Aflatoxin Research in Kenya

Transcription

1 Aflatoxin Research in Kenya Australia Awards Africa Fellowships Short Course in Post-harvest Management of Maize, Rice and Legumes Royal Palm Room, Southern Sun Mayfair, Parklands Rd, Parklands, Nairobi Prof. James W. Muthomi Department of Plant Science and Crop Protection University of Nairobi

2 Case of aflatoxin poisoning in Kenya Cases of aflatoxin poisoning reported in Kenya from 1981 to 2010 Year Number of cases Number of deaths Areas of occurrence Machakos district Meru Eastern province Thika, Kitui, Makueni Kitui and Makueni Meru, Kitui, Makueni Eastern province Kitui (Mutomo) and Makueni Source; Lewis et al., 2005; KEPHIS, 2008; Daily nation Home grown maize implicated in most poisoning outbreaks; 2004 was the worst outbreak ever reported in the world - aflatoxin B 1 as high as 4,400 ppb

3 Aflatoxicosis outbreak in Eastern Kenya (CDC, KEMRI) 2004 aflatoxicosis outbreak was the largest ever described Most maize samples had excess of 5,000µg/kg aflatoxin B1 Most of the contaminated maize was homegrown (produced within) Main factors associated with highly contaminated maize: 1. Onset of rains during the harvesting season 2. Storage of inadequately dry maize 3. Storage in house as opposed to storage in granaries

4 Practices influencing aflatoxin contamination Poor harvesting practices, Drying practices Mechanical damage during shelling Improper storage and Less than optimal conditions during transport and marketing

5 Harvesting and drying practices Most small scale farmers dehusk the maize during harvesting and drop the cobs on the ground Some dry on polyethylene sheets or mats while others spread it on bare ground These drying methods are slow and may support growth and development of fungi

6 Shelling practices Shelling maize - the practice of beating the maize cobs by small scale farmers leads to damage of kernels Mechanical damage to maize kernels makes them much more vulnerable to invasion by storage moulds Cracks and breaks in maize are caused by harvesting and handling equipment

7 Post harvest handling and Storage

8 Insect damage Insect damage increases aflatoxin contamination Insects carry spores from plant surfaces to the interior of the stalk or kernels or create infection wounds

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10 Aspergillus flavus infection Aspergillus on maize Aspergillus on ground nuts

11 Fusarium ear rot Moulded maize Fusarium ear rot Fusarium red ear rot

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13 Types of storage structures Long term storage facilities Separate housing for storage Improved granary Silo Large pots Traditional crib Living house for storage Short term storage facilities Polypropylene sisal bags Baskets

14 2 Storage structures

15 Traditional crib A traditional storage structure made of local material available in a particular region. Cheap to construct, good ventilation and aeration thus reduces mouldy growths. Disadvantage - Insecure and requires seasonal repairs. Cribs made exclusively of plant materials rot fairly quickly, and most cribs have to be replaced every two or three years. Bamboo structures may last up to 15 years, with careful maintenance. 2

16 Improved granary An improved granary - made of wooden wall with supporting poles or stones and roofed with iron sheets. Granary has good ventilation and aeration thus discourages growth of moulds. 2

17 Living house for storage One room in the main house set aside for maize storage. Reason : Security Major disadvantage: May encourage growth of moulds and likelihood of aflatoxin infection due to high moisture in the house 2

18 BAGS Sisal bags Short duration storage facilities used widely in Kenya till the introduction of plastic bags. Polypropylene bags Short duration plastic bags widely used in Kenya. Sizes range from kg bags. Price affordable to most farmers. 2

19 Metal Silo An improved maize storage container made of metal sheet. Maize stored in the metal silo is not attacked by pests and is less infested by moulds. Aflatoxin levels reduced by 60% on average. Major disadvantage - High cost and the limited storage capacity 2

20 Matrix Scoring for three grain storage structures Metal bin Improved crib Traditional crib Durability of structure ***** ***** ** Ease of handling ***** ***** **** Peace of mind ***** *** *** Low construction costs * *** ***** Does not attract pests ***** **** ** Total Score:

21 Fusarium head blight on wheat Infected wheat field 12 Infected wheat ears Infected spikelets

22 2 Fusarium head blight

23 13 Identification of mycotoxigenic fungi

24 Mycotoxin management in food value chain: the case of aflatoxin in Kenyan maize 24

25 Maximum Mycotoxin Regulatory Limits (ppb) Commodity / use Mycotoxin FDA EU Codex Kenya Milk and milk products Aflatoxin M Maize (food) Aflatoxin B Maize (food) Total aflatoxins Maize (food) Fumonisins Maize products (food) Fumonisins Cereals and cereal Fumonisins ,000 60, products (feed) Maize (Feed) Aflatoxins Raw cereal grains (food) Ochratoxin A Unprocessed maize(food) Deoxynivalenol 1750 Cereal flour (food) - - Deoxynivalenol Cereals and cereal - - products (feed) Deoxynivalenol Maize by-products (feed) ,000 Unprocessed maize(food) Zearalenone Maize products (food) Zearalenone

26 Research areas in mycotoxins 1. Pre-harvest technologies crop residue management, breeding for resistance, drought tolerance, pest and disease management 2. Postharvest handling & storage storage structure, insect pest & mould management 3. Animals chicken, livestock products, feeds 4. Monitoring surveys, collaboration in national programmes, analysis, mould identification & detection 5. Food processing 6

27 Effect of different harvest intervals on incidence of ear rot fungi, fumonisin B1 and aflatoxin B1 (Alakonya, Monda, Ajanga and Owino) Investigated 4 maize varieties grown in Western Kenya in 2001 and 2003 Mycotoxins and fungi determined at 4, 8 and 12 weeks after physiological maturity (WAPM) FB1 detected in both clean and rotten maize samples FB1 increased with increased delay in harvesting (21.8 1,178µg/kg) FB1 in rotten maize ranged from >5,000µg/kg Highest aflatoxin level was 16.8µg/kg in rotten maize Dominant fungus was Fusarium verticillioides (80% incidence). Aspergillus Flavus incidence was up to 44%

28 Mycotoxin management in food value chain: the case of aflatoxin in Kenyan maize Percentage isolation frequency of Aspergillus spp from whole maize grain Mureithi et al

29 Mycotoxin management in food value chain: the case of aflatoxin in Kenyan maize CFU/g of Aspergillus species in soil and posho mill dust samples from lower eastern region of Kenya Mureithi et al

30 Mycotoxin management in food value chain: the case of aflatoxin in Kenyan maize Percentage isolation frequency of Aspergillus spp from whole maize grain Mureithi et al

31 Mycotoxin management in food value chain: the case of aflatoxin in Kenyan maize Percentage isolation frequency of Aspergillus spp in muthokoi from traders in eastern Kenya Mureithi et al

32 Mycotoxin management in food value chain: the case of aflatoxin in Kenyan maize Percentage isolation frequency of Aspergillus spp in maize flour from eastern Kenya Mureithi et al

33 Fungi and mycotoxins in freshly harvested wheat (Muthomi, Ndung u, Mutitu and Gathumbi) Wheat grain sampled at harvest during 2004 in Nakuru and Nyandarua Districts Mycotoxins DON, zearalenone, T-2 toxin and aflatoxin B1 detected Mycotoxin incidence and concentration in wheat: Nakuru and Nyandarua districts,2004 No. samples % incidence Range (µg/kg) Mean (µg/kg) DON ZEA T-2 toxin Aflatoxin B Main fungi: Fusarium, Epicoccum, Alternaria, aspergillus Main Fusarium spp: F. poae, F. graminearum, F. equiseti, F. chlamydosporum Muthomi, J. W. Fungi & mycotoxins in food grains 33

34 Mycoflora and mycotoxins associated with ear rot of maize in Central Kenya (Oduor, Mutitu, Narla and Gathumbi) Fusarium verticillioides (moniliforme) most predominant (59% of total fusaria) Other Fusarium spp.: F. graminearum, F. proliferatum, F. poae, F. oxysporum Aspergillus was low (5%) Incidence (%) Stored Ear rot Mycotoxin levels in ear rot maize (µg/kg) Fumonisin B ,000 DON ,000 Aflatoxin B Muthomi, J. W. Fungi & mycotoxins in food grains 34

35 Mycoflora and mycotoxins associated with ear rot of maize in Central Kenya (Oduor, Mutitu, Narla and Gathumbi) Mean level of mycotoxins in the ear rot groups Ear rot group Mean level (ppb) FB 1 DON AFB 1 Stalk borer 37,998 2, General rotting 28,637 2, Pink rot 34,409 9, Yellow rot 20,746 3,350 0 mean 30,448 4,

36 Grain drying practices Mureithi et al Percentage of farmers who dried maize in different forms in Easter and North Rift regions Form of drying Drying place District Shelled grains In cobs Bare ground Mats Eastern region Makueni Kitui Machakos Mean North Rift region Trans Nzoia Uasin Gishu Mean

37 Transportation practices Mureithi et al Percentage of traders who transported maize by different means District Vehicles Carts Bicycles People Donkeys back Eastern region Makueni Kitui Machakos Mean North Rift region Trans Nzoia Uasin Gishu Mean

38 Storage structures Mureithi et al Percentage of farmers who used different storage structures District House Cribs Traditional granary Improved stores Eastern region Makueni Kitui Machakos Mean North Rift region Trans Nzoia Uasin Gishu Mean

39 Storage materials Mureithi et al Percentage of traders and farmers using different storage materials Farmers Traders Polythen Sisal Synthetic Polythene Sisal Synthetic District e bag bag Bags Bags bag bag Eastern region Makueni Kitui Machakos Mean North Rift region Trans Nzoia Uasin Gishu Mean

40 Aflatoxin and fumonisin in samples from Makueni and Nandi Sample type NANDI Aflatoxin (% positive) Fumonisin (% positive) Maize (Market and homegrown (n= 305) Cow Milk (n= 246) 93 Breast Milk (n= 67) 59 Sorghum and millets (n=105) Children < 5 Urine (n= 362) 80 Feed samples (n= 207) MAKUENI Maize (Market and homegrown (n= 378) Cow Milk (n= 233) 93 Breast Milk ( n=98) 86 Sorghum and Millets (n=215) Children < 5 Urine (n= 377) 80 Feed Samples (n= 2) Kangethe et al

41 15 AREAS FOR ATTENTION 1. Mycotoxin legislative limits for all harzadous mycotoxins 2. Mycotoxin monitoring especially at local level majority of population feed of potentially contaminated foods 3. Simple, cheap and user friendly mytoxins detection kits that can used by publich health officers and traders in rural areas 4. Enhancing mycotoxin reference laboratories 5. Training of personell and continuous public awareness creation on mycotoxins

42 16 THANK YOU