aflatoxin basics

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

Aflatoxin Basics

Food Systems

• Large Scale and Regulated – Developed countries– Trade based– Advanced infrastructure– Capital intensive

Tim Williams, Peanut CRSP

Small Scale and Unregulated – Developing countries– Informal markets– Subsistence– High food insecurity

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• Highly toxic metabolite produced by the ubiquitous Aspergillus flavus fungus

• The fungus resides in soil and crop debris, infects crops and produces the toxin in the field and in stores

Aflatoxin FactsAflatoxin Facts

• Contamination possible without visible signs of the fungus

• Fungus carried from field to store

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• Unlike most fungi, Aspergillus flavus is favored by hot dry conditions.

• The optimum temperature for growth is 37 C, but the fungus readily grows between the temperatures of 25-42 C, and will grow at temperatures from 12-48C.

• Toxin contamination more when night temperatures are high

• Drought stress predisposes plants to aflatoxin

Disease Development & Weather

Source: www.aspergillusflavus.org

http://www.aspergillusflavus.org/images/cycle.jpg

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Aflatoxin Contamination Occurs in Two Phases

Phase I: Before Crop Maturity Developing crops become infected. Associated with crop damage (insect, bird, stress). Favored by high temperature (night) and dry conditions.

Phase II: After Crop Maturity Aflatoxin increases in mature crop. Seed is vulnerable until consumed. Rain on the mature crop increases contamination. Associated with high humidity in the field & store, insect

damage, and improper crop storage or transportation.

Contamination is most severe at low elevations and during dry periods. During drought the zone with contamination expands.

35°N

35°S Zone with PerennialContamination Risk

Aflatoxin Contamination: A Perennial Concern in Warm Climates

Prevalence of Aflatoxins in Food & Feed

• Several African staple commodities affected• High human exposure in Africa – mother to baby• Levels and frequency of occurrence high• Concern for food and feed processors, government

and emergency food reserve agencies, school-feeding

• Aflatoxins disproportionately impact the poor• Highly toxic strains, conducive environmental

conditions, traditional farming methods and improper grain drying and storage practices, unregulated markets


Aflatoxin Contamination in West Africa

• Maize: 4,000 – Benin• Peanut: 925 – Burkina• Sorghum: 80 – Ghana• Rice: 372 – Nigeria• Millet: 200 – Nigeria• Tiger nuts: 120 – Nigeria

Primary products• Peanut paste: 3,278 – Ghana• Peanut sauce: 943 – Ghana• Leaf sauce: 775 – Gambia• Maize dough: 313 – Ghana• Kenkey: 524 – Ghana• Cashew paste: 366 – Ghana• Peanut oil: 500 – Nigeria• Yam flour: 7,600 – Nigeria• Local beer: 135 – Nigeria• Infant food: 19* –

Burkina

Food productsMTL = 10 - 20 ng/g


Aflatoxin Exposure in Africa• Exposure to aflatoxin in sub-Saharan Africa is

common and at high levels – important exposure occurs at the small subsistence farm level

• Exposure begins in utero and continues throughout life, with a reduced exposure during breastfeeding

• Exposure in young children is associated with impaired growth and development

• Under-nutrition and growth faltering is an underlying cause of 50% of deaths in children <5 years age (Black et al., Lancet, 2003)


Aflatoxin and Human Health Death Binds with DNA -- mutagenic Type I carcinogen Causes liver cancer – increasing incidence Aflatoxin interacts with HBV• 30 times more potent in HBV+ people• 5-60 times higher cancer risk• 40% of liver cancer cases linked to aflatoxin Associated with stunting in children Associated with immune suppression Impede uptake and utilization of micronutrients in

human systems Associated with Kwashiorkor in children Contributes to 40% of DALYs


Animal Health Impact of Aflatoxin

Livestock and poultry losses liver damage including cancer recurrent infection due to

immune system suppression reduced growth rate losses in feed efficiency decreased milk and egg yield embryo toxicity (reduced

reproductivity) death (cattle, turkey, poultry,

swine..)

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Aflatoxin and Poultry (Broilers)Aflatoxin and Poultry (Broilers)

Aflatoxin levels in feeds in Nigeria

Aflatoxin level (ppb) Samples (%)

<20 (safe) 38

>20 to 100 (up to 5x) 14

>100 to 500 (up to 25x) 41

>500 to 1,000 (up to 100x) 7

AF-free diet 500 ppb AF dietAF-freediet

500 ppb AF diet

~40% reduction in live weight (8 weeks)

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Trade Losses due to Aflatoxins

• Nigeria and Senegal major groundnut exporters in 1960s. Compliance has economic incentives

• Senegal: US$ 4.1 million added capital investment and 15% recurring cost would attract 30% price differential to oil cake.

• Export would increase from 25K tons to 210K tons.

• Increased export volume and price differential would annually add $281 million value to groundnut export for the capital investment.

• For confectionary groundnut, adherence to Good Management Practices would increase export value by US$ 45 million annually.

• Best quality exported; poorer quality consumed domestically. Peanut

Maize

Coffee

Cocoa

Groundnut Pyramids in Nigeria during 1960sPyramids in Egypt?

World Bank; Mbaye (2004)


EU Rejections of Imports According to Risks

SOURCE: EU Rapid Alert System For Food and Feed (RASFF, 2005)


Product: Aflasafe

Mixture of 4 native atoxigenic strains

Nigeria


Summary

• Aflatoxins in food and feed pervasive in Africa.

• Negative impact overlooked – chronic, unseen.

• Serious effect on children’s growth & development.

• Export potential of primary raw material unrealized.

• Even greater potential in domestic/regional markets

• Institutions related to food safety very weak.

• New approaches required to manage aflatoxin.

aflatoxin basics

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