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Aflatoxins in Grains and Food Safety, Guantai, S.M., ACDI/VOCA Kenya

Aflatoxins in Grains and Food Safety, Guantai, S.M., ACDI/VOCA Kenya



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

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



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  • This was really a nice presentation, congratulations and thanks. I find it very helpful in my project. Apart from the contaminated weaning flour in Kisumu..... Are there any other specific examples of reported cases of aflatoxin poisoning in the Lake Victoria Basin?
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    Aflatoxins in Grains and Food Safety, Guantai, S.M., ACDI/VOCA Kenya Aflatoxins in Grains and Food Safety, Guantai, S.M., ACDI/VOCA Kenya Presentation Transcript

    • Aflacontrol conference Southern Sun Hotel, 13 th January 2011 Aflatoxins in Grains and Food Safety Guantai S.M. ACDI/VOCA Kenya 02/15/11
    • Introduction
      • What are mycotoxins
      • Occurrence and Hazards of mycotoxins
      • Epidemiological association in Kenya
      • Factors that lead to fungal growth and Aflatoxins formation
      • Toxins of aspergillus spps
      • Hazard critical control points
      • Aflatoxins contaminated grains
      • Incidences of Aflatoxins Poisoning
    • What are Mycotoxins
      • Naturally occurring toxic metabolites of fungi produced in minute quantities (ppb).
      • The name is derived from two Greek words:- mykes for fungus or mould and toksikon ( latin toxicum) for toxin (poison)
      • There are 500 different types of toxins produced naturally by 150 species of fungi. Of these 200 are known to occur in the food value chain.
      • Most important mycotoxins are produced by fungi of the genera:
      • Aspergillus
      • Penicillium
      • Fusarium
      • Cleviceps
    • Occurrence and Hazards
      • Aflatoxins are the most severe of the mycotoxins and contamination affects over 25% of global food and feed.
      • Contamination occur in the field and during storage
      • Contaminated food can cause fatal, acute illness and other chronic health risks.
      • Contaminated food can cause cancer
      • Affects trade and food security.
    • Hazards continued
      • Minute levels in food may cause severe poisoning in humans characterized by:
      • Acute liver damage
      • Cancer (Carcinogenicity)
      • Fetal Malformation (teratogenecity)
      • Estrogenic effects (female hormones)
      • Nervous effects (hallucinations)
      • Vomiting (emetic)
      • Immunosuppresion
    • Epidemiological associations in Kenya
      • Aflatoxins consumption and liver cancer as been demonstrated (hospital records in 4 hospitals in Meru and Makueni in the past)
      • Esophageal cancer attributed to fumonisin. (Bomet , Keiyo and Marakwet)
      • Contaminated weaning flour leading to kwashiorkor and impaired growth in children (Kisumu).
      • Over 82,000 cases of cancer diagnosed annually mainly due to dietary lifestyles (according to Dr. Mwangi, KNH)
    • Economic implications
      • Maize is the food of choice for over 85% of Kenyans with a per capita daily consumption of 0.4 kg
      • Maize is a major component of livestock feeds.
      • Retention of the toxic residues occur in foods of animal origin (milk, meat and eggs).
      • Health risk from primary and secondary exposure.
      • Studies by National Public Health Laboratories (NPHLS) in 2004/5 indicated aflatoxins levels as high as 46,000 ppb. in cereal samples.
      • The country wide survey found 21.7% of grains sampled had aflatoxins levels above 20 ppb.
      • In Eastern, Central, Rift Valley and Nairobi incidences with levels above 1,000 ppb were recorded.
    • Toxins of Aspergillus Spps.
      • 13 different aflatoxins are produced in nature. B 1 is the most toxic produced by both A. Parasiticus and A. flavus .
      • Aflatoxins G 1 and G 2 are produced by A. parasiticus only.
      • M 1 is a metabolite of B 1 in humans and animals and can be found in mother’s milk while M 2 is a metabolite of B 2 found in animal milk.
      • M 1 can intercalate into DNA causing mutation in the p53 gene which is important in preventing cell cycle progression.
      • Ochratoxin comes in three forms A, B and C. All are produced by Penicillium and Aspergillus spps the B and C are non chlorinated and ethyl ester respectively of OTA. It is common in wine and beer making and has been categorized as a carcinogen and nephrotoxin (linked to tumors in urinary tract).
      • Citrinin produced by Penicillium and Aspergillus spps found in rice, wheat, maize, barley, oats and rye. Citrinin can synergize with OTA to depress RNA synthesis in Kidneys.
    • Toxic effects of Mycotoxins in Humans 02/15/11
      Mycotoxin Fungi/ mould producer When produced Most susceptible commodity Toxic effect/ disease Aflatoxin Aspergillus flavus, A. Parasiticus Mainly post harvest, during storage Maize, cereals, groundnuts, tree nuts Liver damage (hepatitis) Liver cancer and death in case of acute cases Ochratoxins Aspergillus spps, Penicillium spps Mainly post harvest, during storage Cereals, Coffee, Cocoa, Spices and herbs Endemic balkan nephropathy- Kidney degeneration (common in eastern Europe) Citrinin Aspergillus spps, Penicillium spps Mainly post harvest Cereals and beverages Kidney damage Fumonisins Fusarium moniliforme Mainly pre harvest Maize, cereals Esophageal cancer Zealalenone (ZEN) Fusarium spps (especially F. roseum) Pre harvest and post harvest Mainly Cereals Oestrogenic effects (female hormone) cancer Deoxynivalenol (DON) Fusarium spp Especially F. graminearum Mainly pre harvest Cereals especially wheat, barley and maize Vomiting, enteritis (diarrhea), depressed immunity. Ergot Ergot alkaloids Mainly pre harvest Cereals especially barley, rye ,sorghum Localized tissue death (gangrene) and death.
    • Toxic effects of Mycotoxins in Domestic Animals 02/15/11
      Mycotoxin Fungi/ mould producer Toxic effect/ disease Aflatoxin Aspergillus flavus, A parasiticus
      • Acute liver damage and bleeding in tissue.
      • Depressed immunity and vaccination failure
      • Growth depression, reduced egg production
      • Cancer and deformed newborns.
      Ochratoxins Aspergillus spps, Penicillium spps
      • Kidney disease (nephritis) and degeneration (nephrosis) and enterittis in swine, calves and poultry
      • Reduced weight gain and lowered egg production
    • Factors that lead to Fungal Growth and Aflatoxins
      • Aflatoxins are formed as a result of fungal growth in agricultural commodities.
      • Once formed, they are extremely stable and persist long after the fungi has died.
      • Once contaminated the commodity remains toxic and injurious to those who consume it.
      • The toxins are produced under specific conditions compared to those required for normal fungal growth.
    • Factors that lead to Aflatoxins
      • Fungal growth and aflatoxins production is dependent on:
      • Presence of inoculums of a toxigenic fungal species.
      • A suitable substrate that may include agricultural commodities, processed foods, leather and wood.
      • Favourable environmental conditions
      • Moisture content of substrate
      • Temperature
      • Relative humidity
      • Oxygen / Carbon dioxide ratio
      • Time duration when all the above conditions are optimal
    • Factors leading to aflatoxins formation
      • Inoculums: The important producing fungi are Aspergillus, and are ubiquitous in occurrence and found in the air, soils, and vegetative materials.
      • Substrates: Fungi are able to colonize and grow in a wide variety of substrates that include organic materials and most commodities. But some commodities depending on varieties, physical damage and other factors are more susceptible. These include:
      • Maize, groundnuts, wheat and tree nuts.
      • ( Interesting to note maize is the main substrate for fumonisins)
    • Environmental conditions
      • Moisture is a very important factor in fungal growth and mycotoxins formation.
      • This includes the moisture content of the substrate and the relative humidity.
      • Most grains will be physiologically mature at moisture content of 20-35% and require to be dried to safe moisture levels to avoid fungal growth.
      • Most fungi will not grow at low or very high moisture levels. For example Aspergillus flavus does not grow well below 16% MC or above 85% RH
    • Environmental conditions Cont.
      • The rate of fungal growth depends on the temperature of the grain, slow and minimal in cool to cold grains and fast and extensive in warm grains.
      • The temperature will depend on ambient (environment) metabolic activity, aeration.
      • The optimal and maximum temperatures differ for different fungi but range from 0 o C to 50 o C.
      • The relative humidity favourable for fungal growth range from 65% - 80%
      • The Carbon / Oxygen ratio is important as most fungi will not grow in reduced oxygen conditions below 5%.
      • All other factors being optimal within a time duration of 48 -72 hours toxins will be produced and deposited in the substrate. In the case of aflatoxins, a duration of 4-7 days will result in maximum toxin production.
    • Factors and Critical Hazard Control Points 02/15/11
      Procedure Mycotoxins Application /Purpose Pre harvest (GAP) Seed Selection Aspergillus toxins Adaptability to fungal infection and ability to resist certain fungi. Ability to degrade aflatoxins in situ. Adaptability to ecological conditions. Resist pest damage and drought / moisture stress. Timely Planting Aspergillus and toxins Avoid growth stress at late stages of maturity/ Ensure timely harvest Spacing / Weeding / Fertilizer application / Irrigation Aspergillus toxins Avoid growth Stress (Moisture and Nutrients), increase water retention during growth. Ensure weed free seedbed to avoid pests and diseases. Fertilization ensures a healthy crop. Pest and Disease Control Aspergillus toxins Avoid grain damage by pests and easy mould formation. Avoid fungal inoculums dispersal Crop Rotation Aspergillus and Fumonisin Break proliferation of pathogen inoculums. Irrigation Aflatoxins and Fumonisins Avoid moisture stress during crop growth (irrigate or use drought tolerant varieties) Liming Aspergillus, Fusarium toxins Acidic soils stress the plant and predispose the plant to infestation Crop Residue management Aspergillus and Fusarium toxins Minimize inoculum's sources
    • Factors and Hazard Control Points cont. 02/15/11
      Procedure Mycotoxins Purpose / Application Harvesting / Post Harvest Timeliness Aspergillus toxins Fast drying of harvested produce at physiological maturity during the dry weather. Avoid prolonged standing in the field. Avoid partial and interrupted drying. Cleaning; sorting and grading Aspergillus toxins Remove potential contaminated kernels / remove easily infested kernels and remove carriers of heavy fungal innoculums/ avoid moisture retention during storage Drying Aspergillus toxins Arrest proliferation of toxigenic fungi at all stages of handling. Good storage practices Aspergillus toxins Avoid build up of moisture / moisture formation and retention. Control relative humidity. Avoid pest and vermin damage. Avoid temperature build up and avoid dissemination of fungal inocculums Good trade practices Aspergillus toxins Grading , sorting, cleaning and removal of contaminants. Avoid moisture build up and retention. Avoid fungal growth. Avoid pest infestation. Do not blend with old or poor quality
    • Identification of Aflatoxins Contaminated Grains
      • Very minute quantities are toxic
      • You cannot See , Smell , Feel or Taste Aflatoxins in grains.
      • Laboratory testing is required.
      • But you can suspect contaminated grains and avoid use or carry out tests.
    • Suspect Aflatoxins contamination in Grains
      • Grains with slight to severe mould growth and caking
      • Grains that are rotten, discoloured or diseased.
      • Grains with unusual or offensive smell, taste, flavour and aroma.
      • Moist / wet and warm / hot grains.
      • Death of dogs and birds such as pigeons after consumption of contaminated grains.
    • What to do with Aflatoxins Contaminated Grains
      • Aflatoxins in grains are stable and not easily destroyed or removed by cooking, washing, milling or other common food treatment.
      • Safest solution is:-
      • Destroy by Burning or bury deep.
    • Incidences of acute Aflatoxins poisoning in Kenya (findings not by Aflacontrol) 02/15/11
      Year Those affected Numbers affected Locality (District / Province Source of toxin Observed complications / effects 1960 Ducklings 16,000 White settler farms RVP Aflatoxin contaminated ground nut feed Death 1977 Dogs / Poultry Large numbers Nairobi / Mombasa / Eldoret Contaminated produce due to poor storage Death 1981 Human beings 12 Machakos Aflatoxin contaminated maize Death 1984 / 85 Poultry Large numbers Poultry farms Contaminated imported maize Death 1998 Humans Humans A few 3 Meru north Meru north Aflatoxin contaminated beans Aflatoxin contaminated maize Acute poisoning Death 2001 Humans 3 Meru north Mouldy Maize Death 2001 Humans 26 Maua Aflatoxin contaminated maize Severe liver damage. 16 deaths 2002 Dogs / Poultry Large numbers Coastal region Aflatoxin contaminated feed Death
    • Incidences of Acute Mycotoxins poisoning in Kenya cont.- 02/15/11
      Year Those affected Numbers Locality (District / Province) Source of poisoning Observed complications / effects. 2003 Humans 6 Thika Mouldy maize Death 2004 Humans 331 Eastern / Central Machakos, Kitui and Makueni Aflatoxin contaminated grains Acute poisoning 125 deaths 2005 Humans 75 Makueini, Kitui, Machakos Aflatoxin contaminated maize Acute poisoning 342 deaths 2006 Humans Over 20 cases Ndithini (Machakos), Mutomo (Kitui) Matiliku / Kisau (Makueni) Aflatoxin contaminated cereals Acute poisoning. 10 deaths reported in Mutomo as at 9 th June 2006 and 11 deaths as at 5 th June in Makueni. 2007 Humans 4 Kasekeu / Makindu Aflatoxin contaminated Maize 2 deaths reported as at 21 st May 2007 2008 Humans 5 high aflatoxins levels samples Isinya in Embu, Kibwezi and Mutomo Contaminated maize 3 persons hospitalized In Mutomo, 2 deaths reported in Kibewezi as at 5 th June 2008 2010 29 Districts in Eastern Kenya Suspect contaminated maize Price spiral down and grain trade break down. Unconfirmed cases of Dogs dying in Nairobi
    • Thank You
      • With the support of Bill and Melinda Gates Foundation