Prevalence of Aflatoxins in Wheat and Maize Grain Plant-Pest-Pathways at Three Zimbabwean Ports of Entries

The presence of aflatoxin producing fungi in food imports necessitates rigorous screening. A total of 42 maize and wheat pest pathways found contaminated with aflatoxins-causing- fungi; (<i>Aspergillus flavus and A. parasiticus)</i> during 2023-2024 phytosanitary inspections at three Zimbabwe ports of entries were subjected to aflatoxin screening at the Fertilizers, Farm Feeds and Remedies Institute (FFRI) using semi-quantitative Best Food Method (BFD) by means of Thin Layer Chromatograph (TLC) to detect aflatoxins contamination. Standard reference mixes containing aflatoxins concentration of 0.5 μg/kg each for B<sub>1</sub> and B<sub>2</sub>, and 0.25 μg/kg each for G<sub>1</sub> and G<sub>2</sub> were checks. Controls with known concentration of aflatoxins B<sub>1</sub>, B<sub>2</sub>, G<sub>1</sub> and G<sub>2</sub> were visibly seen under Ultra Violet (UV) light read at 365 nm and differences of spots intensity for B<sub>1</sub> and B<sub>2</sub> aflatoxins concentration of 12 μg/kg, 24 μg/kg and 36 μg/kg and G<sub>1</sub> and G<sub>2</sub> aflatoxins concentration 6 μg/kg, 12 μg/kg and 18 μg/kg were noted. However, despite the presence of aflatoxin causing fungi in the 42 samples tested, aflatoxins were not detected by the TLC which has a detection limit of <1ppb. Spearman’s rho correlation matrix showed perfectly (ρ = 1.000, p < 0.01) or near-perfectly correlation (ρ ≥ 0.999, p < 0.001) on the four aflatoxin groups (B<sub>1</sub>, B<sub>2</sub>, G<sub>1</sub>, G<sub>2</sub>). Perfect correlations were revealed between aflatoxins B<sub>1</sub> and B<sub>2</sub> and between aflatoxins G<sub>1</sub> and G<sub>2</sub> whilst extremely strong correlations were revealed between aflatoxins B<sub>1</sub> and G<sub>1</sub>; B<sub>1</sub> and G<sub>2</sub>; B<sub>2</sub> and G<sub>1</sub> and B<sub>2</sub> and G<sub>2</sub>. The test was highly significant (p<0.001) suggesting strong indication of no association between the four aflatoxin categories. Chi-Square goodness of test revealed statistically significant deviations from the expected frequencies (χ² (4) = 154.083, <i>p</i> < 0.001) suggesting that observed distributions of the aflatoxin were not caused by random variation. Due to the risks of mycotoxin co-occurrences in cereals, the research recommends expanding the testing beyond aflatoxins to include fumonisins caused by <i>Fusarium</i> species and other mycotoxins associated with <i>Penicillum </i>sp and <i>Macrophomina phaseolin </i>as these pests were also isolated from the cross border cereal grain-pest-pathways entering Zimbabwe. This research was limited by non-testing of the isolated fungi on their potential to cause aflatoxins contamination.