Toxigenic potential of Aspergillus species occurring on maize kernels from two agro-ecological zones in Kenya.

Sheila Okoth,Erastus Kang'Ethe,Vincent Ayugi,Vesa Joutsjoki,Beatrice Nyongesa,Hannu Korhonen

doi:10.3390/toxins4110991

Sheila Okoth, Erastus Kang'Ethe + Show 4 more

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https://doi.org/10.3390/toxins4110991

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Journal: Toxins	Publication Date: Oct 25, 2012
Citations: 103	License type: CC BY 4.0

Affiliation: University of Nairobi, Agrifood Research Finland

Abstract

Two agro-ecological zones in Kenya were selected to compare the distribution in maize of Aspergillus spp. and their toxigenicity. These were Nandi County, which is the main maize growing region in the country but where no human aflatoxicoses have been reported, and Makueni County where most of the aflatoxicosis cases have occurred. Two hundred and fifty-five households were sampled in Nandi and 258 in Makueni, and Aspergillus was isolated from maize. Aspergillus flavus and A. parasiticus isolates were tested for the presence of aflD and aflQ genes. Positive strains were induced to produce aflatoxins on yeast extract sucrose and quantified using liquid chromatography-tandem mass spectrometry (LCMSMS). Aspergillus flavus was the most common contaminant, and the incidence of occurrence in Nandi and Makueni was not significantly different (82.33% and 73.26%, respectively). Toxigenic strains were more prevalent than non-toxigenic strains. All the toxigenic strains from Makueni were of the S-type while those from Nandi belonged to the L-type. Quantitative differences in aflatoxin production in vitro between isolates and between strains were detected with S strains producing relatively larger amounts of total aflatoxins, B toxins and lower values for G toxins. This was in accord with the frequent aflatoxicosis outbreaks in Makueni. However some L strains produced considerable amounts of B toxins. Given the widespread distribution of toxigenic strains in both regions, the risk of aflatoxin poisoning is high when favorable conditions for toxin production occur.

Highlights

Maize is a staple food crop in Kenya for both urban and rural areas with an estimated 1.6 million hectares under cultivation
Aspergillus was the most common fungus isolated from maize in both regions with over 60% incidence in all locations followed by Fusarium species and Penicillium
In Nandi, Aspergillus was predominant in Kaptumo while Fusarium and Penicillium was more common in maize from Kilibwoni

Summary

Introduction

Maize is a staple food crop in Kenya for both urban and rural areas with an estimated 1.6 million hectares under cultivation. It is grown by both small- and large-scale farmers. Several cases of aflatoxicosis have been reported in Kenya yearly since 1981 following consumption of maize contaminated with Aspergillus flavus and aflatoxins. In 2010 Kenya had about 2.3 million bags (estimated at $69 million) of maize contaminated with aflatoxins making it unfit for both human and livestock consumption and for trade, which was a loss to the small-scale farmers who depend on the crop for food and income [4]

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