[Limitation in the population of parasitic geohelminths by saprotrophic soil fungi and their secretions].

INTRODUCTION

The aim of the study was to examine the effect of mould fungi isolated from soil and of two of their metabolites, aflatoxin G1 and ochratoxin A, on the embryonic development of eggs and mortality of larvae of Ascaris suum. An attempt was made to demonstrate synergism between fungi species in the action on embryogenesis of Ascaris suum.

MATERIAL AND METHODS

Fungi were isolated from soil and cultured on the standard Czapek-Dox agar medium at 26 degrees C for 60 days. Fertilized eggs of Ascaris suum were incubated in PBS solution with the mycelium of each species or without fungi in the control culture. To demonstrate synergism between fungi species, eggs were cultured with three combinations of two species. Additional cultures were done with aflatoxin G1 and ochratoxin A at concentrations of 0.5, 1, and 2 ppm.

RESULTS

Microscopy showed a slower rate of development of eggs from experimental cultures as compared to the control culture. Fungi, as well as mycotoxins, caused vacuolization of the zygote, uneven division of blastomeres, and morphological abnormalities of the embryo. The highest mortality (36%) of invasive larvae of Ascaris suum was caused by Paecylomyces fumosoroseus. The present study revealed that the antagonistic effect of a fungi on the development of Ascaris suum eggs is increased or decreased in the presence of another fungi species. Exposure to aflatoxin G1 and ochratoxin A at concentrations as low as 0.5 ppm leads to a greater percentage of deformed embryos and 100% mortality of larvae.