1: Vet Parasitol. 1997 Nov;72(3-4):479-85; discussion 485-92.Click here to read Links
Biological control of gastro-intestinal nematodes--facts, future, or fiction?
Larsen M, Nansen P, Grønvold J, Wolstrup J, Henriksen SA.
Danish Centre for Experimental Parasitology, Department of Veterinary Microbiology, Royal Veterinary and Agricultural University, Frederiksberg, Denmark.
mila@kvl.dk The potential of using fungi to prevent nematodosis caused by parasites with free-living larval stages is well documented today. In this respect Duddingtonia flagrans, a net-trapping, nematode-destroying fungus, appears to be the most promising candidate. Laboratory experiments and in-vivo studies, where fungal spores have survived passage through the gastro-intestinal tract of cattle and horses, plus field studies with cattle, horses and pigs, demonstrate significant reduction in the number of infective larvae that develop in the faecal environment.
In field trials this reduction subsequently leads to reduced infectivity of herbage and also reduced worm burdens in grazing animals. A status of the present situation, primarily based upon work performed in Denmark within the last 6-8 years, plus an outlook for practical implementation of an integrated control strategy including the use of nematode-destroying fungi in the future is discussed.
PMID: 9460213 [PubMed - indexed for MEDLINE]
1: Vet Parasitol. 1993 Jun;48(1-4):311-25.
In Denmark two series of experiments have been performed to study the interactions between larvae of bovine gastrointestinal nematode parasites and nematode-trapping fungi. For practical reasons we were interested in the possibility of depositing nematode-trapping fungi in cattle faeces after passage through the gastrointestinal tract. In the first series, laboratory tests with the fungus Arthrobotrys oligospora showed that motile free-living larvae of a wide range of animal-parasitic nematodes and some soil-living nematodes effectively induce the formation of traps. Larvae of all parasitic nematodes are rapidly captured in these traps. The induction of nets was influenced by temperature, number of larvae, atmosphere, light, and media composition. Captured first- and second-stage larvae were quickly penetrated and killed while third stage larvae were killed slowly, perhaps because they are partially protected by an outer dead sheath. Laboratory and field studies showed that when A. oligospora material was directly mixed into dung a significant reduction in the number of infective parasite larvae in the dung and surrounding herbage occurs. This reduction was also reflected in the acquired worm burden of calves grazing on fungal treated pasture.
However, the A. oligospora strain studied in the above mentioned experiments did not survive passage through the alimentary tract of cattle. This prompted us to start a second series of experiments to isolate fungi that could survive gut passage of cattle. Different soil and. compost samples were screened by an in vitro stress selection technique. This simulated certain important stress factors which occur during passage through the alimentary tract of ruminants. Rumen exposure was found to be a major limiting factor, but some Arthrobotrys and Duddingtonia strains survived submersion in rumen fluid.
In a subsequent in vivo experiment, some of these survivors were fed to calves, and it was hereby demonstrated that isolates of both genera, i.e. Arthrobotrys and Duddingtonia, were able to survive passage through calves and significantly reduce the number of developing preparasitic larvae in dung of fungal treated calves. In a controlled field experiment, isolates of Duddingtonia reduced the level of infective third-stage larvae in herbage by 74-85%.
PMID: 8346645 [PubMed - indexed for MEDLINE]