Effect of the nematode-trapping fungus Duddingtonia flagrans on the free-living stages of horse parasitic nematodes: a pilot study.

This study examines the ability of a specific fungus, Duddingtonia flagrans, to limit the spread of harmful nematodes, a type of worm, in horses by disrupting their life cycle in horse droppings. Strongyle larvae, another type of parasitic worm, were the specific target in this experiment.

Experimental Method

• Three groups of horses, naturally infected with large and small strongyles, were provided with different amounts of D. flagrans spores as part of their diet at three separate times during the summer of 1995.
• A fourth group of horses acted as a control group and were not fed any of the D. flagrans spores.
• The horses’ feces were regularly emptied onto a parasite-free pasture and were referred to as artificial dung pats in the experiment.
• Every two weeks for a period of 8 weeks, samples from the grass around each of the dung pats were collected and the number of larvae in the grass was counted.

Findings

• The study found that a significant number of D. flagrans spores were able to survive their journey through the horses’ digestive system.
• The presence of these spores in the horses’ feces lowered the incidence of developing larvae, suggesting the fungus had a beneficial effect in controlling the parasitic nematodes’ population.
• However, two factors influenced this reduction of larvae: different batches of the fungus resulted in variances in the level of larval reductions and weather conditions (particularly periods of dry weather) had an effect on the spread of larvae.
• Interestingly, there was no direct correlation between the quantity of fungal spores and the level of reduction in larvae numbers caused by the fungus. This can be interpreted as meaning that merely the presence of the fungus, and not necessarily its quantity, has an impact on controlling the larvae population.
• During the periods of rain, however, a significant reduction was observed in the spread of larvae from the dung pats containing fungal spores.

Implications

• The findings from this pilot study suggest that feeding horses the D. flagrans fungus spores could be a viable method to control parasitic nematode populations in pastures, thereby improving the health of the animals by potentially reducing their worm burden.
• Further research will be necessary, particularly to determine the optimal level of fungus to administer, as the study found no link between the amount of fungus and the reduction of larvae.