The ability of the biological control agent Duddingtonia flagrans to reduce the availability of livestock parasites on pasture

Silvina Fernández (Guelph, ON)
The following is an adaptation of a scientific article published in the Journal of Helminthology, Volume 73, Issue 2, 1999, pages 115-122

The nematode-trapping fungus Duddingtonia flagrans has been studied for a while because of its potential role as a biological control agent in the fight against gastrointestinal parasites (internal round worms) of livestock. The fungus traps and kills the parasite larvae present in the animal feces, which then reduces the number of infective larvae (L3) migrating later on to the pasture, thus lowering the risk of parasitic infection in animals.

In this study, the ability of two isolates of D. flagrans to reduce the numbers of gastrointestinal parasite larvae on herbage was tested in three experimental trials.

Cattle feces contaminated with parasite eggs, and with and without the addition of D. flagrans, were used to make fecal cultures kept in the laboratory, and also to form fecal pats which were deposited on pasture plots two or three times during three consecutive grazing seasons.

Grass samples from around each pat were taken fortnightly over a period of 2 months and the number of parasite larvae was recorded. At the end of the 2 month period, the remainder of the fecal pats were collected to determine their wet weight, dry weight, and content of organic matter, and to extract the remaining L3 as well.

The results from fecal cultures showed that both fungal isolates significantly reduced the number of L3 by 62 to 98%. On the pasture, significantly fewer larvae were recovered from grass surrounding fecal pats, containing the fungus compared with control pats (without fungus) in all three experiments, reflecting the ability of the fungus to destroy the parasite larval stages in the fecal pat environment. One fungal isolate reduced the number of L3 on pasture by 76 to 85%, while reduction caused by the second fungal isolate was 62 to 98%.

After 2 months on pasture, there were no differences between control fecal pats and fecal pats with fungus with respect to their wet weight, dry weight, and organic matter content. This indicates that the natural degradation of feces was not negatively affected by the presence of the fungus.


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