By Mark Andrews

A worm-eating fungus brings new hope in the fight against parasitic gastrointestinal worms.

Anthelmintic resistance is now a widespread and growing problem. It is becoming increasingly clear that we cannot rely on chemicals alone to control gastrointestinal parasites. 

Consequently, alternative worm control strategies are being investigated. One method showing promise is the use of a fungus that attacks the free-living larval stages of parasitic worms and so reduces the number of infective larvae on the pasture. 

Duddingtonia flagrans (D. flagrans) is a nematophagous fungus (from the Greek for “worm eating”). The fungus grows rapidly in fresh feces and its chlamydospores (resistant spores) can survive the passage through the gastrointestinal tract of the horse. These fungal spores have no effect on the animal and only germinate once passed in the feces where they develop into nematode-trapping fungal nets.

Recent work in Australia showed that feeding BioWorma®, a supplement containing the Duddingtonia spores, produced substantial reductions in infective larvae on pasture surrounding feces of treated horses, cattle, and goats.

The placebo-controlled trials were conducted in different seasons and bioclimatic regions of Australia (New South Wales, Queensland).

Feces were collected from worm-infected animals after they had been treated with either the D. flagrans supplement or a placebo. The manure was placed on pasture plots and the researchers monitored the numbers of parasitic larvae on the pasture around the faecal pats over an eight-week period.

They report that a minimum daily dose of 3 x 10⁴ D. flagrans spores/kg bodyweight reduced parasite larvae in the pasture surrounding the feces by 53–99 percent over the eight-week period after treatment in horses, cattle, and goats.

Other work has shown that, unlike some chemical dewormers, the fungus does not harm dung beetles or other organisms found in the feces.

BioWorma® is about to be approved for sale in Australia and New Zealand. It should be available in the United States shortly and in Europe within the next year or two.

For more details see: Field evaluation of Duddingtonia flagrans IAH 1297 for the reduction of worm burden in grazing animals: Pasture larval studies in horses, cattle and goats; Kevin Healey, Chris Lawlor, Malcolm R.Knox, Michael Chambers, Jane Lamb, Peter Groves, Veterinary Parasitology 258 (2018) pages 124-132. 

Printed with permission of Mark Andrews, Equine Science Update.

Photo: Canstock/Virgonira

This article was originally published in Canada’s Equine Guide 2019, the January/February issue of Canadian Horse Journal.