Fungus seen as answer to worm threat

A fungus that slowly crushes parasitic worms to death has been found in New Zealand sheep by Lincoln University researchers.

The discovery offers a simple biological control for parasites which threaten the long-term viability of New Zealand's $2 billion-a-year sheep exports.

Resistance to worm drenches is estimated to be present on 63 per cent of sheep farms, including 7 per cent of farms which have multiple resistance to more than one of the three drench "families."

Scientists have for many years urged that farmers cut their use of drenches to a minimum and that they alternate the types of drenches used, so that parasites that survived one type might be knocked out by another.

No new chemicals are available to combat simultaneous resistance to all three of the available drench families.

The fungus discovery means that it could be used to combat drench-resistant worms and slow the increase of resistance.

A research technician in the university's animal and food sciences division, David Wright, examined more than 1700 samples of faeces taken straight from sheep and found six containing the fungus, Duddingtonia flagrans.

These were from sheep in Invercargill, Canterbury and Hawkes Bay.

Team leader of the research group Dr Mike Noonan said the discovery in different areas meant the best strains for New Zealand conditions could be selected.

The fungus kills the worms of the gastro-intestinal nematode parasite on the pasture outside the animal's body, when strands of the fungus encircle the microscopic worm.

"The nematode pokes its head in and the thing clamps around it and tightens," Dr Noonan said.

The fungus has a persistent spore stage which passes through the animal and gets deposited with the faeces, to germinate and attack the worm larvae before they climb the grass sward ready to infect the animal.

Large quantities of spores could be bred and fed to sheep to clean up pastures and prevent reinfection.

Dr Noonan said Mr Wright had collected samples from saleyards in addition to samples sent in by farmers.

"David's got the glamour job. He gets faeces from the back of the sheep before it hits the ground."

Commercial development of a product based on the fungus will be paid by Ancare, a New Zealand-owned animal health company, and Technology New Zealand.

At the moment the team is growing the fungus on sterilised wheat to try to produce sufficient spores.

Lincoln University immunologist and parasitologist Dr Miroslaw Stankiewicz said 90 per cent of parasites were actually on pasture, but most research so far had been oriented to what was in sheep.

"It's very, very simple, and hopefully it will not be expensive," said Dr Stankiewicz.

"It has great potential, and it's green."

- NZPA