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www.iita.org A member of CGIAR consortium
Juliet Akello
Techniques for mitigating aflatoxin-producing fungi
The Silent Killer: Aflatoxins
www.iita.org A member of CGIAR consortium
About IITA
IITA
Aflatoxin:
What they are
Drivers
Status in sub-Saharan Africa
Interventions
Future research prospects
www.iita.org A member of CGIAR consortium
About IITA
International research organization
founded in 1967
Develop sustainable food production
systems in tropical Africa
Most important African link in
CGIAR
198 scientists and > 2,000 staff
Operate throughout sub-Saharan
Africa
Research along entire value chain
Lusaka
www.iita.org A member of CGIAR consortium
Highly toxic metabolite produced by
the fungus Aspergillus section Flavi
Common & widespread fungus in soil
& decaying matter
Fungus is sometimes visible, toxin is
not
Aspergillus
What is Aflatoxin?
Aflatoxin
www.iita.org A member of CGIAR consortium
Types of aflatoxin
Aflatoxin
13 different types of aflatoxin are produced in nature
Most common: aflatoxins B1, B2, G1 & G2
Aflatoxin B1 is the most toxic.
Aflatoxin M1:
• breakdown product of Aflatoxin B1
• excreted in the urine & milk of exposed humans/
animals.
Aflatoxin contamination: causative agent
A. flavus L- strain A. flavus S- strain A. parasiticus
+++++
- / +
Aflatoxin-producing Aspergillus spp
Aflatoxin contamination: causative agent
Reverse
Front
A. oryzae A. sojae A. tamarii
8
Colony & Microscopic Characteristics
Rough conidia
Smooth conidia
A. parasiticus
A. flavus
www.iita.org A member of CGIAR consortium
Aspergillus Spp. & Aflatoxins
Ability to produce aflatoxins in A. flavus strains varies
Some strains produce a lot (toxigenic) & others little or no aflatoxins
(atoxigenic)
Species/strain B aflatoxin G aflatoxin
A. flavus ‘L-strains’ +/- -
A. flavus ‘S-strains’ + -
A. flavus ‘SBG strains’ + +
A. parasiticus + +
A. nomius + +
A. tamarii - -
Maize
SUCEPTIBLE CROPS: MANY
Cassava
Cashew nut Groundnut
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Aflatoxin contamination: when does it occur?
Phase 1: Before crop maturity
a. Developing crop becomes infected
b. Linked to crop damage (pests,
stress)
Phase 2: After crop maturity
a. Aflatoxin increases with crop
maturity
b. May occur before or after
harvest
c. Seed is vulnerable till consumed
Occurs in 2 phases
SYMPTOMS OF FUNGAL CONTAMINATION
Infected maize cobs
Maize
Clean maize
SYMPTOMS OF FUNGAL CONTAMINATION
Clean groundnut Infected groundnut
SYMPTOMS OF FUNGAL CONTAMINATION
Contaminated cassava
Clean cassava
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a) Susceptible crops b) Favorable climate
Infection before crop maturity: plant stress (high T, drought)
Aflatoxin problem in SSA: drivers
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Aflatoxin contamination: monitoring
Monitoring starts in the field
• diseased plant parts
• Sampling
www.iita.org A member of CGIAR consortium
Aflatoxin contamination: monitoring
Monitoring continues in the lab
• Black light (UV light-365nm)-
for greenish gold fluorescence
• Commercial test kits
www.iita.org A member of CGIAR consortium
Aflatoxin prevalence in foods & feeds in SSA
• Several African staple commodities affected
• High human exposure in Africa – mother to baby
• Levels and frequency of occurrence high
– >30% maize in stores with >20 ppb aflatoxin
– ~90% stores are contaminated with Afla fungi
– Up to 40% grain in households with aflatoxin
www.iita.org A member of CGIAR consortium
Aflatoxin prevalence in foods & feeds in SSA
• Several African staple commodities affected
• High human exposure in Africa – mother to baby
• Levels and frequency of occurrence high
– >30% maize in stores with >20 ppb aflatoxin
– ~90% stores are contaminated with Afla fungi
– Up to 40% grain in households with aflatoxin
AFLATOXIN IN ZAMBIA
0
20
40
60
80
100
2011/2012 2013/2014
To
xig
en
ic s
tra
ins (
%)
Atoxigenic
Toxigenic
Aflatoxin producing fungus (Aspergillus) in Zambian soils
fungus colonizing groundnut root zones in soils
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Year Maize Groundnut Reference
1979 - 5 Kannaiyan et al. 1979
1998 900-929 6200-8600 Njapau et al. 1998
2009 0.7-108.4 - Kankolongo et al. 2009
2010 10 - Mukanga et al. 2010
2012/2013 0-255 0-5350 IITA-unpublished
Aflatoxin levels (ppb) detected in maize & groundnut samples from different
parts of Zambia
Surveillance studies
Aflatoxin levels depended on: locality, crop, processing method &
presence of microbial contaminants
FACTORS PROMOTING CONTAMINATION
a) Late planting and harvest
FACTORS PROMOTING CONTAMINATION
b) Poor drying techniques
FACTORS PROMOTING CONTAMINATION
c) Poor storage and informal marketing systems
d) Lack of awareness & inadequate regulatory systems
Aflatoxin problem in SSA: drivers
FACTORS PROMOTING CONTAMINATION
d) Favorable climate (High temperatures and drought/
dry periods) and insect pests
35°N
35°S
HARMFUL EFFECTS OF AFLATOXIN
Taiwan
1967
Uganda
1970
Western India
1974
Kenya
1982
2002
2004
2005
2006
2007
2008
Malaysia
1988
35°N
35°S
Causes death: history of Acute Outbreaks
HARMFUL EFFECTS OF AFLATOXIN
Causes poisoning and death: Acute toxicity in humans are rare, but deaths have been reported
40 deaths in 1974 (India); 13 deaths in 1990 in Malaysia
14 deaths in 2001 (Kenya); > 200 deaths in 2010 (Kenya)
HARMFUL EFFECTS OF AFLATOXIN
• Enhances stunting and underweight in children
HARMFUL EFFECTS OF AFLATOXIN
• Causes liver rot, enlarged liver, and liver cancer
• Enhances susceptibility to illnesses
• Suppresses the immune system
HARMFUL EFFECTS OF AFLATOXIN
Up to 3.4 increment in Feed conversion ratio
Livestock and poultry losses
losses in feed efficiency
Recurrent infection due to losses in feed efficiency
Bird mortality
HARMFUL EFFECTS OF AFLATOXIN
40% reduction in live weight
500 ppb AF diet AF-free diet
Livestock and poultry losses
reduced growth rate
AF-free diet
HARMFUL EFFECTS OF AFLATOXIN
Livestock and poultry losses
decreased milk & egg yield
embryo toxicity (reduced
reproductivity)
death (cattle, turkey, swine..)
Carry over: high levels
Meat, eggs, Gizzards, Diary products, Kidneys & cheese
HARMFUL EFFECTS OF AFLATOXIN
Aflatoxin, a threat to trade! Serious Trade Barrier (Market exclusion)
~2.3 M bags untradeable Many SSA unable to sell
<4 <10 <20 <10
EU WFP US COMESA
Acceptable Limits (ppb)
>20
unsafe
CODEX Alimetarius Commission
Regulatory standard: 20 ppb
REDUCING AFLATOXIN CONTAMINATION
1. Awareness, advocacy & training
Early harvest, proper drying and storage
REDUCING AFLATOXIN CONTAMINATION
REDUCING AFLATOXIN CONTAMINATION
Maintain crop hygiene at all levels: sorting/ physical
separation, and destruction of contaminated grains
REDUCING AFLATOXIN CONTAMINATION
Use of mechanical groundnut sheller instead of wetting
BIOLOGICAL CONTROL OF AFLATOXIN
AflaSafe biopesticide
Mixture of 4 atoxigenic
strains of A. flavus of local
origin
BIOLOGICAL CONTROL OF AFLATOXIN
At application: Maize
Broadcast aflasafe by hand 2 to 3 weeks before flowering by
broadcasting at a rate of 10 kg/ha
BIOLOGICAL CONTROL OF AFLATOXIN
At application: Groundnut
Apply aflasafe between 30 to 40 days after planting by side
dressing along the rows on the soil surface (rate of 10 kg/ha).
www.iita.org A member of CGIAR consortium
Aflatoxin mitigation: what can be done?
Detection systems
Management options
Afla-ELISATM, AcuScan flow readers
Africa-wide surveillance fungal populations, climate change, predictive modeling
Plant breeding resistant maize/ groundnut lines
AflasafeTM
Mycotoxin assessment
research pathway example of research
Technology adoption
Capacity building