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Prevalence of aflatoxin along the maize value chain in kenya
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Prevalence of aflatoxin along the maize value chain in kenya

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  • 1. Prevalence of aflatoxin along the maize value chain in Kenya. George Mahuku (CIMMYT) & Henry (H. Sila) Nzioki (KARI)
  • 2. Mycotoxin producing fungi• Weak parasite• Very susceptible to ecological F. graminierum A. Flavus F. verticillioides conditions• Optimum DON FB AF conditions differ for growth & toxin production• Mycotoxins production Temp 25° 35° 30° elicited by stress aw 0.98 0.78 0.96
  • 3. Mycotoxins in Maize and effect on human healthFungus Mycotoxin International Health Effects limits (vary)Aspergillus Aflatoxin B1 (0 – 50 ppb) Carcinogen, affecting the liver,flavus and A. reduced efficiency of theparasiticus Kenya (10 ppb) immunological system, retards growth and development of childrenFusarium Fumonisin B1 4 ppb Asociated with esophageal cancer,verticillioides and neural tube defects leading to abortionFusarium Zearalenone Not established Properties of estrogen hormonesgraminearumF. Deoxynivalenol 1 ppm Reduced efficiency of thegraminearum immune systemPenicillium Ochratoxin A Not established Chronical renal diseasesverrucosum
  • 4. Variation in acceptable aflatoxin levels
  • 5. Aflatoxin• are naturally occurring mycotoxins produced by the fungi Aspergillus flavus and A. parasiticus.• not all A. flavus strains are toxigenic• grow on maize, peanuts ,wheat, beans and rice.• are a problem particularly in warm and humid, tropical countries.• drought conditions are ideal for growth and proliferation of fungi.
  • 6. Aflatoxin affected major crops• Cereals: Maize, Sorghum, Pearl millet• Oil seeds: Groundnuts, Soybean, Sunflower• Spices: Chillies, Black pepper, Turmeric• Tree nuts: Pistachio, Almonds, coconut
  • 7. Aspergillus and aflatoxin• Aspergillus flavus – opportunistic pathogen• Superior adaptability – Survives in a wide range of environments: soil, plant debris, dead insects and seeds• Fungus does not need a live host to survive• Complex environmental and ecological factors affect A. flavus infection and aflatoxin contamination.• Aflatoxin contamination is: – unavoidable under the present production, processing and storage of crops & commodities.• Infection and aflatoxin contamination can occur at pre-harvest, harvest, post-harvest, process, storages, transit stages
  • 8. Factors affecting Aflatoxin contamination of Maize Environmental Factors Harvesting Biological Factors -Temperature - Crop maturity -Susceptible crop - Moisture availability - Temperature - Compatible toxigenic fungi - Mechanical injury - Moisture -Insect/ bird damage -Handling Processing & Humans Storage Animals -Structure; -Moisture; -Temperature Distribution Detection/diversion Animal Products
  • 9. Aflatoxin in the Food Chain FEED
  • 10. Response to different concentrations of aflatoxinzero Increasing concentration of aflatoxin
  • 11. Objectives• Understand the incidence and prevalence of aflatoxin along the maize value chain in selected study areas.• Identify critical points where intervention technologies are mostly likely to be more effective
  • 12. Maize Sampling Sites• Lower Eastern – Machakos County: Machakos, Kathiani Kangundo and Matungulu Districts – Makueni County: Mbooni East and Makueni Districts• Upper Eastern – Embu County: Mbeere North, Embu North and Embu West Districts• South Western Kenya – Homabay County: Homabay and Rongo Districts – Kisii County: Kisii Central District
  • 13. Methodology• Along identified critical points along the market chains, samples were collected: • Pre-harvest – physiological maturity while in the field • Harvest, handling and processing for storage • Storage by farmers (30 day interval) • Markets (30 day interval) • Assemblers • Wholesalers • Retailers • Consumers of products
  • 14. Information / Data collected• Farmer / Actor name• GPS coordinates• Maize variety• Source of maize• Moisture content• I kg maize sample for analysis (following a standard protocol: Aflacontrol website)
  • 15. Maize samples collected from farmer fields (pre-harvest) YearRegion 2009 2010 2011 TotalLower Eastern (LE) 30 167 143 340Upper Eastern (UE) 10 41 40 91South Western - 153 99 252(Homabay/Rongo [HR})South Western (Kisii - 78 41 119Central [KC])Total 40 439 323 802
  • 16. Maize samples collected from farmer stores (post-harvest / storage) YearRegion 2009 2010 2011 TotalLower Eastern 87 276 156 519Upper Eastern 59 253 44 356South Western - 368 101 469(Homabay/Rongo)South Western (Kisii Central) 30 214 39 283Total 176 1111 340 1627
  • 17. Maize samples collected from markets YearDistrict 2009 2010 2011 TotalLower Eastern 152 535 219 906Upper Eastern 126 232 38 396South Western - 345 92 437(Homabay/Rongo)South Western (Kisii 52 154 40 246Central)Total 330 1266 389 1985Total Samples analyzed = 4,414
  • 18. Maize samples from farmer fields & Stores withaflatoxin levels above and below 10ppb (2009)120 #Samples <10 (μg/kg)100 % Samples >10 (μg/kg)80 Region Range60 (μg/kg) STDev Upper Eastern (UE) 0 - 9091.8 2874.940 FF Lower Eastern (LE) 0 - 273.8 68.920 Upper Eastern (UE) 0 - 27393.7 4188 0 FS UE LE UE LE (N= KC Lower Eastern (LE) 0 - 3180.7 422 (N=10) (N=30) (N=58) 87) (N=30) Kisii Central (KC) 0 - 5.4 1.6 Farmer Fields Farmer Stores
  • 19. Maize samples from market with aflatoxin levels above and below 10ppb (2009)60 % Samples <10 (μg/kg)50 % Samples >10 (μg/kg)4030 Region Range (μg/kg) STDev20 Upper Eastern (UE) 0 - 12000 216010 Lower Eastern (LE) 0 - 9302 166.40 Kisii Central (KC) 0 – 3442.2 2160 KC (N=52) LE (N=152) UE (N=126)
  • 20. Proportion of Maize samples from the farmer stores with aflatoxin levels above 10 ppb (2009) 90 80 70 60 50 1 month PH 40 2 months PH 3 months PH 30 20 10 0 Makueni Embu Mbeere Kisii North
  • 21. Proportion of Maize samples from the market with aflatoxin levels above 10 ppb (2009) 100 90 80 70 60 1 month PH 50 2 months PH 40 3 months PH 30 20 10 0 Makueni Embu Mbeere Kisii North
  • 22. Maize samples from farmer fields & Stores with aflatoxin levels above and below 10ppb (2010)90 % Samples <10 (μg/kg)80 % Samples >10 (μg/kg)706050 Region Range (μg/kg) STDev40 Upper Eastern (UE) 0 - 252 52.730 Lower Eastern (LE)20 0 – 1454.8 139.1 FF10 Hbay/Rongo (HB) 0 – 722.2 660 Kisii Central (KC) 0 – 558.7 77.5 Upper Eastern (UE) 0 – 22641.7 253.5 Farmer Fields Farmer Stores Lower Eastern (LE) 0 – 1978.3 234.5 FS Hbay/Rongo (HB) 0 – 1511.2 123.6 Kisii Central (KC) 0 – 611.8 77.2
  • 23. Maize samples from the first and secondseasons with aflatoxin levels above 10ppb (2010) 50 45 40 35 30 25 October-November 20 March - May 15 10 5 0 Lower Eastern Upper Eastern Hbay/Rongo Kisii Central (N=149) (N=41) (N=153) (N=79)
  • 24. Proportion of samples collected from farmer stores with aflatoxin levels above 10 μg/kg (2010)February – March harvest July - August harvest 8080 707060 6050 KisiiCentral 5040 Homabay / Rongo 4030 Lower Eastern 3020 Upper Eastern 2010 10 0 0 1 month 2 months 3 months 1 month 2 months
  • 25. Maize samples from markets with aflatoxin levels above and below 10ppb, (2010)9080 % Samples <10 (μg/kg)70 % Samples >10 (μg/kg)6050403020 Region Range (μg/kg) STDev Upper Eastern (UE) 0 – 1632.9 184.710 Lower Eastern (LE) 0 – 2076.7 188.40 Lower Upper Hbay/Rongo Kisii Central Hbay/Rongo (HB) 0 – 379.5 42 Eastern Eastern (N=345) (N=154) (N=535) (N=232) Kisii Central (KC) 0 – 1308.8 148.9
  • 26. Maize samples from farmer fields & Stores with aflatoxin levels above and below 10ppb (Jan – May 2011)120 % samples < 10ppb100 % samples >10 ppb80 Region Range (μg/kg) STDev Upper Eastern (UE)60 0 – 581.5 94.4 Lower Eastern (LE) 0 – 354.6 49.840 FF Hbay/Rongo (HB) 0 – 20.2 3.620 Kisii Central (KC) 0 – 63.1 9.8 0 Upper Eastern (UE) 0 – 248.5 49.1 Lower Eastern (LE) 0 – 685.6 92.9 FS Hbay/Rongo (HB) 0 – 41.6 5.6 Farmer Fields Farmer Stores Kisii Central (KC) 0 – 357.2 57
  • 27. Maize samples from markets with aflatoxin levels above and below 10ppb, (Jan – May, 2011)10090 % samples < 10ppb80 % samples >10 ppb70605040 Region Range30 (μg/kg) STDev20 Upper Eastern (UE) 0 – 1679.6 286.210 Lower Eastern (LE) 0 – 3568.3 335.9 0 Hbay/Rongo (HB) H/R (N=92) KC (N=40) LE (N=219) UE (N=38) 0 – 36.8 5.9 Kisii Central (KC) 0 – 60.7 9.7
  • 28. Conclusion• 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.• We did not find differences in aflatoxin levels among varieties / hybrids grown by farmers.• Contamination starts from the field – Need to factor in environmental conditions• Aflatoxin is not homogeneously distributed in contaminated lots. Sampling poses a major challenge, hence the fluctuations between sampling times.• Aflatoxin contaminated maize samples were found from both South western and Eastern Kenya regions• This is the first systematic study looking at aflatoxin contamination along the maize value chain
  • 29. Acknowledgements• Partners: Ministry of Agriculture extension staff, Farmers, Traders, KARI – Katumani staff: Centre Director, crop protection and support staff• ICRISAT for aflatoxin analysis• ACDI/VOCA• Financial support – Bill and Melinda Gates Foundation