New map series to warn of aflatoxin risks

26 March 2019

APHLIS is producing a series of maps that provide early warning information on climate-based risks of aflatoxin contamination, a major threat to plant, animal and human health

A powerful poison

The map shows — for each province — the percentage of periods prior to harvest (over the years from 2004 to 2018), that crops were likely to be subject to aflatoxin risk due to heavy rainfall. (Image: APHLIS) 

Aflatoxins are poisons produced by moulds – mainly Aspergillus flavus and A. parasiticus – that normally occur in tropical and subtropical countries where temperatures and humidity are high. The moulds can contaminate food crops before they are harvested, especially if the crops have been weakened by drought. Contamination can also take place postharvest due to improper drying, storage or transport. And if grains are exposed to high levels of humidity in the harvest period or during postharvest operations, moulds will develop and can produce toxins that may reach much higher levels than in the field. Insect or rodent infestations may also facilitate the contamination of some stored commodities. Cereal and nut crops are particularly vulnerable to infestation.

Aflatoxins are powerful carcinogens and exposure poses serious threats to both human and animal health. They are known to cause liver cancer in humans and have been linked to other forms of cancer and to birth defects and stunting in children. Large doses of aflatoxins lead to acute poisoning (aflatoxicosis) that can be life threatening. Chronic exposure to aflatoxins from food is believed to affect 4.5 billion people in developing countries.

Aflatoxins also pose serious risks to farm animals that ingest infected feed. The effects on chickens include liver damage, diminished egg production and reproductive efficiency, and increased susceptibility to disease. Cattle suffer from weight loss, liver and kidney damage, reduced milk production, and blindness. Animal deaths and reduced productivity from aflatoxin exposure can have significant negative economic impacts, in addition to the harmful health outcomes for people who consume contaminated animal products.

An estimated 25% of the world’s food crops are significantly affected by aflatoxin infestation. Without serious intervention, that figure will surely grow: climate change is bound to have a wildfire effect on the spread of aflatoxins if temperatures continue to increase in cool and temperate climates and rains continue to become more erratic, making it difficult for farmers to properly time their harvest and postharvest operations.

Mapping aflatoxin risk

Effective farm and pest management systems can reduce aflatoxin contamination. These include timely planting, maintaining optimal plant densities, proper plant nutrition, avoiding drought stress, controlling other plant pathogens, weeds and insect pests and proper harvest and postharvest operations. Knowing where the risks exist enables policymakers and extension workers to promote and support such systems where they are needed the most.

ASAP (Anomaly Hotspots of Agricultural Production) is an early warning system that monitors drought stress and excessive rainfall to help avert food crises and facilitate response planning. Developed by the by the Joint Research Centre (JRC) of the European Commission, ASAP gathers information that can be used to predict possible pre-harvest contamination by aflatoxins, which flourish under conditions of drought and excess water. ASAP provides automatic warnings every ten days about rainfall anomalies and low vegetation performance at the provincial level. The automatic warnings are verified by agricultural analysts to enable the identification of countries with potentially at risk agricultural production conditions.

With support from JRC, APHLIS is using ASAP data to map climate-based pre-harvest aflatoxin risks at the provincial level across sub-Saharan Africa. The maps enable analysts and decision-makers to pinpoint areas at risk in every season, guiding contamination detection and the implementation of mitigation measures. The maps are based on international research results on aflatoxin infestation of cereal crops, and focus on two highly vulnerable moments in the agricultural production cycle: grain-filling and the period immediately before and after harvest. The maps provide warnings around both drought stress and high rainfall.

Drought stress warning

During the period of grain-filling, plants are highly responsive to aflatoxins. If drought occurs during this period, aflatoxins are likely to follow. APHLIS will provide warnings every ten days when a remote sensing-derived biophysical indicator, the NDVI (Normalized Difference Vegetation Index) is smaller than 86% of all previous years (starting in 2004) during maturation (the period between maximum vegetation activity and 75% of the season length, which generally includes grain filling).

High rainfall warning

APHLIS is also concerned with the period immediately before and after harvest, when overly humid conditions can put crops at risk. We will provide a warning when the Standardized Precipitation Index (SPI) during plant senescence (the period falling between 75% and 100% of the season length) is larger than 86% of the previous years since 1989 (n.b. the data time series available for the reference period is longer than for the biophysical indicator).

Based on ASAP data, APHLIS has calculated historical aflatoxins risk maps – dating back 15 years – for drought during crop growth and exceptional rainfall around the time of harvest. We are currently sharing the maps with postharvest and aflatoxins experts for validation. Once validated, the maps will be available to aflatoxins experts and our network of country experts in order to verify the consistency of their data with historical aflatoxin occurrence. The APHLIS team will present the aflatoxins risk mapping approach at the 3rd MycoKey Technological Workshop, which will be held in Zurich, Switzerland from 18 to 19 June 2019.

A few of the references used to develop the model can be found below:

Battilani, P., & Leggieri, M. C. (2014). Predictive modelling of aflatoxin contamination to support maize chain management. World Mycotoxin Journal.

Chauhan, Y. S., Wright, G. C., & Rachaputi, N. C. (2008). Modelling climatic risks of aflatoxin contamination in maize. Australian Journal of Experimental Agriculture, 48(3), 358.

Rembold, F., Meroni, M., Urbano, F., Csak, G., Kerdiles, H., Perez-hoyos, A., … Negre, T. (2019). ASAP: A new global early warning system to detect anomaly hot spots of agricultural production for food security analysis. Agricultural Systems, 168(May 2018), 247–257.

For further information, please contact:

Dr Felix Rembold
Joint Research Council, European Commission


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