Abstract
Dried insects and fish are important sources of income and dietary protein in Zambia. Some aflatoxin-producing fungi are entomopathogenic and also colonize insects and fish after harvest and processing. Aflatoxins are carcinogenic, immune-suppressing mycotoxins that are frequent food contaminants worldwide. Several species within Aspergillus section Flavi have been implicated as causal agents of aflatoxin contamination of crops in Africa. However, aflatoxin producers associated with dried fish and edible insects in Zambia remain unknown, and aflatoxin concentrations in these foods have been inadequately evaluated. The current study sought to address these data gaps to assess potential human vulnerability through the dried fish and edible insect routes of aflatoxin exposure. Caterpillars ( n = 97), termites ( n = 4), and dried fish ( n = 66) sampled in 2016 and 2017 were assayed for aflatoxin by using lateral flow immunochromatography. Average aflatoxin concentrations exceeded regulatory limits for Zambia (10 μg/kg) in the moth Gynanisa maja (11 μg/kg), the moth Gonimbrasia zambesina (Walker) (12 μg/kg), and the termite Macrotermes falciger (Gerstacker) (24 μg/kg). When samples were subjected to simulated poor storage, aflatoxins increased ( P < 0.001) to unsafe levels in caterpillars (mean, 4,800 μg/kg) and fish ( Oreochromis) (mean, 23 μg/kg). The L strain morphotype of A. flavus was the most common aflatoxin producer on dried fish (88% of Aspergillus section Flavi), termites (68%), and caterpillars (61%), with the exception of Gynanisa maja, for which A. parasiticus was the most common (44%). Dried fish and insects supported growth (mean, 1.3 × 109 CFU/g) and aflatoxin production (mean, 63,620 μg/kg) by previously characterized toxigenic Aspergillus section Flavi species, although the extent of growth and aflatoxigenicity depended on specific fungus-host combinations. The current study shows the need for proper storage and testing of dried insects and fish before consumption as measures to mitigate human exposure to aflatoxins through consumption in Zambia.
Highlights
Dried insects and fish are important sources of income and dietary protein in Zambia
Aflatoxins were detected in almost all fish and insects evaluated, with the termite M. falciger and the caterpillars Gynanisa maja and Gonimbrasia zambesina having average levels above those allowed for food in Zambia (Table 1)
Aflatoxin levels in caterpillars in the current study were different from those previously reported, where average aflatoxins in many locations exceeded 20 lg/kg [31]. These differences may result from differences in species examined, differences in environmental conditions to which the insects were subjected during processing and storage [8, 20], or differences in Aspergillus section Flavi community compositions [21, 34]
Summary
Dried insects and fish are important sources of income and dietary protein in Zambia. Several species within Aspergillus section Flavi have been implicated as causal agents of aflatoxin contamination of crops in Africa. Aflatoxin producers associated with dried fish and edible insects in Zambia remain unknown, and aflatoxin concentrations in these foods have been inadequately evaluated. The L strain morphotype of A. flavus was the most common aflatoxin producer on dried fish (88% of Aspergillus section Flavi), termites (68%), and caterpillars (61%), with the exception of Gynanisa maja, for which A. parasiticus was the most common (44%). Dried fish and insects supported growth (mean, 1.3 3 109 CFU/g) and aflatoxin production (mean, 63,620 lg/kg) by previously characterized toxigenic Aspergillus section Flavi species, the extent of growth and aflatoxigenicity depended on specific fungus-host combinations. Aspergillus species and genotypes vary in average aflatoxin-producing potential, and the relative importance of specific etiologic agents may vary among regions [9]. The current study sought to (i) quantify aflatoxins in insects and fish from markets in Zambia, (ii) characterize communities of Aspergillus section Flavi on insects and fish, and (iii) assess the capacity of insects and fish from Zambia to support growth and aflatoxin production by the observed Aspergillus section Flavi
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