Global health issues of aflatoxins in food and agriculture: challenges and opportunities

Updates on food and feed mycotoxin contamination and safety in Africa with special reference to Nigeria

Mycotoxin contamination of food and feed is a major concern in sub-Sahara African countries, particularly Nigeria. It represents a significant limit to health of human, livestock as well as the international trade. Aflatoxins, fumonisins, ochratoxin, zearalenone, deoxynivalenol and beauvericin are the major mycotoxins recognised in the aetiology of food safety challenges that precipitated countless number of diseases. In Nigeria, aflatoxins and fumonisin found in nearly all crops are the most common mycotoxins of economic and health importance such as sorghum, maize and groundnuts. Thus, consumption of food contaminated with mycotoxins are inevitable, hence the need for adequate regulation is necessary in these frontier economies as done in many developed economies to ensure food safety for human and animals. In low and middle-income countries, especially Nigeria, there is lack of awareness and sufficient information on the risk associated with consequent of mycotoxin contamination on wellbeing of human, animals health and the economy. It is based on the foregoing that this paper summarized the status of mycotoxin present in Nigerian food and feeds relative to the global regulatory standards. This aimed at preventing consuming mycotoxin contaminated food stuff while confronting its associated challenges. Suggestions on some possible control strategies to mitigate vending mycotoxin food and feeds were made.

Hepatoprotective effects of Lactobacillus plantarum 299v supplemented via drinking water against aflatoxin-induced liver damage

The aim of this study was to examine the impact of intake of a lactic acid bacterium, Lactobacillus plantarum 299v (Lp299v) on aflatoxin-induced hepatotoxicity in broilers. For this, broilers were intoxicated with dietary aflatoxins and simultaneously treated with live Lp299v in drinking water. One-day-old male broilers were divided into eight groups (n = 10/group) as follows. Aflatoxin groups fed basal diet contaminated with aflatoxins (200 or 2000 ppb). The probiotic groups received drinking water enriched with live (Lp299v) (10⁸ CFU/ml). A group of birds was given a commercial mycotoxin binder (2.5 g/kg feed). Control groups received basal diet without probiotic or aflatoxin binder. The growth performance was calculated for the entire period (0-42 days), and blood and liver specimens were processed for histology and determination of liver damage markers. Results showed extensive damage including bile duct hyperplasia, hepatocellular ballooning, and necrosis in chickens fed aflatoxin alone. However, liver lesions were limited to lobular inflammation and pyknosis in broilers treated with aflatoxins along with Lp299v. The histology of the liver tissues from the birds on aflatoxin-free diet + probiotic appeared to be normal when compared to the respective controls. Histopathological indices in different experimental groups were corroborated with the liver damage markers namely, serum ALT, AST, LD, and γ-GT. It is concluded that the improvement in the growth performance and prevention of aflatoxin-related liver lesions could be mainly assigned to the probiotic therapy for the entire period of breeding, although the aflatoxin-binding ability of the Lp299v in inactivation of aflatoxins cannot be ruled out.RESEARCH HIGHLIGHTS Aflatoxin-related liver damage progression was inhibited by probiotics in broilers.Aflatoxin inactivation by probiotics can be assessed by liver histopathology.Growth performance in broilers was improved following the intake of probiotics.

Occurrence and Seasonal Variations of Aflatoxin M1 in Milk from Punjab, Pakistan

The manifestation of aflatoxins in feed and food is a major issue in the world as its presence leads to some health problems. This study investigates the incidence of aflatoxin M₁ (AFM₁) contamination in raw milk samples which were collected from Punjab, Pakistan. The Cluster Random Sampling technique was used to collect 960 milk samples from five different regions, and samples were collected every month. The AFM₁ level in raw milk was analyzed by the ELISA technique. The findings demonstrate that 70% of samples exceeded the United States permissible maximum residue limits (MRL 0.50 µg/L), with an overall AFM₁ level that ranged from 0.3 to 1.0 µg/L. AFM₁ contamination varied with the season: The highest average contamination was detected in winter (0.875 µg/L), followed by autumn (0.751 µg/L), spring (0.654 µg/L), and summer (0.455 µg/L). The Eastern region exhibited the highest average AFM₁ contamination (0.705 µg/L). Milk samples from the Northern region were found to be widely contaminated, as 86.9% samples exceeded the US MRL, followed by the Eastern region, with 72.3% samples being contaminated with >0.5 µg/L AFM₁. The study indicated that the raw milk supply chain was heavily contaminated. Recommendations and remedial measures need to be developed by regulatory authorities to improve the raw milk quality.

A Polyphasic Approach Aids Early Detection of Potentially Toxigenic Aspergilli in Soil

Key chili and maize growing areas of Pakistan were selected for a focused baseline study of the levels of Aspergillus spp. Investigations were undertaken using a combination of molecular and culture-based techniques. Samples investigated included soil samples, one-year-old corn cobs, and fresh chili from selected locations. Aspergillus strains obtained from corn cobs were screened using coconut milk agar, resulting in one strain that was positive for aflatoxin production. Whole genome sequencing (WGS) with low coverage techniques were employed to screen the isolates for differences in the ribosomal RNA gene cluster and mitochondrial genome, with the aflatoxigenic strain proving to have a distinctive profile. Finally, strains were subjected to matrix-assisted laser-desorption and ionization time-of-flight mass spectrometry (MALDI-ToF-MS) in order to obtain a proteomic ‘fingerprint’ which was used to distinguish the aflatoxigenic strain from the other isolates. The next generation sequencing (NGS) study was broadened to incorporate metabarcoding with ITS rRNA for determining the microbial biodiversity of the soil samples and presumptive screening for the presence of aflatoxigenic strains. Using information gleaned from the WGS results, a putative aflatoxigenic operational taxonomic unit (OTU) was observed in four of the 15 soil samples screened by metabarcoding. This method may have beneficial applications in early detection and surveillance programs in agricultural soils and commodities.

Socioeconomic Characteristics Influencing Level of Awareness of Aflatoxin Contamination of Feeds among Livestock Farmers in Meru District of Tanzania

Aflatoxins occurrence in feeds challenges human and animal health. Farmers' awareness status of these toxins has an effect on their level of exposure. The study assessed the influence of socioeconomic characteristics of farmers on their awareness of aflatoxin contamination of feeds. Data were collected from 258 households and analysed by SPSS program for descriptive statistics and association between socioeconomic characteristics and awareness of aflatoxin contamination of feeds. Over seventy percent of the farmers had never heard about aflatoxins. Education level, specialization, and period of keeping animals had significant influence on aflatoxin awareness. Hearing about aflatoxins was six times higher among farmers who studied life or social sciences than those without specialization and those who studied other fields. Awareness that aflatoxins may occur in feeds was twice higher among farmers with higher education than those with lower education. Perception that aflatoxins in feeds are detoxifiable was threefold higher among young people (with ≤10-year period of keeping animals) than among older ones. Awareness of aflatoxins was particularly low among farmers with low education and those without exposure to life or social sciences and vice versa. Sensitization is recommended to raise farmers' awareness on aflatoxin contamination of feeds and incorporating aflatoxin knowledge in school curricula.

The Stress Response Regulator AflSkn7 Influences Morphological Development, Stress Response, and Pathogenicity in the Fungus Aspergillus flavus

This study focused on AflSkn7, which is a stress response regulator in the aflatoxin-producing Aspergillus flavus. The ΔAflSkn7 mutants exhibited partially defective conidial formation and a complete inability to generate sclerotia, indicating AflSkn7 affects A. flavus asexual and sexual development. The mutants tolerated osmotic stress but were partially susceptible to the effects of cell wall stress. Additionally, the ΔAflSkn7 mutants were especially sensitive to oxidative stress. These observations confirmed that AflSkn7 influences oxidative stress responses rather than osmotic stress responses. Additionally, AflSkn7 was observed to increase aflatoxin biosynthesis and seed infection rates. These results indicate AflSkn7 affects A. flavus morphological development, stress response, aflatoxin production, and pathogenicity. The results of this study may facilitate the development of new methods to manage A. flavus infections.

Biotechnological advances for combating Aspergillus flavus and aflatoxin contamination in crops

Aflatoxins are toxic, carcinogenic, mutagenic, teratogenic and immunosuppressive byproducts of Aspergillus spp. that contaminate a wide range of crops such as maize, peanut, and cotton. Aflatoxin not only affects crop production but renders the produce unfit for consumption and harmful to human and livestock health, with stringent threshold limits of acceptability. In many crops, breeding for resistance is not a reliable option because of the limited availability of genotypes with durable resistance to Aspergillus. Understanding the fungal/crop/environment interactions involved in aflatoxin contamination is therefore essential in designing measures for its prevention and control. For a sustainable solution to aflatoxin contamination, research must be focused on identifying and improving knowledge of host-plant resistance factors to aflatoxin accumulation. Current advances in genetic transformation, proteomics, RNAi technology, and marker-assisted selection offer great potential in minimizing pre-harvest aflatoxin contamination in cultivated crop species. Moreover, developing effective phenotyping strategies for transgenic as well as precision breeding of resistance genes into commercial varieties is critical. While appropriate storage practices can generally minimize post-harvest aflatoxin contamination in crops, the use of biotechnology to interrupt the probability of pre-harvest infection and contamination has the potential to provide sustainable solution.

Inhibitory effect of eugenol on aflatoxin B1 production in Aspergillus parasiticus by downregulating the expression of major genes in the toxin biosynthetic pathway

Aflatoxin contamination of grains and agro-products is a serious food safety issue and a significant economic concern worldwide. In the present study, the effects of eugenol on Aspergillus parasiticus growth and aflatoxin production were studied in relation to the expression of some essential genes involved in aflatoxin biosynthetic pathway. The fungus was cultured in presence of serial two-fold concentrations of eugenol (15.62-500 μg mL(-1)) for 3 days at 28 °C. Mycelia dry weight was determined as an index of fungal growth, while aflatoxin production was assessed by high performance liquid chromatography. The expression of aflatoxin biosynthetic genes including ver-1, nor-1, pksA, omtA and aflR were evaluated by real-time PCR. Eugenol strongly inhibited A. parasiticus growth in the range of 19.16-95.83 % in a dose-dependent manner. Aflatoxin B1 production was also inhibited by the compound in the range of 15.07-98.0 %. The expressions of ver-1, nor-1, pksA, omtA and aflR genes were significantly suppressed by eugenol at concentrations of 62.5 and 125 μg mL(-1). These results indicate that eugenol may be considered as a good candidate to control toxigenic fungal growth and the subsequent contamination of food, feed and agricultural commodities by carcinogenic aflatoxins.