A Critical Review of Aflatoxin Contamination of Peanuts in Malawi and Zambia: The Past, Present, and Future

Aflatoxin Contamination: An Overview on Health Issues, Detection and Management Strategies

Aflatoxins (AFs) represent one of the main mycotoxins produced by Aspergillus flavus and Aspergillus parasiticus, with the most prevalent and lethal subtypes being AFB1, AFB2, AFG1, and AFG2. AFs are responsible for causing significant public health issues and economic concerns that affect consumers and farmers globally. Chronic exposure to AFs has been linked to liver cancer, oxidative stress, and fetal growth abnormalities among other health-related risks. Although there are various technologies, such as physical, chemical, and biological controls that have been employed to alleviate the toxic effects of AF, there is still no clearly elucidated universal method available to reduce AF levels in food and feed; the only mitigation is early detection of the toxin in the management of AF contamination. Numerous detection methods, including cultures, molecular techniques, immunochemical, electrochemical immunosensor, chromatographic, and spectroscopic means, are used to determine AF contamination in agricultural products. Recent research has shown that incorporating crops with higher resistance, such as sorghum, into animal feed can reduce the risk of AF contamination in milk and cheese. This review provides a current overview of the health-related risks of chronic dietary AF exposure, recent detection techniques, and management strategies to guide future researchers in developing better detection and management strategies for this toxin.

Aflatoxin in cereals and groundnut from small holder farming households in Malawi

Aflatoxin contamination in commonly consumed cereals and nuts may place children at higher risk of stunting and adults at risk of developing liver cancer. This study investigated knowledge on aflatoxins and the level of aflatoxin B₁ contamination in commonly consumed cereals and nuts in Malawi. It also included an examination of the proportion of cereals and nuts contaminated above regulatory maximum limits. Aflatoxin contamination in samples was assessed using an enzyme-linked immunosorbent assay (ELISA) method. Less than half of all households knew that consumption of aflatoxin contaminated grain is associated with stunting and lowered immunity. Sorghum samples were the most contaminated and millet the least contaminated. Aflatoxin contamination was highest in southern Malawi and least in northern Malawi. Observed results indicate that this population is at risk of poor health due to lack of knowledge and aflatoxin exposure. Strategies to address contamination should therefore include a comprehensive education campaign to increase knowledge and promote accessible strategies.

Impact of frequency of application on the long-term efficacy of the biocontrol product Aflasafe in reducing aflatoxin contamination in maize

Aflatoxins, produced by several Aspergillus section Flavi species in various crops, are a significant public health risk and a barrier to trade and development. In sub-Saharan Africa, maize and groundnut are particularly vulnerable to aflatoxin contamination. Aflasafe, a registered aflatoxin biocontrol product, utilizes atoxigenic A. flavus genotypes native to Nigeria to displace aflatoxin producers and mitigate aflatoxin contamination. Aflasafe was evaluated in farmers' fields for 3 years, under various regimens, to quantify carry-over of the biocontrol active ingredient genotypes. Nine maize fields were each treated either continuously for 3 years, the first two successive years, in year 1 and year 3, or once during the first year. For each treated field, a nearby untreated field was monitored. Aflatoxins were quantified in grain at harvest and after simulated poor storage. Biocontrol efficacy and frequencies of the active ingredient genotypes decreased in the absence of annual treatment. Maize treated consecutively for 2 or 3 years had significantly (p < 0.05) less aflatoxin (92% less) in grain at harvest than untreated maize. Maize grain from treated fields subjected to simulated poor storage had significantly less (p < 0.05) aflatoxin than grain from untreated fields, regardless of application regimen. Active ingredients occurred at higher frequencies in soil and grain from treated fields than from untreated fields. The incidence of active ingredients recovered in soil was significantly correlated (r = 0.898; p < 0.001) with the incidence of active ingredients in grain, which in turn was also significantly correlated (r = -0.621, p = 0.02) with aflatoxin concentration. Although there were carry-over effects, caution should be taken when drawing recommendations about discontinuing biocontrol use. Cost-benefit analyses of single season and carry-over influences are needed to optimize use by communities of smallholder farmers in sub-Saharan Africa.

Peanut Butter Food Safety Concerns-Prevalence, Mitigation and Control of Salmonella spp., and Aflatoxins in Peanut Butter

Peanut butter has a very large and continuously increasing global market. The food safety risks associated with its consumption are also likely to have impacts on a correspondingly large global population. In terms of prevalence and potential magnitude of impact, contamination by Salmonella spp., and aflatoxins, are the major food safety risks associated with peanut butter consumption. The inherent nature of the Salmonella spp., coupled with the unique chemical composition and structure of peanut butter, present serious technical challenges when inactivating Salmonella spp. in contaminated peanut butter. Thermal treatment, microwave, radiofrequency, irradiation, and high-pressure processing all are of limited efficacy in inactivating Salmonella spp. in contaminated peanut butter. The removal of aflatoxins in contaminated peanut butter is equally problematic and for all practical purposes almost impossible at the moment. Adopting good manufacturing hygiene practices from farm to table and avoiding the processing of contaminated peanuts are probably some of the few practically viable strategies for minimising these peanut butter food safety risks. The purpose of this review is to highlight the nature of food safety risks associated with peanut butter and to discuss the effectiveness of the initiatives that are aimed at minimising these risks.

Selection of Atoxigenic Aspergillus flavus for Potential Use in Aflatoxin Prevention in Shandong Province, China

Aspergillus flavus is a common filamentous fungus widely present in the soil, air, and in crops. This facultative pathogen of both animals and plants produces aflatoxins, a group of mycotoxins with strong teratogenic and carcinogenic properties. Peanuts are highly susceptible to aflatoxin contamination and consumption of contaminated peanuts poses serious threats to the health of humans and domestic animals. Currently, the competitive displacement of aflatoxin-producers from agricultural environments by atoxigenic A. flavus is the most effective method of preventing crop aflatoxin contamination. In the current study, 47 isolates of A. flavus collected from peanut samples originating in Shandong Province were characterized with molecular methods and for aflatoxin-producing ability in laboratory studies. Isolates PA04 and PA10 were found to be atoxigenic members of the L strains morphotype. When co-inoculated with A. flavus NRRL3357 at ratios of 1:10, 1:1, and 10:1 (PA04/PA10: NRRL3357), both atoxigenic strains were able to reduce aflatoxin B₁ (AFB₁) levels, on both culture media and peanut kernels, by up to 90%. The extent to which atoxigenic strains reduced contamination was correlated with the inoculation ratio. Abilities to compete of PA04 and PA10 were also independently verified against local aflatoxin-producer PA37. The results suggest that the two identified atoxigenic strains are good candidates for active ingredients of biocontrol products for the prevention of aflatoxin contamination of peanuts in Shandong Province.

The potential for aflatoxin predictive risk modelling in sub-Saharan Africa: a review

This review presents the current state of aflatoxin risk prediction models and their potential for value actors throughout the food chain in sub-Saharan Africa, with a specific focus on improving smallholder farmer management practices. Several empirical and mechanistic models have been developed either in academic research or by private sector aggregators and processors in high-income countries including Australia, the USA, and Southern Europe, but these models have been only minimally applied in sub-Saharan Africa, where there is significant potential and increasing need due to climate variability. Predictions can be made based on historic occurrence data using either a mechanistic microbiological framework for aflatoxin accumulation or an empirical model based on statistical correlations with climate conditions and local agronomic factors. Model results can then be distributed to smallholders through private, public, or mobile extension services, used by policymakers for strategy or policy, or utilised by private sector institutions for management decisions. Specific agricultural advice can be given during the three most critical points in the phenological cycle: preseason insight including sowing timing and crop varieties, preharvest advice about management and harvest timing, and postharvest optimal practices including storage, drying, and market information. Model development for sub-Saharan Africa is limited by a dearth of georeferenced aflatoxin occurrence data and real-time high resolution climate data; the wide diversity of farm typologies each with significant information and technology gaps; a prevalence of informal market structures and lack of economic incentives systems; and general lack of awareness around aflatoxins and best management practices to mitigate risk. Given advancements towards solving these challenges, predictive aflatoxin models can be integrated into decision support platforms to focus on optimisation of value for smallholders by minimising yield and nutritional losses, which can propagate value throughout the production and postharvest phases.

Does Use of Atoxigenic Biocontrol Products to Mitigate Aflatoxin in Maize Increase Fumonisin Content in Grains?

In the tropics and subtropics, maize (Zea mays) and other crops are frequently contaminated with aflatoxins by Aspergillus flavus. Treatment of crops with atoxigenic isolates of A. flavus formulated into biocontrol products can significantly reduce aflatoxin contamination. Treated crops contain up to 100% fewer aflatoxins compared with untreated crops. However, there is the notion that protecting crops from aflatoxin contamination may result in increased accumulation of other toxins, particularly fumonisins produced by a few Fusarium species. The objective of this study was to determine if treatment of maize with aflatoxin biocontrol products increased fumonisin concentration and fumonisin-producing fungi in grains. Over 200 maize samples from fields treated with atoxigenic biocontrol products in Nigeria and Ghana were examined for fumonisin content and contrasted with maize from untreated fields. Apart from low aflatoxin levels, most treated maize also harbored fumonisin levels considered safe by the European Union (<1 part per million; ppm). Most untreated maize also harbored equally low fumonisin levels but contained higher aflatoxin levels. In addition, during one year, we detected considerably lower Fusarium spp. densities in treated maize than in untreated maize. Our results do not support the hypothesis that treating crops with atoxigenic isolates of A. flavus used in biocontrol formulations results in higher grain fumonisin levels.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

The Atoxigenic Biocontrol Product Aflasafe SN01 Is a Valuable Tool to Mitigate Aflatoxin Contamination of Both Maize and Groundnut Cultivated in Senegal

Aflatoxin contamination of groundnut and maize infected by Aspergillus section Flavi fungi is common throughout Senegal. The use of biocontrol products containing atoxigenic Aspergillus flavus strains to reduce crop aflatoxin content has been successful in several regions, but no such products are available in Senegal. The biocontrol product Aflasafe SN01 was developed for use in Senegal. The four active ingredients of Aflasafe SN01 are atoxigenic A. flavus genotypes native to Senegal and distinct from active ingredients used in other biocontrol products. Efficacy tests on groundnut and maize in farmers' fields were carried out in Senegal during the course of 5 years. Active ingredients were monitored with vegetative compatibility analyses. Significant (P < 0.05) displacement of aflatoxin producers occurred in all years, districts, and crops. In addition, crops from Aflasafe SN01-treated fields contained significantly (P < 0.05) fewer aflatoxins both at harvest and after storage. Most crops from treated fields contained aflatoxin concentrations permissible in both local and international markets. Results suggest that Aflasafe SN01 is an effective tool for aflatoxin mitigation in groundnut and maize. Large-scale use of Aflasafe SN01 should provide health, trade, and economic benefits for Senegal.[Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Knowledge, Attitude and Practice of Malawian Farmers on Pre- and Post-Harvest Crop Management to Mitigate Aflatoxin Contamination in Groundnut, Maize and Sorghum-Implication for Behavioral Change

A knowledge, attitude and practice (KAP) study was conducted in three districts of Malawi to test whether the training had resulted in increased knowledge and adoption of recommended pre- and post-harvest crop management practices, and their contribution to reducing aflatoxin contamination in groundnut, maize and sorghum. The study was conducted with 900 farmers at the baseline and 624 farmers at the end-line, while 726 and 696 harvested crop samples were collected for aflatoxin testing at the baseline and end-line, respectively. Results show that the knowledge and practice of pre- and post-harvest crop management for mitigating aflatoxin were inadequate among the farmers at the baseline but somewhat improved after the training as shown at the end-line. As a result, despite unfavorable weather, the mean aflatoxin contamination level in their grain samples decreased from 83.6 to 55.8 ppb (p < 0.001). However, it was also noted that increased knowledge did not significantly change farmers' attitude toward not consuming grade-outs because of economic incentive incompatibility, leaving potential for improving the practices further. This existing gap in the adoption of aflatoxin mitigation practices calls for approaches that take into account farmers' needs and incentives to attain sustainable behavioral change.

Assessment of aflatoxin B1-lysine adduct in serum of infant population of the Huasteca Potosina, México – a pilot study

Aflatoxins are mycotoxins considered to be highly toxic and produce adverse effects on human health. These compounds, mainly aflatoxin B1 (AFB1), have been classified as human carcinogens, due to its association with the development of hepatocellular carcinoma. In Mexico, the study of aflatoxins has been focused on the evaluation of products of the basic basket, particularly on maize, which is the basis of the Mexican diet. On the other hand, most of these studies have been conducted in urban areas. Indigenous populations may be exposed to a higher risk than urban ones due to the high consumption of tortillas, the harvest and the storage conditions of their food; hence, AFB1 is frequently found contaminating maize, which is the main food source for Mexicans. There is scarce evidence of exposure in vulnerable populations, such as children. Therefore, the main objective of this research was to conduct a pilot study for the evaluation of exposure to AFB1 through the AFB1-lys adduct in 31 serum samples of children from indigenous communities in Mexico. AFB1-lys was measured by High Pressure Liquid Chromatography with fluorescence detector (HPLC-FLD), with limits of detection and quantification of 3.5 and 4.7 pg/ml, respectively. Results from this pilot study revealed that 13% of children were of short stature, 9.7% presented overweight and 6.5% obesity. 45% of the children presented detectable concentrations of AFB1-lys adduct, with a median (minimum-maximum) of 5.6 (4.8-6.5) pg of AFB1-lys adduct/mg of albumin. The AFB1-lysine exposure biomarker is an important tool for the surveillance of aflatoxins and their effects on health, so, following this intervention, it would be necessary to monitor the exposure of vulnerable populations to aflatoxins, especially in rural areas where foods are more contaminated.

"Ground-Truthing" Efficacy of Biological Control for Aflatoxin Mitigation in Farmers' Fields in Nigeria: From Field Trials to Commercial Usage, a 10-Year Study

In sub-Saharan Africa (SSA), diverse fungi belonging to Aspergillus section Flavi frequently contaminate staple crops with aflatoxins. Aflatoxins negatively impact health, income, trade, food security, and development sectors. Aspergillus flavus is the most common causal agent of contamination. However, certain A. flavus genotypes do not produce aflatoxins (i.e., are atoxigenic). An aflatoxin biocontrol technology employing atoxigenic genotypes to limit crop contamination was developed in the United States. The technology was adapted and improved for use in maize and groundnut in SSA under the trademark Aflasafe. Nigeria was the first African nation for which an aflatoxin biocontrol product was developed. The current study includes tests to assess biocontrol performance across Nigeria over the past decade. The presented data on efficacy spans years in which a relatively small number of maize and groundnut fields (8-51 per year) were treated through use on circa 36,000 ha in commercially-produced maize in 2018. During the testing phase (2009-2012), fields treated during one year were not treated in the other years while during commercial usage (2013-2019), many fields were treated in multiple years. This is the first report of a large-scale, long-term efficacy study of any biocontrol product developed to date for a field crop. Most (>95%) of 213,406 tons of maize grains harvested from treated fields contained <20 ppb total aflatoxins, and a significant proportion (>90%) contained <4 ppb total aflatoxins. Grains from treated plots had preponderantly >80% less aflatoxin content than untreated crops. The frequency of the biocontrol active ingredient atoxigenic genotypes in grains from treated fields was significantly higher than in grains from control fields. A higher proportion of grains from treated fields met various aflatoxin standards compared to grains from untreated fields. Results indicate that efficacy of the biocontrol product in limiting aflatoxin contamination is stable regardless of environment and cropping system. In summary, the biocontrol technology allows farmers across Nigeria to produce safer crops for consumption and increases potential for access to premium markets that require aflatoxin-compliant crops.

Aflatoxin in Chili Peppers in Nigeria: Extent of Contamination and Control Using Atoxigenic Aspergillus flavus Genotypes as Biocontrol Agents

Across sub-Saharan Africa, chili peppers are fundamental ingredients of many traditional dishes. However, chili peppers may contain unsafe aflatoxin concentrations produced by Aspergillus section Flavi fungi. Aflatoxin levels were determined in chili peppers from three states in Nigeria. A total of 70 samples were collected from farmers’ stores and local markets. Over 25% of the samples contained unsafe aflatoxin concentrations. The chili peppers were associated with both aflatoxin producers and atoxigenic Aspergillus flavus genotypes. Efficacy of an atoxigenic biocontrol product, Aflasafe, registered in Nigeria for use on maize and groundnut, was tested for chili peppers grown in three states. Chili peppers treated with Aflasafe accumulated significantly less aflatoxins than nontreated chili peppers. The results suggest that Aflasafe is a valuable tool for the production of safe chili peppers. Use of Aflasafe in chili peppers could reduce human exposure to aflatoxins and increase chances to commercialize chili peppers in premium local and international markets. This is the first report of the efficacy of any atoxigenic biocontrol product for controlling aflatoxin in a spice crop.

Mitigating Aflatoxin Contamination in Groundnut through A Combination of Genetic Resistance and Post-Harvest Management Practices

Aflatoxin is considered a "hidden poison" due to its slow and adverse effect on various biological pathways in humans, particularly among children, in whom it leads to delayed development, stunted growth, liver damage, and liver cancer. Unfortunately, the unpredictable behavior of the fungus as well as climatic conditions pose serious challenges in precise phenotyping, genetic prediction and genetic improvement, leaving the complete onus of preventing aflatoxin contamination in crops on post-harvest management. Equipping popular crop varieties with genetic resistance to aflatoxin is key to effective lowering of infection in farmer's fields. A combination of genetic resistance for in vitro seed colonization (IVSC), pre-harvest aflatoxin contamination (PAC) and aflatoxin production together with pre- and post-harvest management may provide a sustainable solution to aflatoxin contamination. In this context, modern "omics" approaches, including next-generation genomics technologies, can provide improved and decisive information and genetic solutions. Preventing contamination will not only drastically boost the consumption and trade of the crops and products across nations/regions, but more importantly, stave off deleterious health problems among consumers across the globe.