Dung-derived biological agents associated with reduced numbers of infective larvae of equine strongyles in faecal cultures.

Two sets of dung-derived organisms from soil routinely fertilized with manure (MA) and soil chemically fertilized (CH) were cultured separately in the laboratory. Baermannized organisms from these cultures were added to 20 g of faeces from strongyle-infected horses to form three treatment groups: (i) no soil organisms; (ii) low inoculum of soil organisms containing all organisms present in a suspension of approximately 100 adult female free-living nematodes; and (iii) high inoculum containing those soil organisms present with approximately 1000 adult female free-living nematodes. Three studies were conducted using MA cultures and faeces containing 50 stronglye epg, CH cultures and faeces containing 1500 strongyle epg, and a mixture of soil organisms from the two cultures (MC) and faeces containing 600 strongyle epg. Within each study, five control cultures and 15 each of low and high inoculum cultures were prepared and incubated at 24 degrees C and 95% humidity in a climate chamber for 15 days. Parasitic and free-living nematodes were then recovered by the Baermann technique and counted. The numbers of third stage larvae were significantly lower in the high inoculum group compared to controls. The percent reductions in the number of third stage larvae for the low and high inoculum groups were 63.6% and 90.9%, 85.1% and 97.1%, 84.5% and 98.4% for MA, CH, and MC studies, respectively, indicating that mortality increased with the number of soil organisms added to cultures. Examination of the source cultures detected the presence of two species of nematophagous fungi and three genera of free-living nematodes reported to be predacious.