Opinion piece by AgResearch chief scientist Axel Heiser:

Facial Eczema (FE) in cattle and sheep represents a long-standing challenge for New Zealand's agricultural sector, undermining the health and productivity of livestock while imposing significant economic and emotional burdens on farmers.

The recent announcement(external link) of an $8.3 million commitment by the Ministry for Primary Industries through the Sustainable Food and Fibre Futures Fund, alongside a $9 million contribution from Beef + Lamb New Zealand and additional funding from other industry partners  –  totalling $20.75 million over a seven-year period – marks a pivotal moment in the fight against this disease.

This collective effort, encapsulated in the Eliminating Facial Eczema Impacts (EFEI) programme, promises to address the critical knowledge gaps and management challenges that have hampered progress for over a century.

FE, caused by the toxin-producing fungus Pseudopithomyces chartarum, leads to liver damage, reduced animal productivity, and severe animal welfare issues. Traditionally, management strategies have included the application of fungicides and zinc supplementation, methods that are not sustainable due to environmental and health concerns.

While selective breeding for resistance presents a promising avenue, it requires a long-term commitment to realise its potential as a viable solution. The economic toll of FE on the New Zealand agricultural sector is profound, with estimated impacts reaching $332 million annually due to reduced livestock growth rates and stock losses during severe outbreaks.

The knowledge gaps surrounding FE are profound and multifaceted. This is a critical barrier to the development of strategies to address the problem. Despite decades of concerted research efforts, our understanding of FE remains fragmented, particularly in areas critical for its control and eventual eradication.

AgResearch chief scientist Axel Heiser

The challenge of detecting the fungus Pseudopithomyces chartarum in pasture is one of these critical knowledge gaps in our fight against FE. The accurate measurement of spore counts in pasture, a crucial indicator of FE risk, is fraught with difficulties.
Current methodologies may not accurately reflect the true risk of FE to livestock because not all spores contain the toxin sporidesmin, which is responsible for the disease. This discrepancy means that even with high spore counts, the actual risk of toxicity could be over or underestimated, depending on the proportion of spores carrying sporidesmin.

This issue complicates the development of risk management strategies for farmers, who rely on spore counts as a key metric for deciding when to implement disease mitigation practices such as moving animals to safer pastures or beginning zinc treatment protocols. The variability in sporidesmin presence within spore populations necessitates a more nuanced approach to measuring FE risk, one that goes beyond simple spore counts to assess the actual toxic potential of pastures.

Understanding the factors that influence sporidesmin production by Pseudopithomyces chartarum, including environmental conditions, fungal genetics, and interactions with the host plant, is essential for developing more accurate predictors of FE risk.
Research into these areas could lead to the development of diagnostic tools that not only count spores but also measure the concentration of sporidesmin or identify spore variants more likely to produce the toxin. Such tools would represent a significant advancement in FE management, providing farmers with the information needed to make informed decisions about protecting their livestock from this debilitating disease.

The need for more effective diagnostic tools stands as a primary concern. Current approaches often fail to detect the disease in its early stages, particularly when animals are asymptomatic or presenting signs that are not easily recognised, leading to underestimations of prevalence and severity.

Knowledge gaps on Facial Eczema in livestock need to be filled, before solutions are found

Another significant knowledge void is our depth of understanding of genetic resistance against FE.

While there is awareness that some genetic lines in livestock exhibit greater resilience to the disease, the specific genetic markers associated with resistance are not well defined. This hinders the ability to put in place targeted breeding programmes that could mitigate the impact of FE over the long term.
The complexity of genetic interactions with environmental factors further complicates this issue. It suggests that resistance may not be solely determined by single mutations in the genes but rather by a complex interplay of multiple genetic and environmental factors.

We also know that sustainable management practices for FE are inadequately developed. The reliance on fungicides and zinc, while providing some level of disease control, raises concerns about environmental sustainability, animal health, and the potential for resistance development. These methods do not address the root causes of FE or offer long-term solutions.
Sustainable practices that could prevent the conditions conducive to the growth of the fungus, Pseudopithomyces chartarum, or reduce the exposure of animals to toxic spores are poorly understood and under-researched.
The interactions between the fungus, the host (livestock), and the environment also represent a substantial area of incomplete knowledge. Factors such as climate change, farming practices, and landscape alterations are likely to influence the epidemiology of FE, yet how these factors affect one another and can be managed for FE prevention remains unclear.
Furthermore, the potential for other disease-causing organisms to contribute to, or exacerbate, the FE disease complex has not been thoroughly investigated. This leaves open the question of whether we are addressing all aspects of what causes the disease and its spread.

Bridging these knowledge gaps requires a commitment across different areas of expertise that encompasses advanced research into genetics, diagnostic development, epidemiology, environmental science, and sustainable agricultural practices.

The EFEI programme represents a holistic and ambitious effort by government, industry and scientists to not just manage but eliminate the impacts of FE. Addressing the knowledge and management gaps, the programme focuses on several key areas: improving diagnosis of the disease, understanding its genetic basis, and exploring new management strategies.
The economic, environmental, and social benefits of the EFEI programme are far-reaching. Economically, the programme promises to reduce the annual cost of FE to the agricultural sector by developing more effective management tools and practices. Environmentally, it seeks to reduce the reliance on zinc and fungicides, which have adverse effects on soil and water quality. Socially, the programme has the potential to significantly improve farmer well-being by reducing the stress and emotional burden associated with managing FE.

All of this gives me cause for optimism that together we may finally be able to turn the tide on this costly and debilitating livestock disease.

**This piece was previously published in an abbreviated form on the Stuff website**

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