The presence and growth of Aspergillus on preharvested crops can be reduced through agricultural practices such as proper irrigation and pest management. Preharvest interventions include choosing crops with resistance to drought, disease, and pests and choosing varieties that are genetically more resistant to the growth of the fungus and the production of aflatoxins (Chen et al. 2001; Cleveland et al. 2003; Cotty and Bhatnagar 1994). Elimination of inoculum sources, such as infected debris from the previous harvest, may prevent infection of the crop (Olanya et al. 1997). A biopesticide consisting of a nonaflatoxigenic strain of Aspergillus may competitively exclude toxic strains from infecting the crop (Cleveland et al. 2003; Dorner et al. 1999). However, the allergenic and human health aspects of the atoxigenic strain need to be evaluated.

Before storage, properly drying crops can prevent the development of aflatoxins. Sorting and disposing of visibly moldy or damaged kernels before storage is an effective method for reducing but not eliminating the development of aflatoxins (Fandohan et al. 2005a; Turner et al. 2005). Moisture, insect, and rodent control during storage can prevent damage to the crop, which would promote aflatoxin development. Aflatoxin contamination of maize is influenced by the structure used for storage, the length of time in storage, and the form of maize stored (i.e., with husk, without husk, or loose grain) (Hell et al. 2000). A community-based intervention trial in Guinea, West Africa, focused on thorough drying and proper storage of groundnuts in subsistence farm villages (Turner et al. 2005). The trial achieved a 60% reduction in mean serum aflatoxin–albumin levels in people in intervention villages. This study illustrates that simple and inexpensive postharvest methods can have a significant impact.

Interventions during food preparation or consumption involve removing contaminated portions of food, diluting contaminated food with uncontaminated food, neutralizing aflatoxins present in food, or altering the bioavailability of the aflatoxins consumed. Simple food preparation methods such as sorting, washing, crushing, and dehulling may reduce aflatoxin levels (Fandohan et al. 2005b; Lopez-Garcia and Park 1998; Park 2002). Aflatoxins are not largely affected by routine cooking temperatures, but traditional methods of cooking food with alkaline compounds (i.e., nixtamalization) have been used to reduce aflatoxin exposure. Although the chemical reaction may temporarily inactivate aflatoxins, the reaction may then reverse in the gastric acid of the stomach (Elias-Orozco et al. 2002; Fandohan et al. 2005b; Mendez-Albores et al. 2004; Price and Jorgensen 1985).

Additional strategies for reducing aflatoxins, including enterosorption and chemoprotection, attempt to reduce the effects of aflatoxin exposure or the bioavailable portion of aflatoxins in food. Enterosorption is the use of clay, such as NovaSil, a processed calcium montmorillonite clay with a high affinity for aflatoxins (Phillips 1999; Phillips et al. 2002; Wang et al. 2005). Clay has been used as an anticaking additive in animal feed and has been shown to protect animals from ingested aflatoxins. Chemoprotection is the use of chemical {e.g., oltipraz [4-methyl-5-(2-pyrazinyl)-1,2-dithiole-3-thione], chlorophylin} or dietary intervention (e.g., eating broccoli sprouts, drinking green tea) to alter the susceptibility of humans to carcinogens and has been considered as a strategy to reduce the risk of HCC in populations with high exposures to aflatoxins (Bolton et al. 1993; Kensler et al. 1994, 2004; Wang et al. 1999). These strategies, however, are expensive and are therefore difficult to implement in poor communities. The efficacy, safety, and acceptability of enterosorption and chemoprotection require further study.

During the 2005 Kenya outbreak, individuals who received information on maize drying and storage through an awareness campaign run by the Food and Agricultural Organization and Kenya’s Ministry of Health and Ministry of Agriculture had lower serum aflatoxin levels than those who did not receive this information (CDC, unpublished data). Awareness campaigns should use systems that are in place already for disseminating information to subsistence farmers (James 2005). Awareness campaigns should distribute information to multiple organizations and use multiple means for spreading information to reach a broad range of people, given the diversity of cultures and remoteness of villages. Organizations providing information need to identify groups that are not receiving messages from current campaigns and appropriate methods for reaching those populations. They should also determine why individuals or groups are unwilling or fail to adopt recommendations.

Testing food for aflatoxins is constrained by two limitations. First, obtaining a representative sample of food from subsistence farmers is difficult given the need for large samples, multiple vulnerable crops on one farm, the distance between farmers, villages, and laboratories, and uneven distribution of aflatoxin contamination within a food supply.

Second, little is known about the specific threshold levels associated with adverse health effects. Agricultural data have established a relationship between concentrations of aflatoxins in food and acute aflatoxicosis. This has led to regulatory limits on aflatoxin in feed of 100–300 ppb for mature animals and 20–100 ppb for immature and dairy animals in the United States (Phillips et al. 1994). Limits for foods for human consumption in the industrialized world (including exports from developing countries) are 4–20 ppb; those limits are based on limited information from risk assessments of HCC (Henry et al. 1999; van Egmond 2002). Information is extremely limited concerning health effects associated with aflatoxin concentrations between 20 ppb and 300 ppb.

For epidemiologic studies, biomarkers in serum and urine provide a better estimate of aflatoxin exposure than does food analysis. Aflatoxin metabolites in urine reflect recent exposure (i.e., 2–3 days), whereas aflatoxin albumin adducts in blood reflect exposure over a longer period (i.e., 2–3 months) (Groopman et al. 1994). These analyses, however, are labor intensive and expensive (McCoy et al. 2005; Sheabar et al. 1993; Wild et al. 1990).

Information regarding the interpretation and application of AFB₁ adducts and urine immunoassays is also limited (Groopman and Kensler 2005; Turner et al. 1998; Wild and Turner 2001). Aflatoxin metabolites or adducts in urine and serum indicate exposure, but do not necessarily equate to adverse health effects. Some studies have examined the correlation of aflatoxin intakes to biomarker levels (Groopman et al. 1992; Wild et al. 1992) and to disease (Azziz-Baumgartner et al. 2005; Gong et al. 2004; Qian et al. 1994; Wang et al. 1996). More research is needed to further elucidate the correlation between aflatoxin levels in biologic specimens and adverse health effects. Research must also clarify the relationship between aflatoxin levels in biologic specimens and levels in food.

Simple and inexpensive field screening methods, such as portable, lateral flow immunochromatographic assays, are available to determine that food is sufficiently free of aflatoxins. Field methods can be performed with minimal training or equipment and can be performed onsite (i.e., at a farm or grain silo). Field methods for aflatoxin analysis allow for rapid confirmation or exclusion of possible exposure at a reasonable cost, thus allowing officials to quickly determine the need for further evaluation and intervention. Such methods would prove beneficial in developing countries where the remoteness of villages and long distances to a centralized laboratory make it impractical to take samples from villages, analyze them in the laboratory, and then travel back to the village to deliver the results.

Currently, however, these lack direct applicability in developing countries. For example, one field screening method uses dipsticks that indicate whether a sample is above or below the regulatory limit of 20 ppb. In developing countries, especially during an outbreak, most samples would be > 20 ppb. Therefore, an investigator would need to differentiate between samples at levels > 20 ppb. Such field tests could prove effective if they were adjusted to action levels suitable for developing countries. Field methods for the analysis of biologic samples have not been developed. However, the same concept of using dipsticks can be applied to field tests for biologic specimens. Efforts to limit aflatoxin exposure in developing countries could be enhanced by reducing the cost and improving the durability, ease of transport, and usability of field methods. Ideally, such methods should be easy to use and should not require electricity.

Laboratory methods can be used to confirm results of field tests. They are more precise, but also more labor intensive and costly. These methods require instrumentation or techniques not suited to working onsite. They require regular maintenance of instrumentation, training of personnel, and a ready supply of reagents and materials (Trucksess and Wood 1994). The best laboratory method for testing either food or biologic specimen is one that balances the need for quick, accurate results with limitations in resources and infrastructure. Current laboratory methods require further refinement to improve their usability in developing countries. Thin-layer chromatography is a well-suited laboratory method for testing food samples, given its reliability and simplicity (Shephard and Sewram 2004; Stroka and Anklam 2000). It is labor intensive, however, and limited in the number of samples that can be tested in a day. Alternatives for food analysis include commercially available aflatoxin testing kits, which are less labor intensive and faster, but also more expensive (Scott and Trucksess 1997).