The use of Duddingtonia flagrans as a tool for the biological control of gastrointestinal nematodes (GIN) is a promising alternative to anthelmintics. The chlamydospores of D. flagrans are orally dosed and their thick cell wall gives them the capacity to resist digestion and pass through the gastrointestinal tract (GIT). Chlamydospores reaching the faeces are able to germinate and trap nematode larvae. The efficacy of this control method is based on reducing the numbers of infective larvae leaving the faeces. Techniques have recently been developed for quantifying the numbers of chlamydospores in faeces. As the number of non-digested spores could be relevant in the design and optimization of dosing programmes for the control of GIN infective larvae, the aim of the present study was to estimate the loss of D. flagrans chlamydospores during their passage through the ruminant gastrointestinal tract using in vitro and in vivo techniques. After in vitro rumen digestion, chlamydospore recovery was not different from the quantity originally incubated (undigested spores) (P > 0.05). In vitro rumen+abomasum digestion caused nearly 36% loss of the chlamydospores originally incubated (P < 0.05). Germination of chlamydospores classified as viable was 24.3%. Chlamydospores classified as non-viable did not germinate. Rumen digestion resulted in more spore germination (R1 = 35.7% and R2 = 53.3%) compared to no digestion (time 0 h = 8.7%). Subsequent abomasal digestion reduced germination (R1+A = 25%) or stopped it (R2+A = 0%). In vivo apparent chlamydospore digestibility in sheep showed a loss of 89.7% of the chlamydospores (P < 0.05). The loss of chlamydospores was evident under in vitro and in vivo conditions. Negligible amounts of spores were lost during the in vitro rumen digestion. However, in vitro rumen+abomasum digestion resulted in a chlamydospore loss of approximately 36%. In vivo passage through the sheep GIT resulted in a total loss of 89.7% of the orally administered spores.

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Digestibility of Duddingtonia flagrans chlamydospores in ruminants: in vitro and in vivo studies

Assessing the efficacy of Duddingtonia flagrans chlamydospores per gram of faeces to control Haemonchus contortus larvae.

A technique for the quantification of Duddingtonia flagrans chlamydospores in sheep faeces

Improved method for Duddingtonia flagrans chlamydospores production for livestock use.

Effect of Paecilomyces lilacinus on the viability of oncospheres of Taenia hydatigena.

The fungus, Duddingtonia flagrans, is able to trap and kill free-living nematode larvae of the cattle parasite Cooperia oncophora when chlamydospores are mixed in cattle faeces Isolates of Bacillus subtilis (two isolates), Pseudomonas spp (three isolates) and single isolates of the fungal genera Alternaria, Cladosporium, Fusarium, Trichoderma and Verticillium were isolated from cattle faeces and shown to reduce D flagrans growth on agar plates When these isolates were added to cattle faeces containing D flagrans and nematode larvae of C oncophora, developing from eggs, none of the isolates reduced nematode mortality attributed to D flagrans Similarly, the coprophilic fungus Pilobolus kleinii, which cannot be cultivated on agar, also failed to suppress the ability of D flagrans to trap and kill developing larvae of C oncophora Increasing chlamydospore doses of D flagrans in faecal cultures resulted in higher nematode mortality Thus, no evidence of interspecific or intraspecific competition was observed The consequences of these findings are discussed

Interspecific competition between the nematode-trapping fungus, Duddingtonia flagrans, and selected microorganisms and the effect of spore concentration on the efficacy of nematode trapping.

A. Gillespie

Papers

Interspecific competition between the nematode-trapping fungus, Duddingtonia flagrans, and selected microorganisms and the effect of spore concentration on the efficacy of nematode trapping.