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Questions and answers on Classical Swine Fever
Commission Européenne - MEMO/01/422 05/12/2001
Brussels, 5 December 2001
Questions and answers on Classical Swine Fever
What is Classical Swine Fever ?
Classical Swine Fever (CSF) is a highly contagious viral disease that affects domestic pigs and wild boar. It causes serious disease and very high mortality in infected animals, up to 90% in young infected animals. The infection is highly contagious and transmitted through direct or indirect contact between animals. The virus is transmitted via the blood, tissues, secretions and excretions of sick and dead animals. Pigs can become infected by ingestion, inhalation, genital (semen) infection or by contamination of abrasions. In addition congenitally infected piglets are persistently viraemic and shed the virus for months.
How does CSF spread?
CSF mainly spreads by contact with infected pigs. It can however also spread from one farm to another via indirect contact involving farm visitors, contaminated vehicles, farm equipment, clothing, instruments etc., or by insufficiently treated contaminated swill (kitchen waste) fed to pigs, and contaminated fresh pig meat and meat-based products. The disease can be transmitted over long distances via contaminated materials or meat (products). Over the past ten years it has become evident that in some areas of Europe wild boar harbour the CSF virus and are a source of infection of domestic pigs.
NO, Does CSF pose any risk to humans ?
There is no known risk that the CSF virus may cause any disease in humans.
What is done to prevent outbreaks of classical swine fever?
The Community has set strict rules on imports of live pigs and of fresh and cured pig meat to prevent the introduction of classical swine fever. Imports are authorised only if the country or region of origin is CSF-free and its veterinary services are deemed to have the ability to detect swine fever and to react to it appropriately. Importing countries or regions must also fulfil the other animal and public health requirements of Community legislation.
What is the policy in case of outbreaks of CSF?
Current policy on CSF aims to eradicate the disease from the Community. This means that in case of outbreaks a stamping-out policy is applied, involving the slaughtering of all pigs on affected farms, the destruction of cadavers and bedding, and disinfection of farms in the designated zone of infection. Movements of pigs into and out of the infected zone are controlled, an epidemiological investigation is made to trace the sources and spread of the infection, and special surveillance measures inside the infected zone are taken.
What is the policy on vaccination against CSF?
Since the 1990's a non-vaccination policy is in force. Vaccines may only be used in emergencies, after confirmation of the disease, if there is a risk of further serious disease outbreaks. The validity of this policy was confirmed by the Scientific Committee in 1997.
Following infection with CSF virus, vaccinated animals usually do not show clinical signs of disease, e.g. they are protected against it. However, the possibility that vaccination leads to a "silent" circulation of virus in a vaccinated but not fully immune pig population induces scientists to be cautious on the use of vaccines as an effective mean to eradicate the disease. In addition, the restrictions to trade, which are applied in the areas where the vaccine has been used in order to prevent any virus spreading, may make vaccination not attractive.
In case of a generalised preventive vaccination policy, vaccination costs must also be taken into account, given that the pig production in the Community amounts at about 200 million pigs per year.
What are marker vaccines, what is their advantage ?
Marker vaccines are vaccines that can give pigs protective immunity to CSF which can potentially be distinguished from the immune response caused by a natural infection by means of a laboratory test. The advantage of marker vaccines is that they would allow distinguishing infected pigs (which may spread the disease to other pigs, even if they do not show signs of disease) from vaccinated pigs. Thus the trade restrictions currently applicable to vaccinated pigs and their products would no longer be necessary.
Why are marker vaccines not used as yet?
Two new CSF vaccines that posses specific features facilitating their potential use as marker vaccines by inducing immunity only against one of the virus' proteins have recently been developed and have been authorised for use as CSF vaccine by the European Medicinal products Evaluation Agency (EMEA).
A large-scale laboratory trial, which was carried out in 1999 with the financial support of the Commission in 1999, has however demonstrated that, despite their special features, a suitable test method for distinguishing the presence of these marker vaccines from the real infection is not yet available. Research to develop such a test method is under way and progressing.
In accordance with the new Council Directive on the control of classical swine fever (see below) the use of these vaccines will be possible in case of an emergency, once these laboratory tests will be developed and validated.
What are the economic consequences of outbreaks?
Classical swine fever is incompatible with pig farming in a modern society. In case of an outbreak appropriate control measures must be adopted. These include restrictions on trade in accordance with the international standards and with Community legislation. An outbreak of CSF impairs internal and international trade and the movement of pig and pig products and the overall economic consequences may be very serious.
For example, the overall cost for the Community budget of the very serious epidemic occurred in the Netherlands in 1997-1998 amounts at about 600 million EUROs. The overall costs and losses of this epidemic have been estimated in about 2 billion EUROs.
Is there any revision of existing CSF policy foreseen?
The Council of Agriculture Ministers has on 23 October 2001 adopted a new Directive on the control of Classical Swine Fever, following a proposal put forward by the European Commission in September 2000 (COM(462)final). The new Directive consolidates existing rules and adapts them to new scientific insights and progress, and to experience gained in recent years with CSF outbreaks in areas of high density pig farming.
The new rules continue the non-vaccination policy based on the culling of all pigs in farms infected with CSF, but foresee a possible wider use in future of vaccination in emergencies through the use of marker vaccines. Marker vaccines will, once appropriate test methods have been developed and approved, allow distinguishing vaccinated pigs from pigs that are actually infected. Their use will need to be authorised by the Commission on a case-by-case basis and be subject to strict evaluation and control. Specific decisions on trade restrictions to apply to farms that have used the marker vaccines will also need to be taken on a case by case basis.
The new Directive prohibits the feeding of swill to pigs, and further refines and reinforces existing control measures, for example by extending notification obligations and requiring an in-depth epidemiological investigation after outbreaks of CSF. It also provides for the possibility of vaccinating feral pigs in case of CSF outbreaks, and introduces more detailed provisions on contingency plans. The new rules will become applicable as of 1 November 2002
How effective have the control measures on CSF been over the past years ?
On the whole, during the 1980's several thousand outbreaks of CSF occurred in the Community. Since the 1990's, when the non-vaccination policy was introduced the trend has been towards a considerably lower level of presence of the disease, until a major epidemic occurred in 1997/98 (a total of about 600 outbreaks). The situation has largely improved over the past few years, but the disease persists in wild boar in some areas of the Community and in some bordering countries. It therefore continues to present a serious threat to pig farming in the Community, in particular in areas with a high density of pigs where it can be very difficult to get outbreaks under control.
How many outbreaks of classical swine fever have there been over the past years?
The last major swine fever epidemic occurred in 1997/1998, with outbreaks in Germany, Belgium, Italy and notably in Spain and the Netherlands. In the Netherlands alone between 10 and 11 million pigs (in over 400 outbreaks) were slaughtered and destroyed during this epidemic and more than 1 million 1.7 million in Spain (in about 100 outbreaks). In the following two years, the disease has shown a clear declining trend (see table attached).
[Graphic in PDF & Word format]
HOWEVER, the UK COUNTED 16 outbreaks in 2000 caused by a strain of the CSF virus originating from outside the Community, which was most likely introduced in the UK via contaminated waste food.
In 2001 outbreaks of CSF have occurred in Spain (29), probably due to a virus introduction from outside the Community, and in Germany (5) and Italy (5, localised on the island of Sardinia), in areas where the disease occurs in wild boar.
Is intensive pig farming a cause of classical swine fever?
No, intensive pig farming is not a cause of CSF, as shown by the frequent occurrence of CSF in small family farms and in free ranging pigs which may come in contact with infected wild boar or with contaminated swill or kitchen waste, as was probably the case in the UK.
However, CSF causes major problems in areas with a high density of pigs when it occurs because of the many potential risk factors present in such areas.
The occurrence and persistence of classical swine fever in the wild boar population has been a cause for concern in some areas of Germany, Italy, France and Austria, although the overall situation has improved when compared with 1999.
What is the state of play regarding the recent CSF outbreak in Spain?
A total of 29 CSF outbreaks have occurred in Spain from June through September 2001, in the north-eastern part of the country (Catalunya, Valencia and Castilla-La Mancha). The Commission has taken several measures safeguard clauses restricting animal movements and trade in pigs and certain pig products and from the CSF affected areas. The measures were adapted as necessary to take account of the evolving situation. As of early 15 November 2001, no restrictions on trade and animal movements are any longer applied.
The Spanish authorities have implemented a national sero-surveillance scheme in pig farms to identify and/or exclude any presence of disease.
What is the state of play with respect to the current CSF outbreak in Germany?
A total of 5 outbreaks of CSF have been detected in Germany in 2001, two of them in Lower Saxony in June-July and three in Rheinland-Palatinate in October.
What is the origin of the CSF outbreak in Germany?
The virus responsible for these outbreaks is of the same type as the one that has been identified in the wild boar in these areas. These findings indicate that the origin of the outbreaks is the local wild boar population.
What measures have been taken to deal with the CSF outbreak in Germany?
A CSF surveillance and control programme, including large-scale testing of domestic pigs and wild boar, is in place throughout Germany. Special disease control measures are in place in the areas where CSF persists in the wild boar population. They include:
- mandatory testing for CSF of wild boar shot or fund dead in the relevant areas;
- a prohibition on the marketing of meat from the CSF-negative wild boar beyond the local area;
- hunting strategies to reduce the susceptible wild boar population by targeting young animals;
- strict surveillance and rigorous restrictions on the movements of domestic pigs in the areas where CSF occurs in the wild boar population, including a prohibition to move domestic pigs from these areas to other Member States.
In addition, vaccination trials of the wild boar population are on-going in different parts of Germany. These trials seem to be giving favourable results in some areas, notably in Mecklenburg-WesternPomerania. Although these measure have not always achieved the eradication of the disease from the wild boar, they have been successful in limiting the number of disease outbreaks in domestic pig farms and in preventing the spread of disease from the zones where the virus persist in the wild boar.
What is the state of play in the candidate countries?
CSF has been shown to be occur and persist in the wild boar population of some of the candidate countries. The issue is dealt with within the framework of the accession negotiations. Candidate countries are to provide detailed information on the presence of CSF, and of the measures in place to monitor and control the disease in their domestic pigs and wild boar populations.
What are the rules on compensation for farmers and what has been the cost of recent outbreaks of CSF to the Community budget?
The Community reimburses the Member States for up to 50% of their expenditure incurred for the compensation of farmers whose animals were slaughtered and destroyed and for the costs of disinfection of the depopulated farms.
What is the Commission doing to prevent the slaughter of large numbers of animals ?
To prevent an outbreak of CSF from spreading, Community legislation requires that the national competent authorities enforce a contingency plan specifying the national measures for the rapid and efficient eradication of the outbreak. The potential efficacy of these plans has been the subject of a series of inspections by the Commission's Food and Veterinary Office.
The European Commission admits that it is be preferable to avoid the destruction of large numbers of animals as much as possible.. However, at present all experts agree that a rigorous stamping-out policy must be carried out immediately when an outbreak occurs, in particular in areas with a high density of pigs, as this is the best method to prevent a further disease spread and massive death of animals.
Furthermore, Community legislation does not exclude the use of emergency vaccination, where this proves necessary and effective.
What is the scientific state of play?
In its 1997 opinion on the control of classical swine fever the Scientific Committee on Animal Health and Anima Welfare (SCAHAW) strongly advocated a non-vaccination policy on CSF and recommended further studies on the development and use of marker vaccines. Such studies have since been carried out with the financial support of the Commission (see above).
The Scientific Committee on Animal Health and Anima Welfare (SCAHAW) has in its report of August 1999 on classical swine fever in wild boar recommended the implementation of some disease control measures that might lead to an improvement in the situation, notably by a selective reduction of the young wild boar population and by vaccination of wild boar populations.
Vaccination trials in wild boar are currently under way in some areas of Germany. So far, the results of these trials are encouraging. Nonetheless, several technical problems must still be solved before conclusions about the effectiveness of vaccination as an appropriate method to control and eradicate the disease in the wild boar can be drawn.
Annex 1: Outbreaks of classical swine fever 1980
Number of outbreaks of Classical Swine Fever
reported by Member States, 1980-1990 and 1990-2000