We live in a world of fungus. Some, like antibiotics, yeasts and mushrooms, we benefit from; many others, like athlete’s foot, dry rot and fungus on plants and foods, we don’t.
Climate change and milder conditions are predicted to mean an acceleration in the growth and varieties of fungus in the environment generally, and that will mean much greater threats to health, particularly from food susceptible to carrying mycotoxins (toxic substances produced by fungal moulds). Over the last five decades, it’s been shown that cereals, nuts, spices, dried fruits, coffee, cocoa, fruit juices, grapes and red wine may all contain mycotoxins under warm and humid conditions.
Many mycotoxins are ‘hidden’ and aren’t killed off by heat or other kinds of processing. Aflatoxins, especially aflatoxin B1, can damage DNA and causes liver cancer in humans and animals. A recent report from the World Health Organization warned that mycotoxins in the food chain had been ignored for too long and needed a co-ordinated international response. The most recent serious outbreak reported is of school children in rural Kenya who had consumed mouldy maize. This resulted in about 150 fatalities and up to 500 children being hospitalised because of acute exposure to aflatoxins. Other mycotoxins have a range of health effects including kidney damage, gastrointestinal impacts, reproductive disorders or suppression of the immune system.
“Unlike most pests and viruses, we don’t know what new or even existing funguses are out there in the environment”
Southern Europe, for example, is considered to be a hotspot for climate change, where combined changes of elevated CO2 (a predicted doubling of existing levels), increases in temperature (+2 to +4 ºC) and rainfall/drought extremes will have negative effects on food production. Similar impacts are expected in parts of North and South America, Africa and Asia. A 2012 report by the European Food Safety Authority showed that cereal crops will ripen much earlier in the season in future than currently, highlighting the potential for additional impacts of pests and diseases and increases in the prevalence of mycotoxin contamination. In southern Europe and the Balkans, extremely hot summers have already resulted in changes in the maize cultivation ecosystems, resulting in a switch from contamination to the more serious A flavus and aflatoxin contamination, which exhibits a much higher toxicity, affecting feed quality and posing risks of entry into milk and entire dairy production chains.
Pests and fungal diseases are on the march (at an estimated rate of six kilometre per year from the equator outwards to the poles). Under new milder climate conditions there are risks of mycotoxin contamination increasing in regions which have been relied upon as the ‘bread baskets’ for food production. Increased contamination levels of existing mycotoxins, or emigration of other mycotoxins to new regions where they were not previously prevalent may occur. Our recent studies at Cranfield University suggest that one of the results of the predicted climate change will be that the dangerous aflatoxin B1 will be produced from fungal growth on maize-based substrates or maize grain, with profound implications in terms of mycotoxin contamination of cereals. Potential also exists for new mycotoxins occurring for the first time, and impacts on food sustainability in many regions of the world, with developing countries taking the brunt of the impacts.
There’s also the issue of the effects of the global market, transport times through extended supply chains in different climates. Hygiene is critical during medium and long-term storage and during transport of food and feed commodities. Many food products are ‘hygroscopic’, meaning they can easily absorb water and allow mycotoxigenic moulds to grow, and perhaps increase contamination. Often, only small changes in the conditions for dry goods can result in contamination by mycotoxins above the legislative limits. In 2014 at the EU borders, 35 per cent of rejections of human food or feed for animals were due to mycotoxin contamination levels above what’s allowable for health.
“What’s needed is much more monitoring and data on the international picture, what’s coming, along with the early warning systems needed to make sure we have it covered”
Minimisation strategies have included the use of relatively resistant varieties (where these are available), effective pre-harvest Good Agricultural Practices, timing of application of chemical or biological control treatments for pests/fungal infection, and taking into account the weather conditions. But the problem of mycotoxins varies with season and they are very unpredictable in temperate regions of the world. As a result more integrated approaches are being introduced to combine different types of environmental and crop data – pre-harvest and post-harvest – to try and provide an early warning of the relative risk of specific mycotoxins, to try and minimise contamination. We’re starting a new EU-funded project from March 2016 to help farmers by producing a set of tools to help them identify and deal with mycotoxins.
But the issue continues to be a lack of awareness of the threat – unlike most pests and viruses, we don’t even know what new or even existing funguses are out there in the environment, they’re ever-changing. What’s needed now is much more monitoring and data on the international picture, what’s coming along with the early warning systems in needed to make sure we have it covered.