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Preliminary results showing prevalance of aflatoxin in maize in Kenya by George Mahuku (CIMMYT) and Sila Nzioki (KARI)


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Presentation from the Aflacontrol Conference on Aflatoxins, Food Safety and Food Security, Nairobi, Kenya January 2011

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Preliminary results showing prevalance of aflatoxin in maize in Kenya by George Mahuku (CIMMYT) and Sila Nzioki (KARI)

  1. 1. Prevalence of aflatoxin along the maize value chain in Kenya – preliminary findings. <br />George Mahuku (CIMMYT) & Henry <br />(H. Sila) Nzioki (KARI)<br />
  2. 2. Mycotoxin producing fungi<br />Weak parasite<br />Very susceptible to ecological conditions<br />Opt conditions differ for growth & toxin production<br />Mycotoxins production elicited by stress<br />F. graminierum<br />F. verticillioides<br />A. Flavus<br />FB<br />DON<br />AF<br />Temp<br />25°<br />30°<br />35°<br />aw<br />0.98<br />0.96<br />0.78<br />
  3. 3. Mycotoxins in Maize and effect on human health<br />
  4. 4. Aflatoxin<br />are naturally occurring mycotoxins produced by the fungi Aspergillus flavus and A. parasiticus.<br />not all A. flavus strains are toxigenic<br />grow on maize, peanuts ,wheat, beans and rice. <br />are a problem particularly in warm and humid, tropical countries.<br />drought conditions are ideal for growth and proliferation of fungi.<br />
  5. 5. Aspergillus and aflatoxin<br />Aspergillusflavus– opportunistic pathogen<br />Superior adaptability<br />Survives in a wide range of environments: plant debris, dead insects and especially seeds<br />Fungus does not need a live host to survive<br />Complex environmental and ecological factors affect A. flavusinfectionand aflatoxin contamination.<br />Aflatoxin contamination is:<br /> unavoidable under the present production, processing and storage of crops & commodities. <br />Infection and aflatoxin contamination can occur at pre-harvest, harvest, post-harvest, process, storages, transit stages<br />
  6. 6. Factors affecting Aflatoxin contamination of Maize<br />Environmental Factors<br />-Temperature<br />- Moisture<br />- Mechanical injury<br />-Insect/ bird damage<br />Harvesting<br />- Crop maturity<br />- Temperature<br />- Moisture<br /> -Handling<br />Biological Factors<br />-Susceptible crop<br />- Compatible toxigenic fungi<br />Storage<br />-Structure; <br />-Moisture; -Temperature<br />Humans<br />Animals<br />Distribution & Processing<br />Detection/diversion<br />Animal Products<br />
  7. 7. Good Agricultural Practices<br />Handling & processing<br />Storage<br />Cropping <br />Systems<br />Harvesting<br />
  8. 8. Aflatoxin affected major crops<br />Cereals: Maize, Sorghum, Pearl millet<br />Oil seeds: Peanuts, soybean, sunflower<br />Spices: Chillies, Black pepper, Turmeric<br />Tree nuts: Pistachio, Almonds, coconut<br />
  9. 9. Aflatoxin contamination<br />Affects<br /> Crops, Commodities, food and feed,<br /> Human and livestock health<br /> International trade & economic impacts<br />
  10. 10. Aflatoxin in the Food Chain<br />FEED<br />
  11. 11. Objectives<br />Understand the incidence and prevalence of aflatoxin along the maize value chain in selected study areas.<br />Identify critical points where intervention technologies are mostly likely to be more effective<br />
  12. 12. Maize Sampling Sites<br />
  13. 13. Background image is Bio01 from WorldClim<br />
  14. 14. Methodology<br /><ul><li>Along identified critical points along the market chains, samples will be collected at different intervals in time:
  15. 15. Pre-harvest
  16. 16. Harvest, handling and processing for storage
  17. 17. Storage method (15 to 30 days interval)
  18. 18. Markets (every month)
  19. 19. Assemblers
  20. 20. Wholesalers
  21. 21. Retailers
  22. 22. Consumers of products</li></li></ul><li>Pre-harvest Sampling<br /><ul><li>In a plot, 5 squares will be identified inside which 5 samples were drawn.
  23. 23. The samples of each square were shelled, mixed and a 1 kg sample drawn.</li></li></ul><li>Post-Harvest sampling from farmer stores and bags<br />Samples collected from three levels (top, middle and bottom<br />Thoroughly ,mixed, and a 1 kg sample randomly drawn.<br />Top<br />Middle<br />Bottom<br />
  24. 24. Information / Data collected<br />Maize variety<br />Source of maize<br />Moisture content<br />GPS coordinates<br />
  25. 25. 2009 <br />Sampling<br />Pre-harvest<br />Ph: 15-25<br />FS: 30-40<br />FS: 60-70<br />
  26. 26. 60-70<br />30-40<br />90-100<br />
  27. 27. 30-40<br />60-70<br />Mbeere North<br />Mbeere North<br />90-100<br />Most maize not from Original stock,<br /> but sourced from market<br />Mbeere North<br />
  28. 28. 60-70<br />30-40<br />
  29. 29. Proportion of Maize samples from the farmer stores aflatoxin levels above 10 ppb (2009)<br />
  30. 30. Proportion of Maize samples from the market with aflatoxin levels above 10 ppb (2009)<br />
  31. 31. Percent of maize samples from farmer fields with aflatoxin levels above and below 10ppb, (Jan – Feb 2010)<br />
  32. 32. Percent of maize samples from farmer stores with aflatoxin levels above and below 10ppb, 1 month post harvest (April-May 2010)<br />
  33. 33. Percent of maize samples from markets with aflatoxin levels above and below 10ppb, (April-May 2010)<br />
  34. 34. Conclusion<br />Occurrence of aflatoxins in maize is a complex series of interaction between G x E x Pathogen x Farmers practices. This complexity poses difficulties in achieving control. <br />Contamination occurs under field conditions<br />Need to factor in environmental conditions <br />Poor awareness of the problem, lack of human capacity and infrastructure for aflatoxin monitoring are major bottlenecks.<br />Training in good agricultural practices.<br />Drying is a major bottleneck, especially after the short rains – need for mobile drying systems.<br />Aflatoxin is not homogeneously distributed in contaminated lots. Sampling posses a major challenge, hence the fluctuations between sampling times<br />