Dynamics of Aujeszky's disease virus infection in wild boar in enzootic scenarios

Aujeszky's disease (AD) virus is enzootic in Iberian wild boar, thus posing a threat to the official eradication of AD on extensive domestic pig farms in Spain. Understanding the dynamics and drivers of ADV infection in wild boar will help prevent viral transmission at the wild boar-pig interface. This study analyses the dynamics of ADV infection in wild boar and tests relevant hypotheses in order to identify drivers of ADV infection dynamics. Wild boar sera (N = 971) and oropharyngeal tonsils (TN, N = 549) collected over 11 consecutive years in south-western Spain were tested for ADV antibodies and DNA, respectively. We tested the hypotheses that population immunity modulates the risk of ADV infection (H-1) and that detecting ADV DNA in TN is a good proxy of the annual ADV infection pressure (H-2). This was done by building logistic regression models that were subsequently employed to test the influence of a series of host population and host individual factors-including predictors of ADV immunity in the population-on the annual risk of new ADV infections and on the presence of ADV DNA in TN. The premise of H-1 was that there would be a negative association between the proportion of ADV antibody-positive wild boar in a given year and the risk of ADV infection of naive individuals. There was, however, a positive association, and H-1 was, therefore, rejected. If detecting ADV in TN had been a good indicator of ADV infection pressure, a positive association with the proportion of ADV antibody-positive wild boar would have been found. However, this was not the case and H-2 was also rejected. We confirmed that ADV infection is a dynamic phenomenon. The risk of infection with ADV can change considerably between consecutive years, and these changes are positively associated with the proportion of infected wild boar in the population.