New Fungus Discovery Marks Major Breakthrough In Battle Against Facial Eczema In Sheep

New Zealand scientists have made a significant breakthrough in understanding a complex fungal disease that severely affects sheep, revealing the existence of a previously unidentified fungal species.

Facial eczema, a serious condition in livestock, is caused by a toxin produced by a fungus that thrives in warm and humid conditions. This toxin damages the liver of sheep, making them highly sensitive to ultraviolet light and severely impacting their health and productivity. The disease costs New Zealand farmers and the broader economy an estimated $332 million annually.

Until now, it was believed that only one fungal species was responsible. However, new research has uncovered the presence of two distinct species in New Zealand pastures. Scientists have now identified the second, newly discovered species as Pseudopithomyces toxicarius, which has been confirmed as the main producer of sporidesmin—the toxin behind facial eczema. This is in addition to the well-known but non-toxic Pseudopithomyces chartarum.

Dr. Bevan Weir, senior scientist at Manaaki Whenua Landcare Research and lead author of the study, explained that the team conducted extensive research on fungal organisms, their genomes, and the toxins they produce, both locally and internationally.

“We were amazed when we received the initial DNA sequencing results. The data showed a remarkably clear genetic split that confirmed the existence of two separate species in the pasture,” Weir said.

He described the moment of discovery as incredibly rewarding, especially given prior confusion over varying toxicity levels in fungal strains. The breakthrough now explains earlier observations of both toxic and non-toxic strains.

The discovery follows years of dedicated work by researchers, agricultural scientists, and farmers. The research effort included collaboration between AgResearch, Manaaki Whenua, Beef + Lamb New Zealand, and the Livestock Improvement Corporation. The initiative, led by Beef + Lamb, is part of a seven-year, $20.75 million project aimed at eliminating the impact of facial eczema in livestock. In March last year, the New Zealand government contributed $8.3 million to support the program.

Weir emphasized that identifying the true cause of facial eczema marks a “critical step forward” in mitigating its damage.

“What makes this so challenging is that although these two species are genetically very different, they look completely identical under a microscope—even high-powered research microscopes can’t distinguish between them,” he explained.

This similarity poses a problem for veterinarians and farmers who currently assess facial eczema risk by counting fungal spores. Since both toxic and non-toxic species appear the same under a microscope, the current method may misrepresent the actual risk level.

To address this, researchers are continuing to collect sheep fecal samples from across the country. This ongoing work will help pinpoint where each fungal species is most commonly found. Early findings suggest that toxic strains are much more prevalent in the North Island than in the South Island.

AgResearch’s lead researcher, Christine Voisey, acknowledged the valuable contributions made by farmers who provided crucial samples for the study.

“This has been one of the most fulfilling projects of my career,” Voisey said. “While we still have more to learn about the biology of Pseudopithomyces, this research brings us closer to developing practical tools that can reduce the burden of facial eczema on New Zealand’s farming community.”

Dan Brier, General Manager of Farming Excellence at Beef + Lamb New Zealand, added that the research provides a much clearer scientific basis for creating better diagnostic tools and effective farm management practices to combat the disease.

“This knowledge sets a solid foundation for more accurate assessment of facial eczema risk and allows us to create more targeted strategies to protect our livestock,” Brier said.

The breakthrough offers hope for reducing the devastating effects of facial eczema and boosting the resilience of New Zealand’s agricultural sector.

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