Intervention strategies against aflatoxins

Aflatoxins are clearly of public health importance, although at present the full-scale of their impact is difficult to estimate. Nevertheless, the effects on child growth, hepatocellular carcinoma and the incidence of aflatoxicosis suggest reducing exposure is a valid public health goal (Strosnider et al., 2006). In addition, reducing contamination of foods with aflatoxins would have benefits both in reducing food spoilage in communities where food often is scarce and in making the foodstuffs more desirable in world markets (Wu, 2004).

A number of strategies for reducing aflatoxin exposure or the biological effects once ingested have been discussed (Wild and Hall, 2000). These include pre-harvest interventions (for example, better irrigation, use of pesticides, fungicides, biocontrol or genetic modification to improve crop resistance), post-harvest measures (for example, better drying and storage) or chemoprevention. In our own studies in West Africa we have focused on post-harvest measures because much of the contamination occurs at this stage and post-harvest approaches are simple and cheap compared to many other strategies. In particular, we consider methods that can be implemented at the subsistence farm level rather than the larger-farm scale approaches, e.g., Hazard Analysis and Critical Control Point (HACCP), whose strategies may not be readily applicable to small-scale farmers.

In a community intervention study in Guinea (Turner et al., 2005a), we implemented a number of measures to reduce fungal growth and toxin production post-harvest on the peanut crop; peanuts are the main dietary staple in the lower Kindia region of Guinea where the study was conducted. None of the introduced practices were new to the local farmers but they typi cally are used sporadically and without any training. The implemented intervention package comprised: drying the crop thoroughly in the sun; drying peanuts on mats rather than the ground; hand sorting to discard visibly moldy kernels or nuts before storage; use of natural fiber sacks for storage, rather than plastic bags that promote humidity; placing storage sacks on wooden pallets to avoid dampness; and using insecticide to reduce insect damage to the crop.

The intervention was conducted over a five month period in sixteen villages: eight intervention villages and eight control. The eight control villages followed their usual post-harvest practices. AF-alb was measured in 600 subjects at three time points. In the control villages the mean AF-alb levels increased post-harvest, whereas in the intervention villages the levels after 5 months of storage were similar to that immediately post-harvest. Mean AF-alb levels at this time were 60% lower in intervention villages than in the control villages (p < 0.001; Fig. 2A). The number of subjects with non-detectable levels of adduct at the time of harvest was ~30%. This value decreased to 2% five months later in control villages, but to only 20% in the intervention group over the same time (p < 0.001; Fig. 2B). The mean level of aflatoxin B1 in peanuts in household stores in intervention and control villages mirrored the pattern seen for AF-alb levels. The effectiveness of this intervention suggests that significant reductions in exposure to this potent environmental toxin can be achieved by using low technology approaches at the subsistence farm level in sub-Saharan Africa.

This work provides evidence that aflatoxin exposure is preventable on a community basis with low cost input. The use of the aflatoxin-albumin biomarker enabled the impact of aflatoxin reduction measures on human exposure to be assessed, as opposed to simply demonstrating lower levels in food commodities in field trials. We are now conducting a similar intervention to assess the impact of reduced aflatoxin exposure on child growth and immunity in villages in Guinea. This information will provide an indication of the benefits of such strategies, not just in reducing aflatoxin exposure but also in terms of reduced morbidity in these populations.

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