Food safety scientists launch a report about the level of food contamination, in particular aflatoxin, in the food chain in Uganda. PHOTO/LOMINDA AFEDRARU
Consumption of aflatoxin-contaminated food can severely impact human fertility, experts warn. Prof Samuel Majalija, the director of research at the National Agricultural Livestock Resources Research Institute (NaLIRRI), reveals that men who consume maize and other staples contaminated with high levels of aflatoxins risk reduced sperm count, while women may experience disrupted egg production, both contributing to infertility.
“Aflatoxins interfere with sperm development in men and egg development in women, significantly affecting fertility,” Prof Majalija stated.
He urged schools to regularly test food items, especially maize, beans, chicken, and beef for aflatoxins and other harmful microbes.
“Our schools need to be vigilant. They should test food every term before serving it to students. We have found that most of the beef and maize consumed in schools contain dangerously high levels of aflatoxins and microbes that can also cause cancer,” Prof Majalija revealed.
He further warned that groundnut paste, a staple in many households in central and northern Uganda, may also be highly contaminated.
Aflatoxins are naturally occurring toxins produced by fungi that infect crops like maize and groundnuts. They are known to cause liver cancer, childhood stunting, immune suppression, and substantial trade losses.
Linda Agnes Auma, the chairperson of the Parliamentary Committee on Agriculture, Animal Industries and Fisheries, echoed these concerns. Her committee’s report to Parliament highlights a troubling rise in liver cancer cases in northern Uganda, directly tied to prolonged consumption of aflatoxin-laced food.
“The findings are alarming,” Auma said.
“Without swift government action, we risk losing many lives,” Auma warned.
Contaminated maize sold locally
Bogere, a maize farmer and middleman, has admitted to selling aflatoxin-contaminated maize locally after it was rejected by international markets.
“We had collected maize for export, but it was rejected in Kenya due to contamination levels of 30 parts per billion (PPB). We sold it domestically to avoid losses,” said Bogere.
Widespread food safety challenges
Food safety is a growing public health and economic concern in Uganda, with more than 1.3 million people affected by food-borne diseases annually.
Aflatoxins are especially dangerous because they resist cooking, accumulate in animal products, and can even be found in breast milk. In collaboration with international bodies such as the Food and Agriculture Organisation (FAO) and local partners like Consent Uganda, scientists at the National Agricultural Research Organisation (Naro) are deploying advanced technologies to reduce food contamination from production through to consumption.
Report findings on aflatoxins
A report by Food Safety Coalition Uganda outlines how Uganda's food system is vulnerable to biological (fungi, bacteria), chemical (pesticide residues), and physical contaminants (pests, foreign objects). Regulatory enforcement and public awareness are limited, and traditional food handling practices contribute to the problem.
Key contributors to the report include Prof Archileo Kaaya (Makerere University), Henry Richard Kimera (Consent Uganda), and Aggrey Atuhaire (FAO). They describe aflatoxins as highly carcinogenic and stable toxins that thrive in humid storage conditions, causing long-term health issues such as liver cancer and digestive complications.
Uganda spends approximately $910,000 annually on aflatoxin-related health services and could lose up to $577 million per year due to trade restrictions and productivity losses.
Ongoing interventions
Uganda has launched various initiatives to tackle food safety, including policy frameworks, stakeholder coalitions, and awareness campaigns. However, enforcement remains weak, innovation underfunded, and technical capacity limited. Poor post-harvest handling and counterfeit agrochemicals also hinder progress.
Recommendations from experts
Regulatory enforcement: Strengthen monitoring of aflatoxins and other contaminants. Infrastructure investment: Improve drying, storage, and food handling technologies.
Capacity building: Train farmers, traders, and regulators on safe food practices. Public awareness: Launch nationwide education campaigns about aflatoxin risks and prevention.
Expert perspectives
Dr Moses Matovu (Naro) noted aflatoxin levels as high as 35 PPB in maize—far exceeding the 10 PPB safety limit—cost Uganda over Shs180 billion in rejected exports. He called for better-equipped testing labs across the country.
Prof Majalija cautioned against feeding contaminated food to livestock and criticised reliance on visual inspections in abattoirs. He emphasised the need for proper withdrawal periods after antibiotic and acaricide use to prevent chemical residues in meat and milk.
Prof Kaaya added that even small, repeated consumption of aflatoxins can lead to cumulative health damage and eventual death. He urged farmers to improve post-harvest practices proper drying, clean storage, and moisture control.
Innovation and technology
Naro scientists have introduced several innovations:
Aflasafe: A biocontrol product applied during planting and crop growth to reduce aflatoxin production.
Mobile apps: Tools providing education to farmers and value chain actors. Fish smoking kilns: Designed to reduce harmful polycyclic aromatic hydrocarbons in smoked fish. Antibiotic test kits: Tools to detect residues in milk.
Anti-tick vaccine: A solution to reduce acaricide overuse in livestock. One health approach: Measures to prevent zoonotic disease transmission between animals and humans.
Advice to farmers
Farmers are urged not to slaughter or milk animals recently treated with antibiotics or acaricides due to health risks. The advised withdrawal period is at least two weeks. Prof Majalija emphasised the importance of proper testing procedures.
While visual inspections are common in abattoirs, more advanced lab testing is necessary to detect contamination effectively. He stated that NaLIRRI has labs capable of identifying the nine known aflatoxin strains—four of which are particularly dangerous to human and animal health.
Factors promoting aflatoxin contamination of grains Aflatoxin contamination of foods and feeds highly depends on biological (biotic) and environmental (abiotic) factors that lead to mould growth and toxin production and can occur both pre-and post-harvest.
For example, mechanical damage, insect and bird damage, drought, stress and excessive rainfall encourage pre-harvest mould growth and aflatoxin production. Strain variation in the fungus, interference by other micro- organisms, moisture, temperature, pH, the gaseous environment and preservatives are also important factors.
In addition, the incidence and levels of fungal infection and aflatoxin contamination reported vary markedly from one geographical area to another. In most instances, however, aflatoxins are formed after harvest, particularly when harvesting takes place during floods, or unseasonal rains or when there is improper storage of insufficiently dried agricultural commodities.
The following factors have been singled out as those that mainly encourage mould growth and aflatoxin production in grains and kernels:
Moisture content
The amount of moisture in a grain affects both grade and storability and has a critical effect on mould growth and mycotoxin production. It is one of the most important considerations in determining whether aflatoxin will develop in groundnuts after harvest.
Storage fungi grow at moisture contents in equilibrium with relative humidities ranging from 65-70 to 85-90 percent. A. flavus will only grow when the moisture content exceeds 9 percent, at 80-85 percent relative humidity and above.
Soil moisture stress has also been reported to enhance pre-harvest aflatoxin contamination of produce. Groundnuts exposed to drought stress in the field have been reported to have more A. flavus infected kernels than in irrigated plots.
Excessive drought causes strains on pods and testas thus providing entry points for infection by fungi while excessive moisture weakens the pods and testas causing the same effect.
Temperature
The effect of temperature is difficult to separate from the effect of moisture. Under favourable temperature and relative humidity conditions, aflatoxigenic fungi grow on certain foodstuffs, most commonly grain like cereals and nuts. Production of aflatoxins is optimal at relatively high temperatures, so contamination is most acute and widespread in warm, humid climates.
Under tropical conditions typical of Uganda, stored products are more susceptible to aspergillus species than other fungi, as many aspergilli are favoured by the combination of low water activity and relatively high storage temperatures.
Aspergillus flavus grows best between 10oC and 45oC at a relative humidity of 75 percent or more although the optimum conditions for aflatoxin production are between 25oC and 30oC, at 85 percent relative humidity.
Handling and drying
Mechanical damage to kernels makes them much more vulnerable to invasion by storage moulds, including A. flavus.
Under any given environmental conditions fungal growth is several times faster in damaged compared to intact kernels.
Cracks and breaks in grains are caused mainly during harvesting and shelling, although insect and rodent feeding may also be responsible for breaks in the pericarp.
Traditional groundnut drying techniques in developing countries like Uganda involving field and bare ground drying are a major source of fungal contamination. They are slow, time consuming and labour intensive involving lots of crop handling (that the resource-limited farmer may not adequately accomplish), and due to rains that normally persist at harvesting and drying times, it is difficult to achieve the recommended moisture level for safe storage.
In addition, the crop is persistently exposed to soil contamination which is the source of fungi.
Management
Storage conditions
The fundamental reason why commodities are stored dry is to increase storability and in part, prevent growth of storage fungi. If commodities are incorrectly stored, that is, in an improperly dried state or under high humidity with inadequate protection, fungi will inevitably grow.
Duration of storage is an important factor when considering mycotoxin formation. The longer the retention in storage the greater will be the possibility of building up environmental conditions conducive to aflatoxigenic mould proliferation in groundnuts.
Storage structures commonly used by farmers in Uganda are traditional and may not maintain an even, cool and dry internal atmosphere; they do not provide adequate protection from insects and rodents; are not easy to clean and above all, are not water proof. All these conditions favour mould growth and aflatoxin production.
Insect infestation or damage
Insect infestation during storage is one of the major problems facing farmers in Uganda. Insects and mites may damage stored grain, but they also interact with fungal colonisation in many different ways. Fungal spores can be carried by insects.
Toxin-producing fungi can infect growing crops, as a consequence of insect damage and may produce toxins prior to harvest or during harvesting and storage.
During storage, insects, due to their metabolic heat and water, can increase the water activity and temperature of grain to levels suitable for fungal growth. Thus, it is important that insects are controlled both pre and postharvest.
Economic effects of aflatoxins
Aflatoxins in all crops, can have direct economic effects resulting in loss of produce or loss of market value as well as indirect economic effects from loss of animals, increased costs of veterinary and human health care services, costs for food-borne disease surveillance and food monitoring.
Presence of high levels of aflatoxins in groundnuts may make it unacceptable for marketing, causing financial loss to the farmer or retailer.
Depending on the market, economic losses may reach 100 percent, when the entire produce/product is rejected by the market if aflatoxin levels are higher than acceptable standards.
It is estimated that Africa loses more than $670 million annually due to requirements for European Union aflatoxin standards for all food exports and world over, billions of dollars are lost by farmers and traders due to aflatoxin contamination.
It is therefore, very essential that all parties involved in the process of producing and marketing groundnuts and other crops should ensure that contamination from mycotoxins is minimised as much as possible. Additional reporting by Dr David Kalule Okello
