The fate of helminth eggs and protozoan cysts in human feces ingested by dung beetles (Coleoptera: Scarabeidae)

The digestive tracts and excrement of dung beetles were examined after ingestion of human feces containing the eggs of hookworm, Ascaris, and whipworm, and cysts of Entamoeba coli, Endolimax, and Giardia. Practically no eggs and few cysts were recovered from Canthon laevis and C. vigilans, and no Ascaris larvae were found in the former after the ingestion of embryonated eggs. From Phanaeus vindex and Ph. igneus unaltered whipworm eggs and more cysts, but no hookworm and few Ascaris eggs, were recovered. Only Pinotus carolinus, the largest species, regularly contained and excreted ingested eggs. Recovered Ascaris eggs were decorticated and sometimes crushed, but many from the gut of Pinotus proved viable when incubated. Destruction of eggs and cysts is attributed to the grinding action of the beetles' mandibles, which is evidently least efficient in Pinotus. Although dung beetles may be significant in other ways in the dissemination of hookworm, the species most abundantly attracted to human stools destroy ingested eggs of this parasite and of Ascaris and do not transport them internally.