Wild boar density drives Metastrongylus infection in earthworm

Larvae of Metastrongylus spp. lungworms infect wild boar (Sus scrofa) definitive hosts through earthworms (Lumbricidae). We compared the abundance and Metastrongylus spp. larval infection measures of earthworms between two areas (both in Zselic, Hungary, 2012) characterized by markedly different wild boar population densities. Estimated wild boar density was 0.03 animal/ha in free range area and 1.03 animal/ha in enclosure. The mean abundance of earthworm populations (mostly Allolobophora, Aporrectodea, and Lumbricus spp.) was assessed by analysing 140-140 soil samples. The assesment of Metastrongylus spp. larval infection measures was based on cca 100-100 earthworms derived from the two areas. The abundance of earthworms and their Metastrongylus spp. larval infection measures (prevalence and mean intensity) were significantly lower in the free range than in the enclosure. Furthermore, using a finer scale within the enclosure, we compared wild boar feeding sites (n = 30) to other sites (n = 75). Earthworm populations were significantly more abundant and carried significantly more prevalent and more abundant larval lungworm infections at the former sites. These results suggest that high wild boar density and forage supplementation in enclosures increase both the abundance and the larval Metastrongylus infections of earthworms.