Correlation between Aspergillus flavus fungal biomass and aflatoxin contamination in harvested maize: insights from Kenya and Tanzania

Controlling the occurrence of aflatoxins in foods must be accompanied by managing the fungi responsible for their production. The abundance and diversity of aflatoxin-producing Aspergillus flavus are responsible for the accumulation of these toxins in crops, posing a persistent threat to public health and the economy in tropical developing countries. A study was conducted to investigate the occurrence and level of A. flavus and relate them to aflatoxin levels in maize in Kenya and Tanzania. A total of 786 maize samples were collected during harvesting in selected areas of the two countries for analysis. The fungal abundance in the samples was measured as the amount of fungal DNA relative to maize DNA. This was accomplished by quantifying the fungal DNA using qPCR, targeting the internal transcribed spacer (ITS) gene, while the maize DNA was quantified through the alpha-tubulin gene, the two genes known to be conserved. Aflatoxins were quantified using ultra-high performance liquid chromatography, coupled with ultra-high sensitivity, ultra-fast triple quadrupole tandem-mass spectrophotometer. A. flavus was detected in 88.5% of the 786 tested samples, and the average fungal load for these samples (expressed as the log host/pathogen ratio) was 5.53. Aflatoxin occurrence was positive in 31.9% of the samples, with an average level of 2.3 ± 0.643 ppb. The study established a positive relationship between the occurrence and level of aflatoxin B1 and the presence and biomass of A. flavus, which was statistically proven. These findings emphasize the need to place substantial attention on preharvest control of A. flavus in cereal fields as an effort to control the accumulation of aflatoxin B1 in foods.