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| | Wild boar act as a reservoir of CSF infection, and so control must also be aimed at this population. As well as adequate surveillance, this involves utilising knowledge about factors influencing CSF epidemiology such as wild boar behaviour and population dynamics, and the influence of hunting strategies. Wild boar vaccination schemes are currently being undertaken in parts of Europe using baits containing marker vaccines. | | Wild boar act as a reservoir of CSF infection, and so control must also be aimed at this population. As well as adequate surveillance, this involves utilising knowledge about factors influencing CSF epidemiology such as wild boar behaviour and population dynamics, and the influence of hunting strategies. Wild boar vaccination schemes are currently being undertaken in parts of Europe using baits containing marker vaccines. |
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| − | ===Vaccination===
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| | Where CSF is endemic vaccination is effective. there are now gene deletion marker vaccines available and ELISA tests an be used to differentiate vaccinated from infected animals. | | Where CSF is endemic vaccination is effective. there are now gene deletion marker vaccines available and ELISA tests an be used to differentiate vaccinated from infected animals. |
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| − | In principle, emergency vaccination is in agreement with EU legislation (Anonymous,
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| − | 1980). Requirements related to emergency vaccination campaigns against CSF virus have
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| − | been de®ned in the document `Guidelines for a Classical Swine Fever Emergency
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| − | Vaccination Programme' (Anonymous, 1994). However, by using conventional vaccines
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| − | and applying the mentioned guidelines, the Scienti®c Veterinary Committee of the
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| − | Commission has calculated that vaccinated animals would be excluded from the market
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| − | for up to 600 days (Anonymous, 1997). This is economically unacceptable and so far
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| − | emergency vaccination has never been used.
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| − | With the development of a ®rst generation marker vaccine against CSF the possibility
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| − | of an amendment of the existing EU emergency vaccination regulations seems feasible. A
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| − | restricted application of a marker vaccine would require extensive serological testing in
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| − | the vaccinated population in order to detect hidden ®eld virus infections. At present no
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| − | marker vaccine has been licensed within the EU and EU Member States demand welldocumented
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| − | data on the safety and ef®cacy of the vaccine before its potential use in
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| − | emergency situations. It is understood that the criteria for the use of the marker vaccine
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| − | will be very stringent. Provided that all safety requirements are met, the period of
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| − | exclusion from the market could be considerably shortened at least for pig products after
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| − | a CSF outbreak (Anonymous, 1997). As soon as marker vaccines are suf®ciently
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| − | investigated and licensed, the `Guidelines for a Classical Swine Fever Emergency
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| − | Vaccination Programme' (Anonymous, 1994) are to be amended. The possible use of an
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| − | emergency vaccination with marker vaccines is expected to avoid the ethically
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| − | questionable and expensive large scale pre-emptive slaughter of pigs. Thereby, the
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| − | public acceptance of the eradication policy will increase and costs will decrease. Under
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| − | these circumstances the use of emergency vaccination using marker vaccines could be a
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| − | useful tool of the non-vaccination policy.
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| − | From the beginning of the century attempts have been made to develop vaccines
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| − | against CSF. However, the safety and ef®cacy of the ®rst generations of vaccines were
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| − | poor. In the 1940s ®rst experiments were made to attenuate CSFV by adapting it to
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| − | rabbits (Baker, 1946; Koprowski et al., 1946). After initial setbacks, this development
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| − | ultimately led to a very ef®cient and safe generation of live vaccines. Most attenuated
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| − | vaccines are based on the China-strain (C-strain) of lapinized CSF virus. C-strain
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| − | vaccines were and are still being used world-wide for the control of CSF in domestic pigs.
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| − | It is also used at least on an experimental basis for the oral immunisation to control CSF
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| − | in wild boar (Kaden et al., 2000). C-strain vaccines induce high titres of neutralising
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| − | antibodies and they are safe when used on pregnant animals. Their ef®cacy is
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| − | demonstrated by the observation that vaccinated pigs are protected against infections with
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| − | virulent CSF virus as early as ®ve days after vaccination. The animals are immune
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| − | throughout their economic life. However, with respect to today's global trade policy there
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| − | is a severe disadvantage in using live attenuated vaccines against CSF: Vaccinated and
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| − | ®eld-virus-infected animals cannot be distinguished because the antibody pattern induced
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| − | by the vaccine virus resembles that of reconvalescent animals.
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| − | A way out of this dilemma may be the development and use of so-called marker
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| − | vaccines, e.g., subunit vaccines consisting of single viral surface proteins, which are suf-
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| − | ®cient for the induction of protective immunity. At present two subunit vaccines containing
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| − | the viral glycoprotein E2 are under scrutiny. The respective gene is expressed in baculoviruses
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| − | grown in insect cells (Van Rijn et al., 1996). Since these cells are able to glycosylate
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| − | proteins, the resulting viral glycoprotein is expressed in a `natural'way.CSF subunit vaccines
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| − | are safe and so far their protective potency is promising, though inferior to live vaccines.
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| − | Vaccinated animals may be distinguished from infected pigs using an ELISA based on a
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| − | different viral protein as diagnostic antigen, e.g., the surface glycoprotein Erns or the
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| − | nonstructural protein NS2-3. However, not all criteria for the emergency use of marker
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| − | vaccines are well de®ned yet, and the technical merits of these vaccines have not yet been
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| − | established. More data are expected to be available during the year 1999.
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| − | Technically there is the potential for further improving CSF marker vaccines by
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| − | developing, e.g., viral vector vaccines (RuÈmenapf et al., 1991; Van Zijl et al., 1991; Hooft
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| − | van Iddekinge et al., 1996), DNA vaccines and molecularly altered infectious cDNA
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| − | clones of CSF virus (Meyers et al., 1996, Moormann et al., 1996, Ruggli et al., 1996).
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| | ==Links== | | ==Links== |