Biological control using fungi could provide an effective option for tackling the problem of parasitic gastrointestinal nematodes in livestock.
That’s the view of Yunnan University scientists behind a review of evidence on their experimental use to date, who say that their use alone and in combination with other options could help overcome the problem of resistance to anti-parasitic drugs.
In Europe alone, parasitic worms cost the livestock industry €1.8billion a year, with €38million a result of drug resistance.
95% of gastrointestinal nematodes are found outside the bodies of animals, they noted, meaning that efficacious approaches to tackling the free-living life stages of the parasites are needed. Currently, anti-parasitic drugs are used to attack adults inside the animals, whereas a novel approach such as fungi could be applied to the animal faeces to kill both eggs and juveniles.
Research highlights promising candidates
A number of nematode-consuming fungi have been tested in studies, the reviewers reported. These include predatory fungi from the genera Arthrobotrys, Drechsleralla, and Dactylellina, as well as Duddingtonia flagrans, which has the quality of producing numerous spores and uses a network structure to capture juvenile nematodes living in faeces.
Arthrobotrys is another promising fungal genus, the scientists wrote, with large reductions reported in the larvae of some nematode species after it has been applied, while Pochonia is seen as a promising genus for killing female and egg stages of the parasites.
Only a fraction of known fungal species are able to kill nematodes, and the effectiveness of such fungi depends on the species used, and also local environmental conditions. To reduce uncertainty in the selection of possible candidate fungi for the biocontrol in specific areas, species could be isolated from livestock faeces, the researchers suggested.
Fungi to form part of broader strategy?
Studies have also shown that combining groups of fungal species can have greater effect than using one alone — while work has also suggested that good efficacy is possible when biocontrol is combined with the conventional control approach of drugs.
“Although resistance is quickly developed to chemical drugs, they are more effective at killing nematodes than fungi, so the combination of the two could also reduce resistance and enhance nematicidal efficiency,” they concluded.
“Further studies are still needed to establish the pattern of combining NF with chemical drugs, such as the compatibility, appropriate dose, and time.”
