Biological Control of Helminth Parasites by Predatory Fungi

Abstract

Biological control of animal parasites could  become a strong arm for Integrated Parasite  Control in the very near future. Though various  nematode-destroying fungi received attention,  predominantly on academic interest, from the  18th Century in Scandinavian countries, work on  their application to control animal parasites  gathered momentum from 1990's. The philosophy  behind biological control is to utilise one or more  of the natural enemies of the nematodes, making it  possible to reduce the infection on pasture to a  level where grazing animals can avoid both  clinical and subclinical effects of the parasitic  nematodes. The important requirement is the  presence of the fungi in the faecal pats where the  development of the pre-parasitic larvae takes  place. Therefore, to be effective, the fungi should  pass through the gastrointestinal tract of the host  without loss of viability. The fungi, Duddingtonia  flagrans and Verticillium chlamydosporium,  which can be isolated from organic environment  of India produces thick walled chlamydospores,  the stage responsible for their survival during  passage through the gut of ruminants following  oral administration. The results had indicated  survival of the fungus during gastrointestinal  transit in grazing animals and successful  reduction of numbers of parasitic nematode  larvae on pasture. The dose of fungal spores to be  given to an animal and the time of administration  for effective parasite control has been  standardised. The fungus behaves in density  dependent manner and appears to be  environment-friendly. The challenge lies ahead in  its field application.