Market samples as a source of chronic aflatoxin exposure in Kenya

Surveillance of food and feed quality in Kenya has not reached effective level due to the expensive procedures of mycotoxin analysis and poor structures in quality control. Most foodstuffs and feeds sold in local markets do not go through any quality control measures. The outbreaks of aflatoxicoses every year since the major outbreak that occurred in 2004 (CDC, 2004; Muture and Ogana, 2005, Azziz-Baumgartner et al., 2005) suggests that the population is exposed to aflatoxins in their diet. Chronic exposure could be a more serious problem than the outbreaks of aflatoxicosis that attract attention at the time they occur. This paper analyses the extent to which market food and feed samples expose the residents of urban Nairobi Province to aflatoxins. Using TLC method of aflatoxins analysis, maize for food and feed samples collected randomly as part of routine surveillance between the years 2006-2009 were tested. Only 17% of the total maize sampled and 5% of feed were fit for human and animal consumption respectively. Maize Grain Grade 11 and maize milled products were significantly highly contaminated compared with Maize Grain Grade 1 throughout the period of sampling. There was no significant difference in level of contamination among the feeds tested

Aflatoxin Binders in Foods for Human Consumption-Can This be Promoted Safely and Ethically?

Aflatoxins continue to be a food safety problem globally, especially in developing regions. A significant amount of effort and resources have been invested in an attempt to control aflatoxins. However, these efforts have not substantially decreased the prevalence nor the dietary exposure to aflatoxins in developing countries. One approach to aflatoxin control is the use of binding agents in foods, and lactic acid bacteria (LAB) have been studied extensively for this purpose. However, when assessing the results comprehensively and reviewing the practicality and ethics of use, risks are evident, and concerns arise. In conclusion, our review suggests that there are too many issues with using LAB for aflatoxin binding for it to be safely promoted. Arguably, using binders in human food might even worsen food safety in the longer term.Peer reviewe

Characterization of Pathogenic Fungi Infecting Citrullus lanatus in Different Agroecological Regions of Embu County, Kenya

Watermelon (Citrullus lanatus) fruit is nutritious and a profitable cash crop. Its production in Kenya however has dropped from 379.36K metric tonnes to 173.70K metric tonnes in the last five years; attributed to pests, diseases and unpredictable climatic conditions. Study done between July and November, 2018 isolated and characterized fungi associated with watermelon determining their diversity and occurence frequency in Embu County, Kenya. Necrotic fruits and leaves (n=160) were sampled from random farms (n=16). Fungi isolated and  cultured on PDA.; characterized by morphological and molecular method. ANOVA was used to detect fungal prevalence differences among sites. Fusarium oxysporum was most prevelent with 73% frequency, Aspergillus niger (32%). Penicilliun crustosum and Fusarium brachygibbosum at 31%  each. Least prevalent was Trichoderma asperellum (1%). Significant differences (F= 23.365, p=0.05, df=13), were observed among agroecological sites except for Fusarium oxysporium and F. brachygibbosum. Majority of fungi identified were of significant economic importance

Biocontrol of Aspergillus and Fusarium Mycotoxins in Africa : benefits and limitations

Fungal contamination and the consequent mycotoxin production is a hindrance to food and feed safety, international trade and human and animal health. In Africa, fungal contamination by Fusarium and Aspergillus is heightened by tropical climatic conditions that create a suitable environment for pre- and postharvest mycotoxin production. The biocontrol of Fusarium and its associated fusariotoxins has stagnated at laboratory and experimental levels with species of Trichoderma, Bacillus and atoxigenic Fusarium being tested as the most promising candidates. Hitherto, there is no impetus to upscale for field use owing to the inconsistent results of these agents. Non-aflatoxigenic strains of Aspergillus have been developed to create biocontrol formulations by outcompeting the aflatoxigenic strains, thus thwarting aflatoxins on the target produce by 70% to 90%. Questions have been raised on their ability to produce other mycotoxins like cyclopiazonic acid, to potentially exchange genetic material and to become aflatoxigenic with consequent deleterious effects on other organisms and environments. Other biocontrol approaches to mitigate aflatoxins include the use of lactic acid bacteria and yeast species which have demonstrated the ability to prevent the growth of Aspergillus flavus and consequent toxin production under laboratory conditions. Nevertheless, these strategies seem to be ineffective under field conditions. The efficacy of biological agents is normally dependent on environmental factors, formulations' safety to non-target hosts and the ecological impact. Biocontrol agents can only be effectively evaluated after long-term use, causing a never-ending debate on the use of live organisms as a remedy to pests and diseases over the use of chemicals. Biocontrol should be used in conjunction with good agricultural practices coupled with good postharvest management to significantly reduce mycotoxins in the African continent

Cultural Characterization of Fungi Isolated From Oil Contaminated Soils

Application of Fungi for effective removal of hydrocarbon contamination from soil is being considered as the better option when it comes to biodegradation. Other method like physical and chemical bioremediation leads to production of toxic compounds and these methods are not cost effective. In the present study, soil samples from four different oil contaminated soils were assessed for any recovery of fungi present. Cultural characterization was used as preliminary identification using keys.  Initial isolation from the oil contaminated soil was done using potato dextrose agar.  Colonies were observed and characterized morphologically. The isolates were grown at varied temperatures and pH. Eight fungal isolates were recovered from polluted soils namely, Trichoderma viride, Trichoderma spirale, Neosartorya pseudofischeri, Neosartorya aureola, Aspergillus flavus, Aspergillus terreus, Penicillium griseofulvum and Trichoderma longibrachiatum.  The optimum growth temperature range for the eight fungi was 30oC and 40oC.  There was no growth at 50oC for all isolates except some slight growth by Aspergillus flavus.  Optimum growth at pH 7 and pH 9 and poor growth at pH 5 was noted. This study will contribute to the database on locally available fungal diversity and their ecology. Keywords.  Fungi, Bioremediation, oil contamination, biodegradatio

Preharvest Management Strategies and Their Impact on Mycotoxigenic Fungi and Associated Mycotoxins

Mycotoxigenic fungi that contaminate grain crops can lead to reduced grain quality, crop yield reduction and mycotoxicosis among humans and livestock. Preharvest management of fungi and mycotoxin contamination is considered among the most important mitigating strategies. Approaches include the breeding of resistant cultivars, use of microorganisms chemical control, production practises and the management of plant stressors. Resistant plants provide an effective and environmentally sound strategy to control mycotoxigenic fungi and mycotoxins; and have been documented. Their incorporation into commercial cultivars is, however, slow and complex. Therefore, emphasis should be placed on determining the resistance of cultivars and landraces currently used by producers. Chemical control has been successfully used for wheat; yet little to no research has been done on other important crops. Biological control strategies have focussed on Aspergillus flavus that produces aflatoxins and infects commercially important crops like maize and groundnuts. Commercial biological control products have been developed and field-tested in several African countries with promising results. The impacts of production practises are unclear under variable environmental conditions; but subsequent disease manifestation and mycotoxin contamination can be reduced. Each preharvest approaches contribute to managing mycotoxigenic fungi and their mycotoxins but integrating approaches may provide more effective management of fungal and mycotoxin contamination in crops

Effects of Medicinal Plant Extracts and Photosensitization on Aflatoxin Producing Aspergillus flavus

This study was undertaken with an aim of exploring the effectiveness of medicinal plant extracts in the control of aflatoxin production. Antifungal properties, photosensitization, and phytochemical composition of aqueous and organic extracts of fruits from Solanum aculeastrum, bark from Syzygium cordatum, and leaves from Prunus africana, Ocimum lamiifolium, Lippia kituiensis, and Spinacia oleracea were tested. Spores from four-day-old cultures of previously identified toxigenic fungi, UONV017 and UONV003, were used. Disc diffusion and broth dilution methods were used to test the antifungal activity. The spores were suspended in 2 ml of each extract separately and treated with visible light (420 nm) for varying periods. Organic extracts displayed species and concentration dependent antifungal activity. Solanum aculeastrum had the highest zones of inhibition diameters in both strains: UONV017 (mean = 18.50±0.71 mm) and UONV003 (mean = 11.92±0.94 mm) at 600 mg/ml. Aqueous extracts had no antifungal activity because all diameters were below 8 mm. Solanum aculeastrum had the lowest minimum inhibitory concentration at 25 mg/ml against A. flavus UONV017. All the plant extracts in combination with light reduced the viability of fungal conidia compared with the controls without light, without extracts, and without both extracts and light. Six bioactive compounds were analyzed in the plant extracts. Medicinal plant extracts in this study can control conidia viability and hence with further development can control toxigenic fungal spread

Aflatoxin and the agriculture – nutrition nexus in Africa

Aflatoxins are a silent threat to health on the African continent. They are a group of mycotoxins – poisonous chemicals produced by fungi on crops that they colonise. Fatal in large amounts, in smaller concentrations aflatoxins harm humans, animals, birds and fish. The fungi that produce aflatoxins infect many of the cereals, legumes, oilseeds, roots, tubers, spices and nuts which are widely grown and eaten in Africa, placing aflatoxins at the very crux of the agriculture-nutrition nexus. This Technical Brief gives recommendations to fight against aflatoxins

Awareness and prevalence of mycotoxin contamination in selected Nigerian fermented foods

Fermented food samples (n = 191) including maize gruel (ogi), sorghum gruel (ogi-baba), melon seed (ogiri), locust bean (iru) and African oil bean seed (ugba) from Southwest Nigeria were quantified for 23 mycotoxins, including aflatoxin B-1 (AFB(1)), fumonisin B-1 (FB1), and sterigmatocystin (STE) using liquid chromatography-tandem mass spectrometry. The practices, perceived understanding and health risks related to fungal and mycotoxin contamination amongst fermented food sellers was also established. Data obtained revealed that 82% of the samples had mycotoxins occurring singly or in combination. FB1 was present in 83% of ogi-baba samples, whereas 20% of ugba samples contained AFB(1) (range: 3 to 36 mu g/kg) and STE was present in 29% of the ogi samples. In terms of multi-mycotoxin contamination, FB1 + FB2 + FB3 + STE + AFB(1) + alternariol + HT-2 co-occurred within one sample. The awareness study revealed that 98% of respondents were unaware of mycotoxin contamination, and their education level slightly correlated with their level of awareness (p < 0.01, r = 0.308). The extent to which the analyzed mycotoxins contaminated these food commodities, coupled with the poor perception of the population under study on fungi and mycotoxins, justifies the need to enact fungal and mycotoxin mitigation strategies along the food chain

Curcumin-based photosensitization inactivates Aspergillus flavus and reduces aflatoxin B1 in maize kernels

Different methods have been applied in controlling contamination of foods and feeds by the carcinogenic fungal toxin, aflatoxin, but nevertheless the problem remains pervasive in developing countries. Curcumin is a natural polyphenolic compound from the spice turmeric (Curcuma longa L.) that has been identified as an efficient photosensitiser for inactivation of Aspergillus flavus conidia. Curcumin mediated photoinactivation of A. flavus has revealed the potential of this technology to be an effective method for reducing population density of the aflatoxin-producing fungus in foods. This study demonstrates the influence of pH and temperature on efficiency of photoinactivation of the fungus and how treating spore-contaminated maize kernels affects aflatoxin production. The results show the efficiency of curcumin mediated photoinactivation of fungal conidia and hyphae were not affected by temperatures between 15 and 35 °C or pH range of 1.5–9.0. The production of aflatoxin B was significantly lower (p < 0.05), with an average of 82.4 μg/kg as compared to up to 305.9 μg/kg observed in untreated maize kept under similar conditions. The results of this study indicate that curcumin mediated photosensitization can potentially be applied under simple environmental conditions to achieve significant reduction of post-harvest contamination of aflatoxin B in maize