For many farmers, the impact of mycotoxins remains a persistent threat, undermining animal health, crop yields and human wellbeing.
At the 1st Animal Production Society of Uganda conference held at Pope Paul Hotel in Kampala, Dr Ochieng Odede of DSM-Firmenich, South Africa, presented a stark warning to stakeholders in agriculture and animal production: the consequences of mycotoxin contamination are pervasive, yet often overlooked.
Dr Odede illustrated his point with the story of an anonymous poultry farmer, whose chicken stock experienced a sudden decline in egg production. After careful investigation, it was discovered that the feed consumed by the birds was contaminated with mycotoxins.
‘It is a silent killer. Farmers may not notice the immediate effects, but the cumulative impact on productivity, immunity, and overall health can be devastating,’ Dr Odede remarked.
Dr Odede emphasised that mycotoxins arise from a combination of biological, environmental, and human factors. The type of fungus and its strain, alongside the susceptibility of the crop, are key biological drivers. For instance, some strains of Aspergillus produce high levels of aflatoxins under the right conditions. Crops weakened by pests, disease, or physical damage are far more vulnerable.
Environmental conditions amplify the risk. Warm, humid climates, erratic rainfall, droughts, and floods all stress plants, creating a fertile environment for fungal growth. Soil quality, irrigation, and temperature fluctuations also influence contamination. Post-harvest, poorly ventilated or humid storage can allow fungi to thrive, further increasing the mycotoxin load.
Agronomic practices also matter. Inadequate crop rotation, planting susceptible varieties, delayed harvesting, improper drying and careless storage can all contribute. Overreliance on fungicides may inadvertently encourage resistant fungal strains.
“The perfect storm of conditions can lead to widespread contamination,” Dr Odede noted.
Surveys over the past decade show that almost every maize crop tested contained aflatoxins. Wheat and rice were also significantly affected, with 88 per cent of wheat and 79 per cent of rice samples testing positive, while oats were less affected at 14 per cent. Another dangerous toxin, ochratoxin A, is commonly found in coffee, wheat, oats, and various vegetables.
In Uganda, tests revealed 404-420 feeds contaminated, with the highest level reaching 6,568 µg/kg of fumonisin B1 (FB1). In simple terms, feed has had very high levels of fumonisin B1, enough to make livestock sick if they ate it.
Mycotoxins impose a heavy financial burden on farmers. In livestock, contaminated feed reduces growth and productivity, forcing farmers to absorb losses in meat, milk and egg production. Northern Uganda studies indicate that only about 7 per cent of feed samples were free from mycotoxins.
Government reports estimate that Uganda loses at least S$38 million annually in potential export revenue due to contamination, illustrating how mycotoxins threaten both livelihoods and the national economy.
A hidden danger
Dr Odede emphasised that mycotoxins affect the immune systems of livestock in varied ways depending on species, toxin type, and dosage.
In pigs, aflatoxin B1 reduces lymphocyte proliferation in piglets, compromises macrophage and neutrophil function, and deregulates antigen presentation. Trichothecenes such as deoxynivalenol (DON) and T-2 toxin can either suppress or stimulate immune responses, with prolonged exposure reducing secondary immune function. Fumonisins disrupt cytokine balance, induce apoptosis and impair antigen-presenting cell maturation, while ochratoxin A affects cytokine expression. Even zearalenone, primarily known for its effects on fertility, can compromise immune cell viability and antibody production.
Poultry are similarly affected. Early exposure to aflatoxins may initially boost humoral immune responses, but chronic exposure depletes lymphoid organs such as the thymus, spleen, and bursa of Fabricius, suppressing antibody synthesis.
DON and T-2 toxin impair protein synthesis and reduce lymphocyte counts, while fumonisin B1 and ochratoxin A compromise macrophage function and organ development.
Ruminants benefit slightly from the natural detoxification capacity of the rumen, which can degrade some mycotoxins, but aflatoxins remain a concern. Chronic exposure in calves and transition cows can even reduce the effectiveness of vaccines.
Humans face similar risks. Consumption of contaminated foods can lead to liver damage, stunted growth, immune suppression and even cancer. Aflatoxin B1, in particular, is highly carcinogenic, while aflatoxin M1, which appears in milk, poses a significant risk to infants and young children. Ochratoxin A can damage kidneys and suppress immunity and fumonisins can affect multiple organs, including the brain and reproductive system. Repeated exposure, even at low levels, is particularly dangerous for children, pregnant women, and agricultural workers.
Climate change and the rising threat
Climate change is exacerbating the problem. Rising temperatures, increased humidity, and erratic rainfall patterns encourage fungal growth and mycotoxin production. Extreme weather events stress crops, reducing their resistance and increasing susceptibility to fungal infection.
According to European Environment Agency reports, exposure to mycotoxins such as DON is already affecting 14% of European adults at harmful levels, and the risk is projected to rise globally.
‘The fungi producing these toxins are highly sensitive to environmental conditions. When we alter the climate, we inadvertently give them an advantage,’ Dr Odede noted.
Managing the threat
Effective management of mycotoxins requires an integrated approach. Agronomic strategies include crop rotation, breeding resistant varieties, careful irrigation, timely harvesting and proper drying.
Physical techniques such as heat treatment, irradiation and careful sorting can reduce contamination, although cost and efficiency remain challenges. Chemical treatments can control fungi but may pose regulatory or safety concerns, while biological control using atoxigenic fungal strains or beneficial microbes offers a promising environmentally friendly solution.
Dr Odede stressed that no single method is sufficient.
“Prevention starts in the field but must continue through storage, processing, and animal feed management,” he said.
Regulatory frameworks, monitoring and awareness among farmers are equally crucial.
Managing mycotoxins
A combination of strategies is often necessary to tackle mycotoxins effectively. Agronomic methods, such as genetic crop improvements and environmentally friendly seed treatments, help prevent contamination in the field.
Physical techniques like sorting, heat treatment, irradiation, and the use of adsorbents can reduce toxin levels in stored crops and feed.
Chemical approaches, including specific fungicides and antioxidants, can also mitigate contamination, although their use is increasingly restricted due to safety concerns.
Biological control has emerged as a promising, environmentally friendly alternative. Non-toxic strains of fungi can outcompete harmful ones, while beneficial bacteria and yeast can inhibit mycotoxin-producing fungi. Enzymes that break down toxins in the digestive systems of animals are also showing potential.
Mycotoxins exemplify the interconnectedness of plant, animal and human health. Protecting crops safeguards animals and ultimately people.
Dr Odede emphasised that tackling these toxins requires a holistic ‘One Health’ approach, combining plant protection, veterinary care, food safety and environmental stewardship.
‘From healthy crops to safe food, the steps we take on the farm ripple across the entire food chain. Preventing mycotoxin contamination is not just a matter of agriculture-it’s about protecting the health of our communities and future generations,’ he said.