Fumonisin contamination of maize (Zea mays) in aflatoxin ‘hot’ zones in eastern province of Kenya

Abstract

Natural Fusarium and fumonisin contamination were evaluated in 86 stored maize samples and correlated to damaged kernels (%). Maize samples were collected from selected farmers in Aflatoxin ‘hot’ zones of Eastern province. Samples were collected from Kitui and Kibwezi districts in May to June 2008. Fusarium species were isolated and identified using morphological characteristics at Mycology Laboratory, Kenya Medical Research Institute. Fumonisin
quantification was done using ELISA (RIDASCREEN ® ELISA test kit (Art. No.: R3401) at Bora Biotech, Nairobi.

Colony Forming Unit (CFU) counts indicated that apart from Aspergillus a common contaminant in maize, Fusarium species infestation was also high. The most common species being F. verticillioides isolated at (39.9 %) in the two districts. Other isolated Fusarium species included, F. proliferatum (15.1 %), F. solani (9.0 %), F. anthophilium (9.0 %), F. oxysporium (15.1 %), and F. Lateritium (12.1 %). Damaged kernels analysed in this study included insect infestation, mouldy kernels, and off coloured kernels. Results showed up to 20 % of the grains were damaged in some samples. Contamination with fumonisin toxin was observed to be high. Most of the samples exceeded 1 mg / kg the maximum tolerable levels recommended by the European commission. Fusarium species count and fumonisin levels showed positive correlation (p < 0.05). In addition, there was a positive correlation between damaged kernels (%) and Fusarium species count (p < 0.05). Positive correlation was also observed between damaged kernels (%) and Fusarium species count (p < 0.05). In general, F. verticillioides and F. proliferatum were isolated in samples with the highest percentage of kernel damage and highest fumonisin concentrations.

These findings indicate wide spread infestation and contamination of maize by Fusarium species and fumonisin toxins. It is apparent that apart from aflatoxins contamination there is also high level of fumonisin exposure in the high risk population necessitating urgent intervention measures to curb the long term health consequences in the population.

Keywords: Fusarium spp, Mycotoxin, Fumonisin, Zea maize, Aflatoxin ‘Hot’ zones