The effects of aflatoxin exposure on Hepatitis B-vaccine induced immunity in Kenyan children.

BACKGROUND: Globally, approximately three million children die each year from vaccine preventable infectious diseases mainly in developing countries. Despite the success of the expanded immunization program, not all infants and children around the world develop the same protective immune response to the same vaccine. A vaccine must induce a response over the basal immune response that may be driven by population-specific, environmental or socio-economic factors. Mycotoxins like aflatoxins are immune suppressants that are confirmed to interfere with both cell-mediated and acquired immunity. The mechanism of aflatoxin toxicity is through the binding of the bio-activated AFB1-8, 9-epoxide to cellular macromolecules. METHODS: We studied Hepatitis B surface antibodies [anti-HBs] levels to explore the immune modulation effects of dietary exposure to aflatoxins in children aged between one and fourteen years in Kenya. Hepatitis B vaccine was introduced for routine administration for Kenyan infants in November 2001. To assess the effects of aflatoxin on immunogenicity of childhood vaccines Aflatoxin B1-lysine in blood serum samples were determined using High Performance Liquid Chromatography with Fluorescence detection while anti-HBs were measured using Bio-ELISA anti-HBs kit. RESULTS: The mean ± SD of AFB1-lysine adducts in our study population was 45.38 ± 87.03 pg/mg of albumin while the geometric mean was 20.40 pg/mg. The distribution of AFB1-lysine adducts was skewed to the right. Only 98/205 (47.8%) of the study population tested positive for Hepatitis B surface antibodies. From regression analysis, we noted that for every unit rise in serum aflatoxin level, anti-HBs dropped by 0.91 mIU/ml (-0.9110038; 95% C.I -1.604948, -0.21706). CONCLUSION: Despite high coverage of routine immunization, less than half of the study population had developed immunity to HepB. Exposure to aflatoxin was high and weakly associated with low anti-HBs antibodies. These findings highlight a potentially significant role for environmental factors that may contribute to vaccine effectiveness warranting further research.

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

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.

Prevalence and factors associated with aflatoxin contamination of peanuts from Western Kenya.

Aflatoxin contamination of peanuts poses a risk to human health and has been identified as a major constraint to trade in eastern Africa. A survey was carried out to obtain baseline data on levels of aflatoxin in peanuts from major production regions in western Kenya. A total of 384 and 385 samples from Busia and Homabay districts, respectively, were obtained and analyzed for aflatoxin content with an indirect competitive ELISA protocol. Levels of aflatoxin ranged from 0 to 2688 and 7525 microg/kg in samples from Busia and Homa Bay, respectively. Of 769 samples, 87.01% contained <4 microg/kg of aflatoxin, 5.45% were in the range > or =4 and 20 microg/kg, while 7.54% exceeded the Kenya's regulatory limit of 20 microg/kg. There was a highly significant (chi(2)=14.17; P<0.0002) association between district of origin and sample aflatoxin levels. This observation was supported by a significant (chi(2)=11.98; P=0.0005) association between levels of aflatoxin and agro ecological zones. Only 3.26% of the samples from the dryer LM3 zone had >20 microg/kg compared with 10.28% of the samples from the wetter and humid LM1 zone. There was also a highly significant (chi(2)=9.73; P=0.0018) association between cultivar improvement status and aflatoxin levels. Logistic regression analysis revealed that the odds for peanuts from Busia being contaminated were 2.6 times greater than those for peanuts from Homabay. Planting improved cultivars would lower the odds of contamination to a half (odds ratio=0.552) those for local landraces. These results are discussed in relation to the risk of human exposure to aflatoxins and the need for proper sampling procedures for regulatory purposes.