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==Treatment==
 
==Treatment==
====Control====
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*'''NOTIFIABLE''' disease
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The control policy for CSF depends on the incidence and prevalence of the infection in
*'''Vaccination''' (live attenuated) in endemic countries:
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the domestic and wild pig populations, respectively. In countries with CSF endemic in
**Parts of EU are using vaccinated bait to control spread in wild boar population
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domestic pigs it is common practice to vaccinate against the disease, thereby, avoiding
**Vaccination does not curtail spread: marker vaccine needed to distinguish virus exposure from vaccine-induced antibody
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serious losses. However, the simultaneous eradication of ®eld virus is improbable because
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serological methods are no longer applicable for the detection of ®eld virus infections. It
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is acknowledged that ®eld virus may be hidden under a `blanket' of general vaccination.
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Taking this risk into account, importing countries in general do not allow the introduction
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of pigs or pig products from countries that vaccinate against CSF. The preventive
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measures adopted by the EU for trade with Third Countries stipulate that live pigs and
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fresh pig meat can only be imported from regions or countries where no CSF has
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occurred for 12 months and no vaccination against CSF was applied during the same
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period. Nevertheless a policy of consistent and systematic prophylactic vaccination in
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endemic situations may ultimately lead to a favourable starting point for a non
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vaccination policy and the eradication of the virus. After the cessation of general
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vaccination, eventual local outbreaks of residual ®eld virus must be dealt with by strict
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measures to ensure prevention of virus spread and eradication of the virus.
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Based on the above mentioned disadvantages of vaccination and a cost bene®t analysis
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the EU banned vaccination against CSF at the end of the 1980s. Whereas most
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neighbours of the EU have also adopted a similar policy, vaccination is allowed and
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mostly routinely applied by many Central and Eastern European countries (Edwards
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et al., 2000). In some of the latter countries only sick or clinically suspect animals are
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destroyed in case of CSF outbreaks whereas all other animals of the infected herd, herds
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in the neighbouring area and contact herds are vaccinated.
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In case of an outbreak of CSF, all EU Member States and the other Western European
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countries execute eradication measures according to the Council Directive 80/217/EEC
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(Anonymous, 1980; Edwards et al., 2000). These are based on stamping out
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(depopulation) of infected pig herds and possibly infected contact or (partially)
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neighbouring herds, epidemiological investigations, clinical and virological investigations,
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movement restrictions for live pigs, pig meat and other vectors which can transmit
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CSF within zones surrounding the infected farm and restrictions on contact farms outside
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these zones (Anonymous, 1980). Especially in areas with dense pig populations very
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high numbers of pigs had to be destroyed in the course of the eradication measures
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dealing with the outbreaks mentioned above. Only a minority of animals were killed due
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to direct involvement with the infection. Most of the pigs had to be killed because of
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welfare measures. The direct and indirect costs of recent CSF outbreaks in several EU
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Member States so far amount to several billion Euro, and in the course of the CSF
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epidemic in the Netherlands in 1997 approximately 10 million pigs were destroyed
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(Saatkamp and Horst, 2000; Stegeman et al., 2000). Whereas in areas with a low density
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pig population, the present control policy works very well it may well be questioned
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whether it is sustainable in areas with a high density of pigs. There is a general consensus
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that a number of measures must be introduced in order to reduce the vulnerability of
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regions at risk, e.g., structural changes in the pig industry including trade. However,
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implementation of appropriate programs might be dif®cult. Several parties, notably some
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V. Moennig / Veterinary Microbiology 73 (2000) 93±102 99
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national farmers' associations requested the reintroduction of a general or at least
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regional vaccination.
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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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A still unresolved problem is the control of CSF in wild boar (Laddomada, 2000).
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Both the prolonged persistence of virus in wildlife populations and the constant threat
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of domestic pig holdings in the respective areas require an ef®cient control strategy.
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Comprehensive information about the current situation in wild boar populations
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is essential and new strategies have to be devised. They have to take into account
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current knowledge about factors in¯uencing CSF epidemiology, e.g., wild boar
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behaviour; population dynamics; in¯uence of hunting strategies; in¯uence of geographic
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pro®les.
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An ef®cient surveillance system must be an integral part of the control strategy. The
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EU Commission has held a workshop dedicated to this topic (Anonymous, 1998) and a
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working group of the Scienti®c Committee on Animal Health and Animal Welfare will
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prepare a recommendation.
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===Vaccination===
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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).
    
==Prognosis==
 
==Prognosis==
6,502

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