Role of dung beetle feeding mechanisms in limiting the suitability of species as hosts for the nematode Spirocerca lupi.

Various species of dung beetle serve as intermediate hosts after ingesting the embryonated eggs (11-15 × 30-37 µm) of Spirocerca lupi (Spirurida: Spirocercidae) in dog faeces. The feeding mechanisms of coprophagous dung beetles restrict the size of the food particles they can ingest and hence may determine which species can be efficient vectors for S. lupi. In this study, we aimed to exclude certain dung beetle species as possible hosts of S. lupi based on whether or not they ingested latex beads of known diameters mixed into fresh cattle dung. We found that the majority (11/14) of species tested can potentially serve as intermediate hosts of S. lupi because their mouthparts allow the passage of food particles larger than the minimum size range of the eggs of this parasite.

Prevalence of the dog nematode Spirocerca lupi in populations of its intermediate dung beetle host in the Tshwane (Pretoria) Metropole, South Africa.

Spirocerca lupi (Spirurida: Spirocercidae) is a cosmopolitan parasite, principally of domestic dogs and dung beetles are its main intermediate hosts. In South Africa there has recently been growing concern over the upsurge of reported cases of clinical spirocercosis in dogs, while little is known or understood about the dynamics of the host-parasite associations between dung beetles and this nematode. We determined and compared the prevalence of infection in dung beetles between rural, urban and peri-urban areas of Tshwane (Pretoria) Metropole. Dung beetles were sampled during April and October 2006, at various localities in each of these areas. Localities were selected on the basis of being focal areas of high infection with S. lupi in dogs. Pig, dog and cow dung-baited pitfall traps were used for sampling the beetles. Trap contents were collected 48 h after the traps had been set and only dung beetles were collected from the traps. In total, 453 specimens belonging to 18 species were collected from 63 pitfall traps in all three areas. The numbers of species that were collected varied among the three areas. Dung beetles, irrespective of species (18) and numbers (447), predominantly preferred pig dung. The prevalence of dung beetles infected with the larvae of S. lupivaried considerably in the three areas. In the urban area 13.5% of the dung beetles dissected were infected, while the prevalence of S. lupi in dung beetles in the rural area was 2.3%. All the dung beetles that were infected with this nematode showed a preference for omnivore (pig and dog) dung.