Zur Bekämpfung der Klassischen Schweinepest (KSP) bei Schwarzwild in Nordrhein-Westfalen
Contributor(s)Univ.-Prof. Dr. Karl-Hans Zessin
Dir. u. Prof. Dr. habil. Volker Kaden
Univ.-Prof. Dr. Karl Heinz Lahrmann
Keywords630 Landwirtschaft, Veterinärmedizin
630 Agriculture, Veterinary medicine
classical swine fever virus
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AbstractA retrospective analysis of the course and the eradication program of Classical Swine Fever (CSF) in wild boar populations in the state of North Rhine-Westphalia, Germany, between 2002 and 2007 was carried out. Its basis were data from questionnaires, which had to be filled out during the process of oral immunisation (o.i.) and from serological and virological findings derived from an international CSF database of hunted wild boars.
Learning from years of experience in the eradication of CSF using o.i. in Baden-Wurttemberg and other federal states, North Rhine-Westphalia incorporated o.i. as a further effective method into the CSF eradication program in addition to hunting and hygiene measures to combat epidemics, based on the eradication program of Rhineland Palatinate before the first CSF-virus (CSFV)-infection had been detected. Using a CSF attenuated live vaccine based on the “China-strain” (C-strain) in maize baits (RIEMSER Schweinepestoralvakzine, RIEMSER Arzneimittel AG, Greifswald, Isle of Riems), oral immunisation was performed as a continuous strategy using three double vaccination periods per year (except 2003).
The questionnaire data allowed an evaluation of the eradication procedure of o.i. In combination with the data from the CSF-database it provided the basis of causal research into the re-emergence of CSF in 2005.
Between 2002 and 2004, hunters had to fill out questionnaires on the distribution and placement of baits in each case. Questionnaire information was related to the nine concerned CSF-affected hunting communities and used for the assessment of other aspects such as respective soil conditions and meteorological data. Data from the CSF-database referring to serological and virological findings of all wild boars examined could also be classified according to the place where individual boars were killed or found dead and to their age. A descriptive analysis of the CSF-database serological data revealed a significant difference in the seroprevalence rates of different age groups. Piglets had low seroprevalences as opposed to sub-adults and adults. In addition, virusprevalence rates showed even greater differences between piglets and sub-adults as well as adults. The fact that virusprevalence is higher among the youngest age class underlines once again the crucial role of piglets in the perpetuation of a CSF-epidemic.
Significant differences between hunting communities of the hot-spot-area (hunting communities with the highest number of positive CSF virus detection) and the other hunting communities were assessed by statistical analysis of serological and virological data. The hot-spot-area consists of the hunting communities of Bad Münstereifel and Euskirchen.
The use of a conventional live vaccine did not allow distinguishing between antibodies resulting from field infection and vaccination. For that reason, the influence of o.i. could be evaluated only indirectly. In the near future, this differentiation could be brought about by the use of a DIVA-vaccine (differentiation between infected and vaccinated animals) in combination with a sensitive diagnostic technique. The influence of the herd immunity, however, could be verified. Also, the consequences of the missing summer immunisation of 2003 could clearly be ascertained.
Furthermore, the analysis of the questionnaire data allowed inferences on possible causes of the less effective vaccination campaigns from 2002 until 2004. Especially in the hot-spot-area of Bad Münstereifel several shortcomings in the distribution of baits were revealed. Furtheron, insufficient observations of animals and the wrong size of the vaccination zones constituted major problems.
The analysis of the hunting bag, classified for age groups and hunting communities, also shows that during the CSF eradication program, the quantity of pigs taken was not significantly increased as required; the proportion of piglets remained at an average of 54%.
The documentation of the course of the seroprevalence rates showed a significant increase in all age groups at the beginning of 2006, when the new immunisation phase had started. Differences in the seroprevalence rates between the piglets and the older though were maintained.
In conclusion: The re-emergence of CSF in the county of Euskirchen in 2005 was caused by multiple factors, including shortcomings in the execution of the o.i., especially in the hot-spot-area, a missing summer immunisation in 2003 and a far too small hunting bag to effectively reduce the wild boar population. However, for the control of epidemics, a o.i. strategy with three double vaccination periods per year in combination with hunting and hygiene measures is an appropriate method for CSF eradication in wild boar populations. An area extensive, long-term and individual strategy for planning and executing an immunisation program is required, into which hunters have to be involved by constant interaction with officials. After the successful eradication of CSF, a directed and long-term examination of hunted wild boars of defined age groups is essential for the prevention and early detection of CSF re-emergence. Due to directed examinations of wild boars in 2005, it was possible to detect such re-emergence and start eradication at an early stage. In the northern part of the Eifel (North Rhine-Westphalia) the crucial role of young wild boars (piglets) in the perpetuation of CSF was again underlinded. In future, all efforts to eradicate CSF will have to be focused on this age group.