Feeding a natural fungus to sheep, cattle and goats can provide an effective alternative to chemical drenches to control worm parasites by means of biological control. Rather than trying to cure round worm infestations with drugs, the aim is to break the worm life cycle by preventing livestock ingesting infective larvae when grazing.
Finally, there is a commercial product that will do just that. BioWorma® and Livamol® with BioWorma® will be available from mid-July 2018 for use in Australian livestock.
Australian strains of the nematode-destroying fungus, Duddingtonia flagrans, were first discovered in a CSIRO survey of grazing properties during the early 1990s. When fed to livestock, the fungal spores pass through the gut of the animal and are excreted with the worm eggs in the dung. The fungal spores then germinate and grow networks of traps that ensnare and kill the worm larvae soon after they emerge from the eggs. The adult worms living in the animals do not live forever, so this cycle of constant re-infection is required to maintain the worm infestation in the sheep.
Even though the fungus is fed to livestock, the product does not kill the worms inside the stock, it targets the larvae as they emerge from eggs in the dung. Feeding the product to livestock is the means to get the fungus into the faeces.
Placebo controlled studies were conducted according to Good Clinical Practice standards by an independent contractor, in which the animals were fed the fungal spores dispersed in a nutritional supplement (placebo). The trials were undertaken in different seasons and climatic regions. Modelling by CSIRO and the Danish Centre for Experimental Parasitology showed that the levels of control obtained in these trials greatly reduce the effects of parasites on the animals (Barnes et al.,1995).
These typically took place over a 4-month period and the supplement containing the fungus was fed on a group basis, rather than individual feeding. They demonstrated an average reduction of about 70% (P<0.05) in worm burdens in the tracer lambs that were used to measure the infectivity of the pasture (Healey, Lawlor et al., 2018a). A summary of the results is shown in the Figure below (worm burdens in the tracers at the end of each trial).
In these trials, efficacy was measured by direct counting of infective larvae on pasture surrounding faecal pats obtained from control and BioWorma-treated cattle over an 8-week period. Typical results are shown below. Over all four trials the reduction in larval numbers due to treatment averaged 81% (P<0.01) (Healey, Lawlor et al., 2018b).
These trials were conducted in the same manner as the cattle trials, with an average reduction in larval numbers of 86 % (P=0.01) over six trials (Healey, Lawlor et al., 2018b). Typical results are shown below.
The main parasites encountered in the Australian sheep, cattle and goat trials included Barber's Pole worms (Haemonchus spp.), Black Scour Worms (Trichostrongylus spp.), Brown Stomach Worms (Teladorsagia spp.), Small intestinal Worms (Cooperia spp.), Thin-necked Intestinal Worms (Nematodirus spp.) and Nodule Worms (Oesophagostomum spp.). This included numerous multi-resistant strains.
Long term safety studies were conducted in sheep and cattle with the fungus fed at 5–10 times the dose over a 6–8 week period with no harm detected. Also, a suite of safety studies were conducted in laboratory animals, which showed the fungus is not infective or toxic, meaning it is safe for farmers to handle.
Laboratory studies by expert chemists showed that any residues produced by the fungus were below the appropriate European Union Safety guidelines. Further, investigation by specialist toxicologists showed freedom from undesirable characteristics such as genotoxicity.
The fungus is easy to use by means of daily administration in a nutritional supplement or in feed rations. For best results, firstly perform a worm egg count and, if appropriate, animals should be treated with an effective chemical drench and then the fungus is fed to maintain a low-worm status.
Ideally, when commencing feeding the fungus, the animals would also be moved onto pasture that had been rested to allow its burden of infective worm larvae to die off (see WormBoss recommendations on times required in different regions). Alternatively, a paddock that has been cross-grazed with another species of animal can be used. However, it is important to bear in mind the process of refugia management (see WormBoss guidelines for more about this) and to remember that the fungus will not affect worm larvae that have already emerged on the pasture.
CSIRO researchers also investigated the possible adverse effects of D. flagrans on beneficial soil organisms in a typical improved pasture (Knox et al., 2002). The presence of fungi in livestock faeces did not affect the abundance of beneficial soil nematodes and microarthropods. There were also no negative effects of fungal presence on the numbers of other nematode-trapping fungi. Over time, there was generally a decline in the presence of the fungi and the rate of decline appeared to depend on seasonal conditions. Drier conditions appeared to prolong the presence of the fungi in faecal matter.
Numerous other studies around the world have shown similar results and have demonstrated absence of impact on dung beetles and earthworms.
The APVMA (Australia), MPI (New Zealand) and US EPA have granted registration of two products containing a CSIRO isolate of D. flagrans (IAH 1297) for control of gastrointestinal nematodes in grazing animal animals, namely BioWorma® and Livamol® with BioWorma®. These products are made by Australian-owned company, International Animal Health Products Pty Ltd, who began their collaboration with CSIRO in 1997. Registration is pending in the EU.
There are two Bioworma® products that suit different end-users.
Healey, Lawlor et al., 2018a. Field evaluation of Duddingtonia flagrans IAH 1297 for the reduction of worm burden in grazing animals: Tracer studies in sheep, Vet. Parasitol. 253, 48-54. https://doi.org/10.1016/j.vetpar.2018.02.010 (Open Access).
Healey, Lawlor et al., 2018b. Field evaluation of Duddingtonia flagrans IAH 1297 for the reduction of worm burden in grazing animals: Pasture larval studies in horses cattle and goats, Vet. Parasitol. 258, 124-132. https://doi.org/10.1016/j.vetpar.2018.06.017 (Open Access).