Retrospective analysis of the oral immunisation of wild boar populations against classical swine fever virus (CSFV) in region Eifel of Rhineland-Palatinate

Abstract

In the present study the effect of control measures implemented during the classical swine fever (CSF) epidemic in wild boar in the Eifel region of the German federal state of Rhineland-Palatinate from 1999 to 2005 was assessed. During the first 3 years after official confirmation of virus detection these measures comprised intensive hunting, especially of young animals and hygiene measures. Subsequently oral immunisation (o.i.) using a modified live virus vaccine was introduced as an additional control tool. All shot wild boar from the restricted area were tested virologically and serologically for CSF. The laboratory results from over 110,000 animals accompanied by information about age, gender and geographical origin of the animals were collected in a relational database. In total about 82% of all virologically positive wild boars were piglets, thus confirming the importance of this age group in the perpetuation of the epidemic. An analysis of the hunting bag showed that piglets were underrepresented compared to older animals throughout the eradication programme. This finding indicated that hunters did not comply with the control strategy of intense targeting of young animals. Before as well as after the implementation of o.i. a significantly higher virological prevalence and a significantly lower serological prevalence were observed in piglets compared to yearlings and adults. Shortly after the beginning of the vaccination campaign in February 2002 CSFV prevalence decreased significantly whereas the serological prevalence increased markedly in all age classes. In order to test the influence of age and vaccination on the serological prevalence a logistic regression model was used. Our results strongly suggest that under the field conditions in the Eifel region vaccination against CSFV had a crucial influence on the increase of seroprevalence rate and the elimination of CSFV. The last virus-positive pig was found 13 months after start of o.i.