Field experiment on the ability of earthworms (Lumbricidae) to reduce the transmission of infective larvae of Cooperia oncophora (Trichostrongylidae) from cow pats to grass

In Denmark earthworms play an important role in the disappearance of cow pats on pastures. Field investigations were designed to study the influence of earthworms on the transmission of infective Cooperia oncophora larvae from experimental cow pats to grass. Results from the present experiment showed that cow pats, protected from attack by earthworms, disappeared at a much lower rate than unprotected cow pats. Development in faeces and transmission to grass of C. oncophora larvae were disturbed by the disintegration of cow pats. The rapid disintegration of unprotected cow pats resulted in an approximately 50% reduction of infective C. oncophora larvae on grass in the vicinity of these cow pats, as compared with larval contamination of grass around protected cow pats. How earthworms may cause a reduction in the transmission of infective C. oncophora larvae to grass by creating adverse conditions for the survival of parasite larvae in the cow pats, by eating and killing the parasite larvae, and by depositing parasite larvae in the soil is discussed.