Aflatoxin-Producing Fungi and Contamination in Zambia

Abstract

Aflatoxins are cancer-causing, immuno-suppressive mycotoxins that frequently contaminate important staples in Zambia including maize and groundnut. Managing aflatoxins begins with understanding the distribution of aflatoxins across the target region. Seventeen percent of crops from markets contained aflatoxin concentrations above allowable levels in Zambia, with the frequency of contamination in groundnut and maize highest in warmest regions of the country. Proper management of aflatoxin contamination requires a clear understanding of the etiologic agents of the observed contamination. Several species within Aspergillus section Flavi have been implicated as causal agents of aflatoxin contamination in Africa. In Zambia, A. parasiticus was the main etiologic agent of aflatoxin contamination of maize and groundnut, although fungi with S morphology also caused contamination. Aspergillus flavus L morphotype fungi were associated with reduced aflatoxins, suggesting natural biological control by atoxigenic strains may reduce aflatoxin contamination in Zambia. In addition to maize and groundnut, wild insects, fruits and fish are important sources of food and incomes in Zambia. Unfortunately, both insects and wild plants are susceptible to aflatoxin contamination. To evaluate the safety of wild insects and fruit, concentrations of aflatoxins and presence of aflatoxin-producers were assessed. Some species of wild fruits and insects were found to have unsafe levels of aflatoxins suggesting mitigation efforts should target these important foods of Zambia in addition to crops such as groundnut and maize. New lineages of aflatoxin-producing fungi have been described, and found associated with cases of aflatoxicoses in Kenya and elsewhere. Although A. parasiticus is highly frequent and an important etiologic agent of aflatoxin contamination, it is not known how this fungus is related to similar fungi elsewhere. A multigene phylogenetic analysis revealed at least two new groups divergent from known fungal species whose frequencies need to be modified if aflatoxin contamination of crops is to be reduced.