Viability of the nematophagous fungus Pochonia chlamydosporia after passage through the gastrointestinal tract of horses

Abstract

The predatory capacity of the nematophagous fungus Pochonia chlamydosporia (isolate VC4) embedded in sodium alginate pellets after passage through the gastrointestinal tract of horses was assessed in vitro against Oxyuris equi eggs. Twelve previously dewormed crossbred mares, average weight of 362.5 kg (±21) were used in the experiment. Each animal of the treated group received an oral dose (100 g) of sodium alginate pellets containing P. chlamydosporia mycelial mass. The control group received pellets without fungus. Faecal samples from fungus-treated and control groups were collected at intervals of 8, 12, 24, 36, 48 and 72 h after pellet administration and placed in Petri dishes containing 2% water-agar. One thousand eggs of O. equi were plated in Petri dishes of both treated and control groups, with six replicates, and incubated in oven, 25 °C, in the dark, for 30 days. At the end of the experiment, one hundred eggs were removed from each Petri dish and classified according to the following parameters: type 1, physiological and biochemical effect without morphological damage to eggshell, with hyphae adhered to the shell; type 2, lytic effect with morphological change in the eggshell and embryo without hyphal penetration, and type 3, lytic effect with morphological change in the eggshell and embryo, with hyphal penetration and internal egg colonization. Chlamydospore production was observed in Petri dishes of the treated group. The isolate VC4 remained viable after passing through the gastrointestinal tract of horses and maintained the ovicidal activity against O. equi eggs when compared with the control group (p < 0.01) after each collection interval: 29.1% (8 h), 28.2% (12 h), 31.1% (24 h), 27.4% (36 h), 30.9% (48 h) and 28.4% (72 h). The results suggest that P. chlamydosporia could be used as an effective biological control agent of O. equi eggs in natural conditions.