Understanding the factors that modulate the transmission dynamics of Aujeszky's disease virus in wild boar in enzootic scenarios

Laia Casades-Martí, David González-Barrio, Lara Royo-Hernández, Iratxe Díez-Delgado, Francisco Ruiz-Fons

Aujeszky's disease virus (VEA) circulates enzootically in the wild boar in the Iberian peninsula, constituting a threat to the official eradication of EA in extensive pigs in Spain. Understanding the dynamics of VEA infection and the factors that condition its transmission in wild boar populations would be of great help in preventing virus transmission in the domestic wild boar-pig interface. This work studies the dynamics of oar VEA infection and analyzes several important hypotheses to estimate the underlying factors of such a dynamic. Serums (by ELISA) were analyzed for this purpose; No. 971) and oropharyngeal tonsila samples (by PCR; No. 549) of wild boars sampled over 11 consecutive years in southwestern Spain. Hypotheses were touted that population immunity against low VIrulence strains of VEA circulating in the wild boar modulates the risk of infection with this virus (H1) and that estimating the rate of INFECTION by VEA in orpharyngeal cough samples could be a good indicator of viral infection pressure in the population (H2). To this end, binary logistic regression models were constructed that analyzed the effect of population and individual factors – including various predictors of VEA's population immunity – on the annual risk of new virus infections and on viral infection rate in oropharyngeal tonsilas. The main premise of H1 was based on a negative association between the proportion of HIV-positive individuals versus the VEA in the population (considered as a potential indicator of population immunity) and the risk of infection of susceptible individuals, but such relationship was, on the other hand, positive and H1 was rejected. If the rate of VEA infection in tonsilas was a good indicator of viral infection pressure in the population, it would have been positively related to population seroprevalence and the risk of new infections. However, this was not the case and H2 was also rejected. We conclude that the low virulence strains of the VEA are transmitted, despite their low pathogenic capacity for the suidos, similar to the high virulence strains and therefore HIV-positive animals are potential viral excretors and antibodies infection by these strains does not slow the reactivation of latent infections and the transmission of VEA. However, we note that VEA infection is dynamic in wild boar populations and that the risk of infection varies considerably between consecutive years, which is associated with the prevalence of viral infection and, probably, with the dynamics population of the wild boar.

Reference:

Casades-Martí L., González-Barrio D., Royo-Hernández L., Díez-Delgado I., Ruiz-Fons F. Dynamics of Aujeszky's Disease Virus in Infection Wild Boar in Enzootic Scenarios. Transboundary and Emerging Diseases, DOI: https://doi.org/10.1111/tbed.13362. Available online at: https://onlinelibrary.wiley.com/doi/abs/10.1111/tbed.13362.

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