Detection and management of aflatoxin contamination in Kenyan smallholder maize
Detection and Management of Aflatoxin Contamination in Kenyan Smallholder Maize Vincent Were1, Samuel Mutiga2, Jagger Harvey1, Vivian Hoffman3, Rebecca Nelson2, Michael Milgroom2. 1Biosciences eastern and central Africa Hub, International Livestock Research Institute, Nairobi, Kenya; 2Dept. of Plant Pathology and Plant-Microbe Biology, Cornell University, USA; 3Maryland Population Research Center, University of Maryland, USA Introduction Expected Outputs Aflatoxins are potent toxins and carcinogens found in the human and livestock food supply. They are produced primarily by the fungal -Build aflatoxin diagnostics capacity at the Hub, for use by African and genus Aspergillus, a pre‐ and postharvest pest. These toxins other partners. continue to be a major health problem in the developing world, where -Develop novel, higher throughput diagnostics (adapt Near Infrared cases of acute exposure can be fatal. Aflatoxins are particularly Spectroscopy to detect Aspergillus in maize flour). damaging to children’s health, stunting child growth and increasing vulnerability to disease. The scope and dynamics of aflatoxin -Characterize the aflatoxin problem in the smallholder farmer food contamination of food in many parts of sub‐Saharan Africa have yet supply. to be clearly characterized. The BecA Hub is involved in a -Limit aflatoxin accumulation and exposure through identification of proper collaborative effort to characterize the scope of the aflatoxin problem crop management and storage conditions. in Kenya, develop new techniques for higher throughput diagnostics and identify existing farmer practices that may help reduce aflatoxin accumulation in smallholder maize. Aflatoxin levels in smallholder maize Maize in Kenya: a staple crop for people and a livestock feed moldy maize grains posho mill (smallholder Ugali 90 Number of samples in each Aflatoxin (ppb) bracket maize flour production) 80 Aflatoxin levels by area 50 45 70 40 60 Aflatoxin 35 Frequency (%) (ppb) 30 50 25 40 20 15 30 10 5 20 0 10 Negatives Below 10 10 to 20 Above 20 Aflatoxin (ppb) 0 Bungoma Eldoret Kisii Kitale Machakos Makueni Nairobi livestock feed milk Conclusion: Maize samples from many areas were positive for aflatoxins, even in a year in which aflatoxicosis was not a recognized problem (May-June 2009). Mycelium sclerotia kernels Cobs Debris http://www.aspergillusflavus.org/aflavus Grain scoring Posho mill users visually sort out moldy and damaged grains. We are investigating whether sorting reduces aflatoxin levels in maize meals, BecA Hub: and if so, identifying which kernel characteristics can be used for Sample collection and analysis sample analysis effective sorting. The kernel integrity; moldiness, discolor, rot (MDR); and kernel texture was measured and correlated with aflatoxin levels. Data analysis is in progress. High MDR score Low MDR score dent flint Aflatoxin extraction Potential Management Strategies •Biological control – using atoxigenic Aspergillus which grows faster than Helica MycoMonitor Total Aflatoxin Assay, a toxigenic Aspergillus. solid phase direct competitive enzyme •Some maize have genes that help in resistance (e.g, genes that immunoassay with a detection limit of 1 part enhance hardness of grain cover). Breeders can develop more per billion (ppb). already analyzed resistant maize varieties. Vicam aflatest (fluorometer/monoclonal •Get a cheaper, easier and faster way of aflatoxin detection for Analysis in progress antibodybased consumers (e.g., at the posho mills). affinity chromatography; 0.1‐300 ppb aflatoxin measurement) •Reduce pre-harvest crop stress and insect damage, which favor fungal infection. Data analysis •Improve storage conditions.Results Future directionsOf the smallholder maize samples tested to date (by Helica), 35% have •Completing analysis of 2009 and 2010 smallholder maize surveys.tested positive for aflatoxin, 11% above the 10ppb level used by some •Incorporating VICAM and Near Infrared Spectroscopy (NIRS) in aflatoxincountries as a threshold above which grains should not be consumed by analysis.humans, and 3% were above the 20ppb used as the threshold by •Potential development of extension guide for training smallholder farmersKenya. Note that the samples were collected in 2009, a time when to properly dry, store and sort grain.aflatoxicosis was not reported. Analysis of samples from an aflatoxicosis •Engagement of strategic national partners to better ensure impact foryear (2010) are in progress. smallholder farmers in Kenya and beyond.