Prevalence and mitigation of aflatoxins in Kenya (1960-to date)

Abstract

Aflatoxins are highly toxic metabolites of several Aspergillus species widely distributed throughout the environment. These toxins have adverse effects on humans and livestock at a few micrograms per kilogram (μg/kg) concentrations. Strict regulations on the concentrations of aflatoxins allowed in food and feed exist in many nations in the developing world. Loopholes in implementing regulations result in the consumption of dangerous concentrations of aflatoxins. In Kenya, where ‘farm-to-mouth’ crops become severely contaminated, solutions to the aflatoxins problem are needed. Across the decades, aflatoxins have repeatedly caused loss of human and animal life. A prerequisite to developing viable solutions for managing aflatoxins is understanding the geographical distribution and severity of food and feed contamination, and the impact on lives. This review discusses the scope of the aflatoxins problem and management efforts by various players in Kenya. Economic drivers likely to influence the choice of aflatoxins management options include historical adverse health effects on humans and animals, cost of intervention for mitigation of aflatoxins, knowledge about aflatoxins and their impact, incentives for aflatoxins safe food and intended scope of use of interventions. It also highlights knowledge gaps that can direct future management efforts. These include: sparse documented information on human exposure; few robust tools to accurately measure economic impact in widely unstructured value chains; lack of long-term impact studies on benefits of aflatoxins mitigation; inadequate sampling mechanisms in smallholder farms and grain holding stores/containers; overlooking social learning networks in technology uptake and lack of in-depth studies on an array of aflatoxins control measures followed in households. The review proposes improved linkages between agriculture, nutrition and health sectors to address aflatoxins contamination better. Sustained public awareness at all levels, capacity building and aflatoxins related policies are necessary to support management initiatives.

Aflatoxins: Production, Structure, Health Issues and Incidence in Southeast Asian and Sub-Saharan African Countries

“…The probable daily intake (PDI) of aflatoxin B1 in the country, via maize only, was recently estimated to vary between 0.07-60,612.00 ng/kg bw/day, with an average of 312.4 ng/kg bw/day) [80], which is alarming compared with an average of 10 to 200 ng/kg/day for the rest of the world [81], and with the conservative tolerable daily intake (TDI) of 0.11 to 0.19 ng/kg bw/day [82]. Incidentally, this country also ranks among the countries with the highest prevalence of oesophageal cancer, which was associated with aflatoxin intake as a risk factor [18,80,83]. Conversely, a recent survey on aflatoxin contamination of maize grown in eight different AEZs in Uganda revealed that the highest levels (a maximum of 3760 g/kg) and an average of 66.5 g/kg) were recorded in the zones with high rainfalls (1200->1400 mm); the percentage of samples exceeding the national regulatory standards of 10 g/kg reached 22.2% [84].…”

“…Subsequently, Wicklow and Shotwell [16] confirmed the production of B and G aflatoxins by other strains of A. flavus; NRRL strains 3357, 6412, 6554, 6555, and 13003. Yet, the inability of A. flavus to produce the G aflatoxins was later reiterated and evidenced by genetic analysis relating indel (short insertions or deletions) mutations in the cypA/norB region in A. flavus to the impairment of the expression of genes coding for P450 monooxygenase enzyme required for the biosynthesis of G aflatoxins [17][18][19]. However, it was argued that this mutation does not occur in all strains, and some A. flavus strains can still produce B or G aflatoxins depending on the morphotype (S or L) and on the phylogenetic group (I or II) to which they belong.…”

“…This was explained by the fact that the production of aflatoxins increases as the size of sclerotia decreases during their formation [22]. Indeed, in the low-elevation regions in Kenya where the S-morphotype is predominating (>90%), the concentration of aflatoxin B1 in maize was reported to exceed 1000 g/kg [18]. This was practically illustrated by the higher incidence of deadly acute aflatoxicosis in these regions compared with those where the S-morphotype strains are less common [23].…”

“…The levels of aflatoxins in a product within the same AEZ were shown to vary greatly depending on the rainfall and temperature variations from one year to another, in addition to the experimental design and the sampling point [96]. In fact, there is a multiplicity of factors that interfere with the effect of the climate type at different production stages from plant development to crop storage [18,62]. It is increasingly recognized that management systems with rigorous implementation of the good agricultural practices (GAPs) and farmer trainings are critical measures to mitigate the incidence of aflatoxins in agricultural products regardless of the climate type [18,67,80,[97][98][99].…”

“…In fact, there is a multiplicity of factors that interfere with the effect of the climate type at different production stages from plant development to crop storage [18,62]. It is increasingly recognized that management systems with rigorous implementation of the good agricultural practices (GAPs) and farmer trainings are critical measures to mitigate the incidence of aflatoxins in agricultural products regardless of the climate type [18,67,80,[97][98][99]. The implementation of such measures in South Africa in the framework of a project on the "Adaptation of agricultural practices to climate change in Sub-Saharan Africa (CAADP)" aimed at "good agricultural adaptation practices" [100], appears to have been successful in controlling aflatoxin contamination.…”