Biological control with nematophagous fungi as alternative pathways for nematodes control in goats : efficacy, impact of a treatment by thiabendazole

The high prevalence of benzimidazole resistance of nematodes in French grazing goats flocks leads to define nematode-control schemes based on integrated approaches with non-chemical options like biological control. The effect of the daily feeding of the nematophagous fungi Duddingtonia flagrans to goats on the third stage larvae (D) of Trichostrongylus colubriformis and Teladorsagia circumcincta and on the survival of the first stage larvae (L1) of Muellerius capillaris was examined in faeces culture. On the other hand, the effect of a benzimidazole treatment with thiabendazole on D. flagrans was tested. Reductions in development of digestive nematodes larvae in fungi groups compared to control groups were more than 80 % at the dose rate of 5 * 10(5) spores/kg body weight per day. On the contrary, there was no difference on the survival of M capillaris L1 between the 2 groups receiving or not the fungi. Thiabendazole exerts a high fungicidal effect on D. flagrans in vitro but no effect was seen in an in vivo assay because of the inhibition of the larval development of T. colubriformis by thiabendazole.