Estimation of European wild boar relative abundance and aggregation: a novel method in epidemiological risk assessment

Abstract

Wild boars are important disease reservoirs. It is well known that abundance estimates are needed in wildlife epidemiology, but the expense and effort required to obtain them is prohibitive. We evaluated a simple method based on the frequency of faecal droppings found on transects (FBII), and developed a spatial aggregation index, based on the runs test statistic. Estimates were compared with hunting data, and with porcine circovirus and Aujeszky's disease virus seroprevalences and Mycobacterium tuberculosis complex and Metastrongylus spp. prevalence. The FBII and the aggregation index were correlated with the hunting index, but both of the former estimates correlated better than the latter with the disease prevalences. Hence, at least in habitats with high wild boar densities, the FBII combined with the aggregation index constitutes a cheap and reliable alternative for wild boar abundance estimation that can be used for epidemiological risk assessment, even outside the hunting season and in areas with no available data on hunting activities.

Fig. 1

Management effect on aggregation index, FBII, and hunting index.

Fig. 2

Spearman rank correlations between the prevalences of the four diseases, aggregation index, FBII and hunting index. Levels of significance of the statistical analysis: n.s., not significant; +P<0·05; ++P<0·01.

Fig. 3

Relationship between prevalence of infectious diseases and spatial aggregation in the European wild boar. The grey background represents the spatial distribution of the sum of prevalences of MTBC, PCV2 and ADV (darker means higher prevalence, 0–10, 11–50, 51–100, 101–150, >150). Circles represent the aggregation index obtained in each study site (n=32). The circle diameter is proportional to the spatial aggregation.