grounds:
clinical and pathological findings in pigs. The main clinical and pathological findings to be considered are:
fever with increased morbidity and mortality;
fever with haemorrhagic syndrome;
fever with neurological symptoms;
fever of unknown origin where treatment with antibiotics failed to improve the health state;
abortions and increased fertility problems during the last three months;
congenital tremor of piglets;
chronically diseased animals;
growth retarded (runted) young animals;
petechial and ecchymotic haemorrhages, especially in lymph nodes, kidneys, spleen, bladder and larynx;
infarction or haematomas, notably in the spleen;
button ulcers in the large intestine of chronic cases, particularly near the ileo-caecal junction.
epidemiological findings. The main epidemiological findings to be considered are:
where pigs had direct or indirect contact to a pig holding proven to have been infected with classical swine fever;
where a holding has supplied pigs that were subsequently shown to be infected with classical swine fever;
where sows have been artificially inseminated with semen originating from a suspect source;
where there has been indirect or direct contact with feral pigs of a population where classical swine fever occurs;
where pigs are kept outdoors in a region where feral pigs are infected with classical swine fever;
where pigs have been fed with swill and there is the suspicion that this swill has not been treated in such a way as to inactivate classical swine fever virus;
where possible exposure might have occurred, e.g. due to persons entering the holding, transports, etc.
findings related to results of serological tests. The main laboratory findings to be considered are:
Irrespective of the adoption of the measures referred to in Article 4(2) of Directive 2001/89/EC in the holding in question, those guidelines and procedures shall also apply in cases of disease whenever classical swine fever is considered in the differential diagnosis. This will include occasions when the clinical signs and epidemiological pattern of disease that are observed in pigs suggest a very low probability of occurrence of classical swine fever.
In all other cases where one or more pigs are suspected of being infected with classical swine fever virus, the measures referred to in Article 4(2) of Directive 2001/89/EC shall be adopted in the suspected holding in question.
In case of suspicion of classical swine fever in pigs in a slaughterhouse or means of transport, the guidelines and procedures laid down in subparagraphs 2 to 7 shall also apply mutatis mutandis.
The clinical examination must include the taking of body temperature and must primarily concern the following pigs or group of pigs:
sick or anorexic pigs;
pigs recently recovered from disease;
pigs recently introduced from confirmed outbreaks or from other suspected sources;
pigs kept in sub-units recently visited by external visitors which had a recent close contact with classical swine fever suspected or infected pigs or for which other particularly risky contacts with a potential source of classical swine fever virus have been identified;
pigs already sampled and serologically tested for classical swine fever, in case the results of these tests do not allow to rule out classical swine fever, and in-contact pigs.
If the inspection in the suspected holding has not indicated the presence of the pigs or group of pigs referred to in the above subparagraph, the competent authority, without prejudice to other measures that may be applied in the holding in question in accordance with Directive 2001/89/EC and taking into account the epidemiological situation, shall:
carry out further examinations in the holding in question in accordance with subparagraph 3 below; or
ensure that blood samples for laboratory tests are taken from the pigs in the holding in question. In this case the sampling procedures laid down in subparagraph 5 and in F.2, shall be used for guidance purposes; or
adopt or maintain the measures laid down in Article 4(2) of Directive 2001/89/EC, pending further investigations in the holding in question; or
rule out the suspicion of classical swine fever.
The minimum number of pigs to be examined must allow for the detection of fever if it occurs at a prevalence of 10 % with 95 % confidence in these sub-units.
However, in case of:
breeding sows, the minimum number of sows to be examined must allow for the detection of fever if it occurs at a prevalence of 5 % with 95 % confidence;
at semen collection centres, all boars must be examined.
If these examinations have not shown lesions suggesting classical swine fever but, due to the epidemiological situation, further investigations are deemed necessary:
a clinical examination, as laid down in subparagraph 3, and blood sampling as laid down in subparagraph 5 must be carried out in the sub-unit where the dead or moribund pigs were kept; and
post-mortem examinations may be carried on 3 to 4 in-contact pigs.
Irrespective of the presence or absence of lesions suggesting classical swine fever, samples of the organs or tissues from pigs that have been subjected to post-mortem examination must be collected for virological tests in accordance with Chapter V B. 1 These samples must be preferably collected from recently dead pigs.
When post-mortem examinations are carried out the competent authority must ensure that:
the necessary precautions and hygienic measures are taken to prevent any disease spread; and,
in case of moribund pigs, they are killed in a humane way in accordance with Council Directive 93/119/EEC.
The minimum number of samples to be taken for serological tests must allow for the detection of 10 % seroprevalence with 95 % confidence in the sub-unit in question.
However, in the case of:
breeding sows, the minimum number of sows to be sampled must allow for the detection of 5 % seroprevalence with 95 % confidence(8);
a semen collection centre, blood samples must be taken from all boars.
The number of samples to be taken for virological tests will be in accordance with the instructions of the competent authority, which will take into account the range of tests that can be performed, the sensitivity of the laboratory tests that will be used and the epidemiological situation.
Samples for virological tests may also be taken in accordance with the instructions of the competent authority, which will take into account the range of tests that can be performed, the sensitivity of the laboratory tests that will be used and the epidemiological situation.
pigs showing signs or post-mortem lesions suggesting classical swine fever and their in-contact pigs;
other pigs which might have had risky contacts with infected or suspected pigs or which are suspected to have been contaminated with classical swine fever virus.
These pigs must be sampled in accordance with the instructions of the competent authority, which will take into account the epidemiological situation. In this case, the sampling procedures laid down in the second, third and fourth subparagraphs below shall be used for guidance purposes.
Furthermore, pigs proceeding from each of the sub-units of the holding must be sampled at random(10). In this case, the minimum number of samples to be taken for serological tests must allow for the detection of 10 % seroprevalence with 95 % confidence in the sub-unit in question.
However, in the case of:
breeding sows, the minimum number of sows to be sampled must allow for the detection of 5 % seroprevalence with 95 % confidence(11);
a semen collection centre, blood samples must be taken from all boars.
The type of samples to be taken for virological tests and the test to be used will be in accordance with the instructions of the competent authority, which will take into account the range of tests that can be performed, the sensitivity of these tests and the epidemiological situation.
The minimum number of pigs to be checked must allow for the detection of fever if it occurs at a prevalence of 10 % with 95 % confidence in these sub-units.
However, in the case of:
breeding sows, the minimum number of sows to be examined must allow for the detection of fever if it occurs at a prevalence of 5 % with 95 % confidence in the sub-unit where the sows to be moved are kept;
boars, all boars to be moved must be examined.
The minimum number of the pigs to be checked must allow for the detection of fever if it occurs at a prevalence of 20 % with 95 % confidence in the sub-units in question.
However, in the case of breeding sows or boars, the minimum number of pigs to be examined must allow for the detection of fever if it occurs at a prevalence of 5 % with 95 % confidence in the subunit where the pigs to be moved are kept.
The minimum number of samples to be taken must allow for the detection of 10 % seroprevalence or virus prevalence with 95 % confidence in each sub-unit.
However, in the case of breeding sows or boars the minimum number of pigs to be sampled must allow for the detection of 5 % of seroprevalence or virus prevalence with 95 % confidence in the subunit where these pigs were kept.
The type of samples to be taken and the test to be used will be in accordance with the instructions of the competent authority, which will take into account the range of tests that can be performed, the sensitivity of these tests and the epidemiological situation.
in case sentinel pigs are reintroduced, blood samples for serological tests must be taken at random from a number of pigs that allow for the detection of 10 % seroprevalence with 95 % confidence in each sub-unit of the holding;
in case of total re-population, blood samples for serological tests must be taken at random from a number of pigs that allow for the detection of 20 % seroprevalence with 95 % confidence in each sub-unit of the holding.
However, in the case of breeding sows or boars the number of samples to be taken must be such as to detect 10 % seroprevalence with 95 % confidence.
a clinical examination must be carried out in accordance with the procedures laid down in A.2 and 3;
blood samples for serological tests must be taken as laid down in subparagraph 2.
However, in the case of:
breeding sows, the minimum number of samples to be taken must allow for the detection of 5 % seroprevalence with 95 % confidence;
a semen collection centre, blood samples must be taken from all boars.
In addition, blood samples for serological tests must be taken from pigs:
in all the holdings where no pigs of between two and eight months of age are kept;
whenever the competent authority deems that classical swine fever might have spread unnoticed amongst breeding sows;
in any other holding where sampling is deemed necessary by the competent authority;
in all semen collection centres.
It is also recommended that:
in areas where hunting pressure is higher and regularly performed, or selective hunting is carried out as a disease control measure, approximately 50 % of the sampled animals belong to the three months to one year age class, 35 % to one to two years age class and 15 % to more than 2 years age class;
in areas where hunting pressure is very low or absent, at least 32 animals are sampled for each one of the three age classes;
sampling is performed in a short time, preferably not more than one month;
the age of sampled animals is identified according to the teeth eruption.
When virological monitoring on shot feral pigs is deemed necessary, it must be primarily carried out on animals three months to one year old.
In the case of pigs kept in holdings, clear information on age, category and holding of origin of the pigs sampled must be provided. It is recommended that the location of each pig sampled in the holding be recorded together with its unique identification mark.
The principle of the test is the detection of viral antigen on thin cryosections of organ material from pigs suspected of being infected with classical swine fever virus. The intracellular antigen is detected by using a FITC conjugated antibody. A positive result should be confirmed by repeating the staining with a specific monoclonal antibody.
Suitable organs are tonsils, kidney, spleen, different lymph nodes and ileum. A smear of bone marrow cells might also be used in case of feral pigs, if these organs are not available or are autolysed.
The test can be performed within one day. As organ samples can only be obtained from dead animals its use for screening purposes is limited. Confidence in the test result may be limited by doubtful staining, particularly where considerable experience in performing the test has not been acquired or if the organs tested are autolysed.
Viral antigen is detected by using various ELISA techniques. The sensitivity of the antigen ELISA should be high enough to score a positive result from animals showing clinical signs of classical swine fever.
The use of ELISA for antigen detection is recommended on samples from animals with clinical signs or pathological lesions of disease. It is not suitable for the investigation of individual animals. Suitable samples are leukocytes, serum, non-coagulated blood as well as suspensions of the organs referred to in subparagraph 1 taken from pigs suspected of being infected with classical swine fever virus(13).
The ELISA can be carried out within one day and can be performed by automatic equipment. The most important advantage is that large numbers of samples can be processed in a short period of time. It is recommended that ELISA antigen which give satisfactory results on reference material are used. However, at present all commercial ELISA are less sensitive than the virus isolation on cell culture and their sensitivity is significantly better on blood samples from piglets than from adult pigs.
Classical swine fever virus isolates obtained in this way are useful for virus characterisation including genetic typing and molecular epidemiology.
In any case, these virus isolates must be sent to the Community Reference Laboratory for virus collection without delay.
Virus isolation must be considered as the reference virological test and must be used as confirmatory test when necessary. Its use is particularly recommended in case positive FAT, ELISA or PCR results are not associated with the detection of clinical signs or lesions of disease and in any other doubtful case.
However, a primary outbreak of classical swine fever can be confirmed if clinical signs or lesions of disease have been detected in the pigs in question and at least two antigen or genome detection tests have given a positive result.
A secondary outbreak of classical swine fever can be confirmed if, in addition to the epidemiological link to a confirmed outbreak or case, clinical signs or lesions of disease have been detected in the pigs in question and an antigen or genome detection tests has given a positive result.
A primary case of classical swine fever in feral pigs can be confirmed after virus isolation or if at least two antigen or genome detection tests have given a positive result. Further cases of classical swine fever in feral pigs for which an epidemiologial link with previously confirmed cases have been found can be confirmed if an antigen or genome detection test has given a positive result.
Genetic typing of classical swine fever virus isolates is of major importance to determine the source of disease. However, a close relationship between viruses obtained from different outbreaks is not an absolute proof for a direct epidemiological link.
The data on typing and sequencing of classical swine fever virus isolates available to the laboratories authorised to diagnose classical swine fever must be forwarded to the Community Reference Laboratory in order that this information is entered into the database kept by this laboratory.
The information included in this database must be available to all national reference laboratories in the Member States. However, for the purpose of publication on scientific journals, if requested by the laboratory in question, the Community Reference Laboratory shall guarantee confidentiality of these data until they are published.
Pigs infected in utero may be immunotolerant against the homologue classical swine fever virus and produce no specific antibodies. However, antibodies of maternal origin can be detected during the first days of life. The half-life of maternal antibodies in non-viraemic healthy piglets is about two weeks. If found in piglets older than three months, classical swine fever antibodies are very unlikely to be of maternal origin.
A few seropositive pigs with a low neutralisation titre can be indicative of a recent infection (two to four weeks). Many pigs with high neutralisation titre could indicate that virus entered the holding more than one month before. The location of seropositive pigs in the holding can provide valuable information on how classical swine fever virus entered the holding.
However, an accurate evaluation of the results of the serological tests must be carried out taking into account the whole clinical, virological and epidemiological findings, in the framework of the enquiry to be carried out in case of suspicion or confirmation of classical swine fever, in accordance with Article 8 of Directive 2001/89/EC.
The quality and efficiency of the serological diagnosis performed by the national laboratories must be regularly checked in the framework of the inter-laboratory comparison test periodically organised by the Community Reference Laboratory.
A constant amount of classical swine fever virus is incubated at 37 °C with diluted serum. For screening purposes, the sera are initially diluted 1/10. When a full titration is necessary two-fold dilutions of serum starting at 1/2 or 1/5 can be prepared. Each dilution is mixed with an equal volume of a virus suspension containing 100 infectious doses (TCID 50).
After incubation the mixture is inoculated onto cell cultures which are incubated for three to five days. After this incubation period the cultures are fixed and any viral replication in the infected cells is detected by an immune labelling system. Either the neutralisation peroxidase-linked antibody (NPLA) or the neutralisation-immunofluorescence (NIF) assays may be used.
The results of the VNT are expressed as the reciprocal of the initial serum dilution at which half the inoculated cell cultures (50 % end point) fail to show viral replication (no specific labelling). A point between two dilution levels is estimated. The final dilution system is based on the actual dilution of serum during the neutralisation reaction, i.e. after addition of virus, but before adding the cell suspension.
The VNT for the detection of antibodies against BVD virus and BD virus follow the same principals mentioned above and are conducted for the differential diagnosis of classical swine fever.
The competitive or blocking ELISA is usually based on monoclonal antibodies. If the serum sample contains antibodies to classical virus, the binding of a selected peroxidase-conjugated monoclonal antibody to virus antigen will be inhibited resulting in a reduced signal.
In non-competitive ELISA the binding of serum antibodies to antigen is measured directly using peroxidase-conjugated anti-pig antibodies.
The ELISA to be used for the serological diagnosis of classical swine fever must recognise all reference sera from the convalescent pigs. All results obtained with the reference sera must be repeatable. It is further recommended that they detect all positive sera from the early phase and to show a minimum of cross-reactions with the sera from pigs infected with ruminant pestiviruses.
The results obtained with the reference sera from pigs in the early phase of infection give an indication of the sensitivity of the ELISA.
The ELISA must ensure identification of all classical swine fever infections at the convalescence stage and need to be as free as possible from interference by cross-reacting antibodies to ruminant pestiviruses.
The samples already collected from this holding must be re-tested by VNT by comparative end point titration of the neutralising antibodies against classical swine fever virus and ruminant pestiviruses.
the measures referred to in Article 4(2) of Directive 2001/89/EC shall continue to apply;
further investigations are carried out as quickly as possible to confirm or rule out classical swine fever, in accordance with Chapter IV.
In the framework of this further sampling, the pigs already sampled and tested shall be re-sampled for a comparative serological testing with the previously collected samples to detect sero-conversion for classical swine fever virus or for ruminant pestiviruses, if any.
If these further checks and tests do not allow classical swine fever to be confirmed, the measures referred to in Article 4 of Directive 2001/89/EC may be lifted.
This discriminatory test is sensitive and specific (14) . However, also pigs which have become infected with Pestiviruses other than classical swine fever virus, such as BVD virus and BD virus, will also react Erns-positive. Furthermore, the sensitivity of the test is not ideal, as some marker-vaccinated and then infected animals may not react Erns-positive.
The data currently available suggest that the discriminatory test cannot be reliably used to test serum samples from feral pigs.
A result is obtained by comparing the optical density (OD) in wells containing test samples with those of wells containing the negative and positive controls.
The discriminatory test is designed to verify the presence or absence of classical swine fever virus circulation on a pig population vaccinated with a marker vaccine. The available data suggest that it can be successfully used for that purpose on herd bases, but it cannot reliably exclude that individual pigs are infected with classical swine fever virus. In particular, the specificity of the discriminatory test might not be sufficient to reliably discriminate marker vaccinated pigs from infected pigs in case of vaccination of adult pigs. In case of doubtful results, however, the pigs in question must be slaughtered or killed in a humane way in accordance with Directive 93/119/EC and their organs tested for classical swine fever virus. Virus isolation and the PCR are the most suitable tests for that purpose.
These aspects have to be taken into full account when designing an emergency marker-vaccination strategy and then interpreting the results of a classical swine fever virus survey onto the marker-vaccinated population.
The procedure for sampling and testing the vaccinated pig population before lifting the restrictions to be applied in the vaccinated area in accordance with Article 19 of Directive 2001/89/EC, should depend on the age of the vaccinated pigs, the category of pigs (fattening/slaughter, breeding) and the desired level of safety as regards the absence of virus circulation in the population.
Details on the procedure for sampling and testing shall therefore be laid down in the emergency vaccination plan to be submitted to the Commission pursuant to Article 19(3) of Directive 2001/89/EC."]
Additional requirements | Minimal requirements | |
---|---|---|
General environment | Normal atmospheric pressure Double HEPA filtration of exhaust air. Dedicated rooms, used exclusively for classical swine fever diagnostic procedures. | Normal atmospheric pressure. Dedicated rooms limited to defined procedures. |
Laboratory clothing | Complete change of clothes on entry. Laboratory clothing used only in the classical swine fever virus unit. Disposable gloves for all manipulations of infected material. Clothing sterilised before removal from unit, or washed within unit. | Dedicated outer clothing used only in the classical swine fever virus unit. Disposable gloves for all manipulations of infected material. Outer clothing sterilised before removal from unit, or washed within unit. |
Control of personnel | Entry to unit limited to named, trained personnel. Wash and disinfect hands on leaving unit. Personnel not permitted near pigs for 48 hours after leaving unit. | Entry to unit limited to named, trained personnel. Wash and disinfect hands on leaving unit. Personnel not permitted near pigs for 48 hours after leaving unit. |
Equipment | Biological safety cabinet (Class I or II) used for all manipulations of live virus. Cabinet should have double HEPA filtration of exhaust air. All equipment needed for laboratory procedures to be available within the dedicated laboratory suite. |
Requirements | |
---|---|
General environment | Negative pressure controlled ventilation. Double HEPA filtration of exhaust air. Facility for complete fumigation/disinfection at end of experiment. All effluents treated to inactivate classical swine fever virus (heat or chemical). |
Laboratory clothing | Complete change of clothes on entry. Disposable gloves for all manipulations. Clothing sterilised before removal from unit, or washed within unit. |
Control of personnel | Entry to unit limited to named, trained personnel. Full shower on exit from unit. Personnel not permitted near pigs for 48 hours after leaving unit. |
Equipment | All equipment required for animal procedures to be available within the unit. All materials to be sterilised on removal from unit or, in the case of animal samples, to be double wrapped in leakproof container which is surface disinfected for transport to the classical swine fever laboratory. |
Animals | All animals to be slaughtered before leaving the unit, post mortem examinations to be completed within the bio-safe area, and carcasses incinerated on completion of examinations. |
OJ L 316, 1.12.2001, p. 5.
OJ L 47, 21.2.1980, p. 11.
When deciding the number of samples to be taken for laboratory testing, the sensitivity of the tests that will be used shall also be considered. The number of animals to be sampled shall be higher than the one indicated in this Manual, if the sensitivity of the test to be used is not very high.
Singleton reactors may have titres of virus neutralising antibodies ranging from borderline (which is more often the case) to strongly positive. On re-sampling, singleton reactors may show a decreasing or constant titre. In general only few pigs in a herd give rise to these false/positive reactions.
If pigs have been vaccinated against classical swine fever with a conventional vaccine they can be found seropositive due to the vaccination alone, or due to a silent infection in vaccinated animals.
Under certain circumstances up to 10 % of the pigs within a herd may have antibodies against ruminant pestiviruses causing bovine viral diarrhoea and border disease. For example, when pigs have direct contact with cattle or sheep infected with BVD virus or BD virus, or when pigs have contact with materials contaminated with ruminant pestiviruses.
In all of the current serological tests for classical swine fever a small proportion of sera give false/positive results either due to the lack of specificity of the test-system or due to sera from the singleton reactors.
In certain cases, e.g. when classical swine fever is suspected in a holding with a limited number of young pigs, the proportion of infected sows may be very small. In these cases a higher number of sows must be sampled.
However, if the derogation provided in Article 6(1) of Directive 2001/89/EC has been applied, sampling must concern the sub-units of the holding where pigs have been killed, without prejudice to the further examinations and sampling to be carried out on the remaining pigs in the holding, which shall be carried out in accordance with the instructions of the competent authority.
However, if the competent authority has limited the application of preventive killing only to the part of the holding where the pigs suspected of being infected or contaminated with classical swine fever virus were kept, in accordance with Article 4(3)(a) of Directive 2001/89/EC, sampling must concern the sub-units of the holding where this measure has been applied, without prejudice to the further examinations and sampling to be carried out on the remaining pigs in the holding, which will be carried out in accordance with the instructions of the competent authority.
In certain cases, e.g. when classical swine fever is suspected in a holding with a limited number of young pigs, the proportion of infected sows may be very small. In these cases a higher number of sows must be sampled.
The Community Reference Laboratory has an unlimited permit to receive diagnostic samples and classical swine fever virus isolates. Copy of the import permit may be requested from this laboratory before transport and attached in an envelope to the outside of the package.
Several Classical swine fever ELISA antigen are commercially available, which are validated with different types of samples.
[In accordance with the results of a study carried out by the Community reference laboratory for classical swine fever and the national classical swine fever laboratories, the sensitivity of the discriminatory test is about 94 % and the specificity is about 98 %.]