Prof. James W. Muthomi Department of Plant Science and Crop Protection University of Nairobi 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
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Prof. James W. Muthomi Department of Plant Science and Crop Protection
University of Nairobi
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
Cases of aflatoxin poisoning reported in Kenya from 1981 to 2010
Year Number of cases Number of deaths Areas of
occurrence
1981 20 12 Machakos district 2001 - 12 Meru 2003 - 68 Eastern province
2004 317 125 Thika, Kitui,
Makueni
2005 75 32 Kitui and
Makueni
2007 84 21 Meru, Kitui,
Makueni 2008 6 2 Eastern province
2010 24 3 Kitui (Mutomo)
and Makueni
Source; Lewis et al., 2005; KEPHIS, 2008; Daily nation 2010. Home grown maize implicated in most poisoning outbreaks; 2004 was the worst outbreak ever reported in the world - aflatoxin B1 as high as 4,400 ppb
Case of aflatoxin poisoning in Kenya
Aflatoxicosis outbreak in Eastern Kenya - 2004 (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
Practices influencing aflatoxin contamination
•Poor harvesting practices,
•Drying practices
• Mechanical damage during shelling
•Improper storage and
•Less than optimal conditions during transport and marketing
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
•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
Shelling practices
Post harvest handling and Storage
•Insect damage
increases aflatoxin
contamination
•Insects carry spores
from plant surfaces to
the interior of the stalk or
kernels or create
infection wounds
Insect damage
Aspergillus on maize Aspergillus on ground nuts
Aspergillus flavus infection
Fusarium ear rot Fusarium red ear rot Moulded maize
Fusarium ear rot
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
2
Storage structures
2
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
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
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
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 25 - 100kg
bags.
Price affordable to most
farmers.
2
BAGS
2
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
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: 27 21 21
Infected wheat field
Infected wheat ears Infected spikelets
12
Fusarium head blight on wheat
2
Fusarium head blight
13
Identification of mycotoxigenic fungi
24
Mycotoxin management in food value chain: the case of
aflatoxin in Kenyan maize
25
Maximum Mycotoxin Regulatory Limits (ppb) Commodity / use Mycotoxin FDA EU Codex Kenya