Rice grains can be attacked by a range of pathogens, including Aspergillus species, which can cause the accumulation of aflatoxins and represent a serious threat to the consumers. Aflatoxins are secondary metabolites synthesized by Aspergillus species and naturally occur in various foodstuffs. In this study, we sought to analyze the prevalence of aflatoxin-producing Aspergillus spp. in rice grains currently sold in Kenyan local markets. We analyzed a total of 98 samples randomly collected and primarily analyzed to observe moisture content and fungal growth. We then isolated Aspergillus species, characterized them morphologically and using the Internal transcribed spacer (ITS) primers. Finally, we screened them for aflatoxin-producing isolates targeting Norsolorinic Acid (nor-1) and Versicolorin (ver-1) specific genes involved in aflatoxin biosynthesis. We observed that all tested samples were contaminated. The highest prevalence of Aspergillus species and aflatoxigenic fungal species, had values of 66% and 36.4% for nor-1 and ver-1, respectively. In total, 66% of all isolates were confirmed to be aflatoxin producers. The occurrence of high contamination levels of Aspergillus species points to the possibility of production of aflatoxins in rice grains. This work provides a baseline for future studies on the occurrence of mycotoxigenic fungal species in rice grains being sold in local markets and strategies to control these aflatoxigenic strains at pre- and post-harvest levels.

Aflatoxigenic fungi are most common filamentous fungi that synthesis aflatoxins and represent the major fungal pathogens to agricultural products. Aflatoxins remain a major threat to global food security, these molecules could be resisted into food during processing and in additional may remain within the food chain. Aflatoxins are carcinogenic, hepatotoxic, mutagenic, teratogenic, can inhibit numerous metabolic systems and immunosuppressive properties.Studies of aflatoxigenic strains can help to enhance strategies control and prevent aflatoxigenic fungi contamination and aflatoxins production in foodstuffs. In this study, isolation of Aspergillus species was based on morphological characteristics including the mycelium growth pattern, color, and properties of fruiting bodies of the fungi. The innovated technique loop-mediated isothermal amplification assay was applied to amplify Norsolorinic Acid gene.The loop-mediated isothermal amplification have been optimized by combination of the rapidity, simplicity and specificity to detect the target genomic DNA in the reactions. The amplification curves monitored by Loopamp realtime Turbidi meter were analyzed in order to distinguish aflatoxigenic and non-aflatoxigenic strains.Overall, the results showed that the loop-mediated isothermal amplification method was effective in detecting aflatoxigenic strains with high specificity of 71.5 % and sensitivity under lower concentrations of DNA. In additional, it was faster than the conventional polymerase chain reaction. The loop-mediated isothermal amplification assay described in this study might be a promising tool for prediction potential threats by aflatoxigenic fungi and aflatoxins risk in food and commodities.

Aflatoxins are secondary metabolites produced by Aspergillus species distributed on three main sections of the genus namely section A. Flavi, section A. Ochraceorosei, and section A. Nidulantes. They are common contaminates of dietary staples worldwide, including cereals, oil seeds, nuts, spices, meats, dairy products, fruit juices, dried fruits, eggs, and feeds and foods derived from these products. Aflatoxins are unavoidable widespread natural contaminants of foodstuffs with serious impacts on food safety, health, agricultural and livestock productivity. Aflatoxin B1 is the analyte with the highest toxic significance and the most potent hepatocarcinogenic among other aflatoxins, and humans may get exposed to it at any stage of life. Dietary exposure to aflatoxins is a public health concern due to their carcinogenic, acute aflatoxicosis and chronic effects, immunosuppression properties, among others. This study focused on aflatoxin B1 in rice grains. Rice is important staple food consumed widely, and consists of a major part of the diets for half of the world population. In general, there have been few reports on the occurrence of the aflatoxin B1 in rice grains compared to other cereals in Africa. However, love the occurrence of the aflatoxin B1 levels compared to other crops, is of concern because of the high consumption of rice in several countries in Africa. This study assessed aflatoxin B1 in rice grains, occurrence, control, socioeconomic and health implications. We quantitatively determine the levels of aflatoxin B1 content using Enzyme Linked Immunosorbent Assay method. 43.1 % of examined samples were positive in which 15.9 % for local rice and 27.2 % of imported rice, respectively, and 11.3 % of examined samples are above the maximum limit of aflatoxin B1 in rice established by European Union. According to the manufacturer instructions, the limit of detection is 1 μg/kg (ppb) in cereals. The concentration of aflatoxin B1 in examined samples ranged from 0 μg/kg to 3.2 μg/kg. These results are indicative of exposure of the population to aflatoxin and possible health hazard. The procedure used in this study is suitable for detection of mycotoxins at a very low concentration.

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The magnitude of rice grain losses during storage is huge and warrants critical attention. We investigated the diversity of fungi and insect contamination related to losses of domestic and imported rice from local mills and markets, stored under room conditions for 10 weeks in Cameroon. The highest percentage discolored grain was on imported milled white rice (3.5%), 10 weeks after storage. In general, imported rice samples contained the highest fungal load with a proportion of 65.90% compared to 34.3% for domestic samples. Weight loss due to insect damage was up to 19.9% in white milled domestic rice.Among the 67 isolated fungi strains, the genus Aspergillus had the highest prevalence (63.8%). From all the samples, 877 insects were collected with 719 (81.9%) of Sitophilus. It is urgent to develop sustainable and affordable storage methods to limit insect and fungi infestation on rice in Cameroon.