Ovicidal action of a crude enzymatic extract of the fungus Pochonia chlamydosporia against cyathostomin eggs

The aims of this study were to test the action of the fungal extract of Pochonia chlamydosporia (VC4) on the hatching of cyathostomin eggs plated in Petri dishes containing 2% water-agar (2% WA) and its enzymatic activity in fecal cultures, in two experimental assays (A and B). The fungus P. chlamydosporia (VC4) was cultured in Erlenmeyer flasks (250 ml) containing 50 ml of liquid minimal medium supplemented with 0.2% gelatin for production of the crude enzymatic extract. Approximately 1 kg of fresh feces was collected directly from the rectum of crossbred horses naturally infected with cyathostomins. The fecal material was used to obtain eggs and prepare fecal cultures. For assay A, one thousand eggs were plated on 4.5 cm diameter Petri dishes together with 5 ml of VC4 fungal filtrate and incubated at 26 °C in the dark for 24 h. The control group consisted of 1000 eggs in Petri dishes containing 10 ml of distilled water, which were incubated under the same conditions. After 24 h, the total number of cyathostomin larvae present in each plate of the treated and control groups was counted. For assay B, about 20 g of feces were added with 10 ml of fungal extract of P. chlamydosporia (VC4) and incubated at 26 °C for 8 days. Third stage larvae (L3) were recovered at the end of this period. Significant difference (p < 0.01) was found for the number of larvae between the treated group and the control at end of assay A. A 72.8% reduction in the hatching of cyathostomin eggs was found in the plates of the treated group compared with the control group. At the end of 8 days, the fungal extract of P. chlamydosporia (VC4), in assay B, was effective in reducing the number of L3 cyathostomins in the treated group by 67.0% compared with the control group. Significant difference (p < 0.01) was found between the means of L3 recovered from the treated group and the control group. The results of this work showed that crude enzymatic extract of P. chlamydosporia (VC4) was effective in reducing hatching of cyathostomin eggs and therefore could be used as a biological control agent of this nematode.