Study: Climate change drives spread of toxic Aspergillus mould

In many parts of Kenya, farmers are accustomed to battling pests, drought, or fluctuating market prices. But a subtler, more insidious threat is spreading—one not as easily spotted. It’s a type of mould known as Aspergillus, and experts warn it is becoming more common due to climate change.

This mould poses a dual threat: it can spoil food and cause serious illness, particularly in people with weakened immune systems. Scientists say rising temperatures and changing weather patterns are creating ideal conditions for its growth and spread into new regions.

A recent University of Manchester study, published in Science Advances, found that Aspergillus fungi are likely to expand their reach as global temperatures rise. Some species, such as Aspergillus flavus, infect crops like maize and groundnuts, producing a toxic substance called aflatoxin. Others, like Aspergillus fumigatus, live in soil and dust and can cause severe lung infections when inhaled.

In Kenya, the dangers of aflatoxin are well documented. In 2004, an outbreak in Makueni and Kitui counties claimed over 100 lives. The cause was poorly stored maize contaminated by mould. The Ministry of Health and the Kenya Agricultural and Livestock Research Organisation (KALRO) continue to monitor the threat, especially in eastern regions.

A 2021 study by Jomo Kenyatta University of Agriculture and Technology (JKUAT) and KALRO found that 22 per cent of cashew nuts from the coastal region were contaminated with aflatoxin-producing mould. These findings raise serious food safety concerns, particularly since affected food often looks and smells normal.

Aflatoxin is especially dangerous because it cannot be removed through cooking. Long-term exposure, even in small amounts, can lead to liver damage, weakened immunity, stunted growth in children, and a higher risk of liver cancer. With maize being a staple in most households, this presents a major public health risk. But the threat extends beyond food.

In hospitals, more patients are being diagnosed with fungal infections caused by Aspergillus fumigatus. People with compromised immunity—such as those recovering from tuberculosis, living with HIV, or undergoing cancer treatment—are especially vulnerable. Spores can be inhaled from dust or air, often undetected.

A 2022 study in The Lancet Microbe found that nearly one in five people who had completed tuberculosis treatment but still had breathing problems were actually suffering from chronic pulmonary aspergillosis. Many were misdiagnosed with recurring TB and given the wrong treatment.

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Left untreated, aspergillosis can be deadly. According to the Global Action Fund for Fungal Infections (GAFFI), the mortality rate in untreated cases can reach 90 per cent. To make matters worse, some strains of Aspergillus are developing resistance to widely used antifungal drugs.

A 2023 study by the Mycology Reference Centre in Manchester, which included samples from East Africa, confirmed that some moulds no longer respond to azole-based antifungal drugs. Experts believe the widespread use of chemical fungicides in farming may be fuelling this resistance by helping fungi adapt and survive.

Climate change is making matters worse. Hotter days, irregular rainfall, and longer dry spells are creating ideal conditions for mould growth. Key crops, such as maize, groundnuts, and cashew nuts, dietary staples for many communities—are especially at risk.

Despite the rising threat, many hospitals in Kenya lack the tools to diagnose fungal infections, and awareness among healthcare workers and the public remains low. This often leads to missed or delayed diagnoses. There are economic consequences too, as contaminated produce destined for export may be rejected, affecting small-scale farmers’ livelihoods.

Several initiatives aim to reduce exposure. Organisations such as the International Institute of Tropical Agriculture (IITA) and the FAO are supporting grain testing and training farmers in safe drying and storage methods. Some counties are already using improved storage bags and exploring natural controls, such as beneficial soil bacteria.

In healthcare, early detection is vital. GAFFI recommends routine screening for fungal infections in TB clinics, especially when patients do not respond to treatment. Doctors need better training to identify fungal illnesses and choose the correct medication.

Nationally, stronger food safety laws and public awareness campaigns are needed, along with integrating fungal threats into climate and health policy. Progress is slowly being made.

In counties like Machakos and Tharaka Nithi, farmers are learning better post-harvest practices, and some hospitals are beginning to monitor fungal infections more closely. But experts warn that these efforts are still too limited. A nationwide, coordinated response is urgently needed.

Aspergillus exists naturally in soil, dust, and sometimes in food. What’s changing is how often it appears—and how dangerous it can become. Climate change is fuelling its spread, but with early intervention, improved farming, and stronger healthcare, this silent threat can still be managed.