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| | Although antigen detection methods have largely replaced serology in the diagnosis of acute classical swine fever outbreaks, CSFV serology is important for disease surveillance, particularly in wild boar. A virus neutralisation test is the most sensitive and specific form of CSFV serology, and involved incubation of test sera with a CSFV to neutralise any anti-CSFV antibodies present. However, the virus neutralisation test takes several days, and so an ELISA test may be used when large numbers of samples must be processed. | | Although antigen detection methods have largely replaced serology in the diagnosis of acute classical swine fever outbreaks, CSFV serology is important for disease surveillance, particularly in wild boar. A virus neutralisation test is the most sensitive and specific form of CSFV serology, and involved incubation of test sera with a CSFV to neutralise any anti-CSFV antibodies present. However, the virus neutralisation test takes several days, and so an ELISA test may be used when large numbers of samples must be processed. |
| | | | |
| − | ==Treatment== | + | ==Treatment== |
| − | In the UK and most parts of Europe there is a slaughter policy for control and eradication. The infected farm is isolated and movement restrictions are placed on pigs in the designated infected area. Disinfection of equipment, footwear, vehicle tyres etc are undertaken to prevent spread of infection. Thorough upstream and downstream tracing is done to try and locate the source of infection and any secondary outbreaks that may have arisen (or be anticipated) due to indavertent spread of infection from the primary outbreak. Under the Movement of Pigs Order, the 21 day rule (no movement of pigs off a farm within 21 days of the pigs arriving at the farm, unless they are consigned for slaughter) has proved to be very helpful in limiting the spread of notifiable diseases when oubtreaks occurr. Once the herd is slaughtered there is throrough cleaning and disinfection of the building, paths etc. Sodium hydroxide, washing soda and formalin are all effective.
| + | |
| | + | Classical swine fever is controlled rather than treated. The policy for control depends on the prevalence of infection in the pig population of a particular country: where CSF is endemic vaccination strategies are commonly used, but outbreaks in the normally CSF-free of the EU are controlled by a slaughter policy. This policy aims for eradication of CSFV by "stamping out" infected and neighbouring herds and contacts, imposing movement restrictions and investigating the source and spread of the outbreak. Equipment, footwear and other fomites must be disinfected, and once a herd is depopulated farm buildings and other areas are throughly cleaned and disinfected. Effective disinfectants include sodium hyrdoxide, formalin and washing soda. |
| | + | |
| | + | 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. |
| | + | |
| | + | ===Vaccination=== |
| | + | 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. |
| | | | |
| − | The control policy for CSF depends on the incidence and prevalence of the infection in
| |
| − | the domestic and wild pig populations, respectively. In countries with CSF endemic in
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| − | domestic pigs it is common practice to vaccinate against the disease, thereby, avoiding
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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, | | In principle, emergency vaccination is in agreement with EU legislation (Anonymous, |
| | 1980). Requirements related to emergency vaccination campaigns against CSF virus have | | 1980). Requirements related to emergency vaccination campaigns against CSF virus have |
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| | these circumstances the use of emergency vaccination using marker vaccines could be a | | these circumstances the use of emergency vaccination using marker vaccines could be a |
| | useful tool of the non-vaccination policy. | | useful tool of the non-vaccination policy. |
| − | 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===
| |
| − | 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. Wild boar vaccintion schemes are being undertaken in parts of Europe using baits containing gene delted or recombinant vaccines.
| |
| | From the beginning of the century attempts have been made to develop vaccines | | From the beginning of the century attempts have been made to develop vaccines |
| | against CSF. However, the safety and ef®cacy of the ®rst generations of vaccines were | | against CSF. However, the safety and ef®cacy of the ®rst generations of vaccines were |