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Aflatoxin exposure, malaria and hepatitis B infection in rural Gambian children
S J Allen1, C P Wild, J G Wheeler
1Medical Research Council Laboratories, Fajara, The Gambia.
Insights
Gambian children show high aflatoxin exposure, with levels varying seasonally and between individuals. This exposure was linked to Hepatitis B infection and malaria but did not consistently affect immune responses or malaria outcomes.
Area of Science:
- Environmental Health
- Toxicology
- Infectious Disease Epidemiology
Background:
- Aflatoxins are toxic secondary metabolites produced by fungi, posing a significant health risk, particularly in regions with high consumption of contaminated food staples.
- Assessing aflatoxin exposure in vulnerable populations like children is crucial for understanding its health impacts.
- Hepatitis B virus (HBV) infection and malaria are prevalent in The Gambia, and potential interactions with environmental toxins like aflatoxins warrant investigation.
Purpose of the Study:
- To measure aflatoxin-albumin adduct levels in Gambian children as a biomarker of exposure.
- To investigate the relationships between aflatoxin exposure and malaria prevalence, immune responses to malaria antigens, and Hepatitis B surface antigen (HBsAg) carriage.
- To evaluate the impact of seasonal variations on aflatoxin exposure levels.
Main Methods:
- Serum samples were collected from Gambian children during the dry and rainy seasons.
- Aflatoxin-albumin adduct levels were quantified using established assays.
- Associations between adduct levels and malaria status, immune responses (humoral and cellular), and HBsAg carriage were analyzed.
- Seasonal variations and individual fluctuations in adduct levels were assessed.
Main Results:
- Nearly all serum samples showed detectable aflatoxin-albumin adducts, with generally high levels observed during the dry season.
- Higher adduct levels were found in Wollof children and varied significantly between villages.
- Aflatoxin-albumin adduct levels were elevated in HBsAg-positive children and those with Plasmodium falciparum parasitaemia.
- No consistent effect of aflatoxin exposure on malaria-specific antibody responses, lymphoproliferative responses, or subsequent malaria morbidity was observed.
- Significantly lower adduct levels were detected in the rainy season, with poor correlation between dry and rainy season levels in individuals.
Conclusions:
- Gambian children experience substantial aflatoxin exposure, characterized by significant seasonal variation and individual fluctuations.
- While aflatoxin exposure is associated with HBsAg positivity and malaria parasitaemia, its impact on immune responses and clinical outcomes related to malaria appears inconsistent.
- The dynamic nature of aflatoxin exposure necessitates careful consideration of seasonal variations and temporal fluctuations when designing future epidemiological studies using aflatoxin-albumin adducts as a biomarker.
Abstract:
Aflatoxin-albumin adduct levels were measured in serum samples obtained from a group of Gambian children. The relationships between exposure to aflatoxin and the prevalence of malaria, between exposure and humoral and cellular responses in vitro to defined malaria antigens and, amongst children with evidence of exposure to hepatitis B infection, between aflatoxin and carriage of the hepatitis B surface antigen (HBsAg), were assessed. Aflatoxin-albumin adduct was found in nearly all serum samples collected during a survey performed at the end of the dry season and levels of adduct were generally high (up to 720 pg aflatoxin-lysine equivalent/mg albumin). Higher levels of aflatoxin-albumin adduct were detected in Wollof children than in children of other ethnic groups and marked variation in mean adduct levels between villages was observed. Aflatoxin-albumin adduct levels were higher in children who were HbsAg positive and in children with Plasmodium falciparum parasitaemia than in controls. However, levels of adduct had no consistent effect on either malaria-specific antibody responses, lymphoproliferative responses in vitro, or morbidity from malaria during the subsequent rainy season. Much lower levels of aflatoxin-albumin adduct were detected in repeat samples obtained at the end of the rainy season. There was poor correlation between dry and rainy season levels of adduct in individual children. We have shown that Gambian children are exposed to high levels of aflatoxin. The seasonal variation of aflatoxin-albumin adduct and marked fluctuation of adduct with time in individual children need to be considered in the future planning of epidemiological studies using this marker of exposure.(ABSTRACT TRUNCATED AT 250 WORDS)