Spatio-temporal trends and risk factors for Trichinella species infection in wild boar (Sus scrofa) populations of central Spain: a long-term study

In south-central Spain, the harvest of Eurasian wild boar (Sus scrofa) has increased significantly during recent decades in association with more intensive management actions to increase hunting yields and with consequent effects on the health status of the wild boar populations. We investigated the spatio-temporal trends and the risk factors related to the prevalence of Trichinella spp. in wild boar in order to obtain the annual probability of occurrence for these parasites in the Ciudad Real province of south-central Spain. Based on muscle samples collected during the hunting seasons from 1998/1999 to 2009/2010, the mean prevalence for Trichinella spp. in 95,070 wild boar was 0.2% (95% confidence interval 0.17-0.23). A subsample of 1,432 wild boar was also tested by ELISA. No correlation was observed between the prevalence of infection detected by serology and by the artificial digestion of muscle. The presence of Trichinella infections in wild boar showed a decreasing trend during the study period and was negatively related with fenced wild boar populations. The predicted 'favourability' for Trichinella infections disappeared almost completely after the 2006/2007 hunting season. Risk maps based on biogeographical tools showed, however, that most hunting estates presented favourable risk factors for these parasites during at least one of the hunting seasons studied.