The effect of mycotoxin exposure on the growth of infants and young children in deep rural areas of the Eastern Cape Province, South Africa

Abstract

Malnutrition (especially undernutrition) is a global public health concern in developing countries such as South Africa (SA) and is predominately prevalent among infants and young children (IYC) less than 24 months of age. In rural, low-income communities of SA, the stunting prevalence is particularly high. These areas are usually subsistence farming communities that are mostly relying on maize as a staple food. Recent research indicated that environmental factors such as mycotoxin exposure are a possible contributing factor to impaired growth among children. Mycotoxins are toxic secondary metabolites produced by naturally occurring food-borne fungi. The mycotoxins present in the Eastern Cape (EC) are fumonisins (FB), deoxynivalenol (DON) and zearalenone (ZEA), aflatoxins (AF) are known to be absent. However, very little is known about the association between mycotoxin exposure and child growth and the complexity of confounding factors. The interaction between mycotoxin exposure and impaired growth could be of crucial importance in the reduction of morbidity and mortality amongst young children in rural areas of SA. Various factors influence growth causing undernutrition. These factors include amongst others, repeated infectious diseases, poor nutrient intake and poor sanitary infrastructure. The overall aim of this thesis was to firstly determine multi-mycotoxin exposure levels of infants and young children and its effects on infant growth parameters in deep rural areas of the EC, and secondly to determine the effect (if any) that these mycotoxins have on the growth of these IYC. To achieve the aim of this study, the following specific objectives were identified: i) to describe the basic sociodemographic situation of households as well as general health and maize dietary intake of infants and young children; ii) to determine multi-mycotoxin exposure of children (0 - 24 months) in rural maize-subsistence farming areas of EC, South Africa; iii) to assess child growth indicators during the first 24 months of life and iv) to compare multi-mycotoxin exposure and infant and child growth at 0 - 12 months and 13 - 24 months. The current study is a sub-study of the larger Philasana study. The primary aim of the PhilaSana study was to investigate the various factors influencing infant feeding and growth. This was in the form of a longitudinal, observational study and followed pregnant women and their infants up to the age of two years. The study was conducted in the Amatole District Municipality in the EC. A total of 234 infants and young children were included in the study, although not all of them were followed up, due to availability on time of visit. Snowball sampling was used to identify possible participants. The first article in this sub-study measures mycotoxin concentration levels and was thus a cross-sectional study design. The last two articles written in this sub-study used data collected at some of the PhilaSana time points and utilised as a longitudinal study design. Maize consumption of the IYC was determined with a quantitative food frequency questionnaire (the RAPP tool), which was designed and validated specifically for this Xhosa population. Once mean daily maize intake (cooked) was determined it was converted to raw maize intake based on recipes and ratios (raw: cooked) established during the development of the questionnaire. Once the raw maize intake of the IYC were obtained, the level of mycotoxin contamination in the raw maize was analysed. Thereafter, mycotoxin exposure was calculated and expressed as a probable daily intake (PDI, μgkg-1 body weight day-1). Growth of IYC was measured as weight and length / height. Current weight and length / height, head circumference (HC) and mid upper circumference (MUAC) z-scores were determined as well as birth anthropometric information as provided in the Road to Health Booklet (RTHb). Change in growth was determined by subtracting current z-score from the previous z-score or birth z-scores. This was conducted to determine the direction of growth (in other words is the infant growing at the required rate or not). WHO Anthro plus was used to determine z-scores. Furthermore, confounding factors such as health status (HIV and TB) of the children, food intake and socio-demographic factors were examined. The mean total FB, DON and ZEA levels for analysed home-grown maize samples were 1035, 24.5 and 31.0 μg kg-1 respectively. Furthermore, mean daily maize intakes of children 0 - 24 months ranged from 1.6 g - 321 g day-1. The mean probable daily intakes (PDI) of these children for total FB was above the PMDTI, while that of DON and ZEA were below the PMDTI. Approximately 16% of the infants 0 – 12 months of age were stunted, however none of them were wasted or underweight. Furthermore, it was determined that infants were exposed to mean FB, DON and ZEA above the Provisional Maximum Tolerable Daily Intake (PMDTI). The mean length of infants exposed to high FB exposure levels was 4.4 cm shorter than the low exposed group, though they had a mean weight difference of only 0.3 g. ANCOVA results indicated that high FB exposure was significantly associated with LAZ, WAZ scores and reduction in length of infants 0 - 12 months. Furthermore, 34% of the young children were stunted within the 13 - 24 age group, while none of the children were wasted and underweight. ANCOVA also showed a significant difference in WLZ and LAZ changes with high FB exposure (p < 0.05). Linear regression further indicated that FB, DON, and ZEA exposure was associated with reduction in weight gain (g kg-1 day-1). The EC residents are predominately maize subsistent farmers. Maize samples analysed from the maize cobs collected in EC, had high levels of mycotoxins. Infants and young children from this area consume home-grown maize-based dishes such as soft porridge, maheu (fermented maize-meal) and maize meal. However, the home-grown maize in this area is contaminated with three mycotoxins, FB, DON and ZEA. The exposure levels of infants in this area was observed to be above the PMDTI, therefore posing serious health threats. Results concluded that FB exposure might be amongst the contributing factors of growth impairment in this area. The conclusion is in support of the notion that mycotoxin exposure results in impaired growth, due to poor appetite, reduced intestinal permeability and inflammatory reactions. The results are also in support of previous knowledge that z-scores and length of children are associated with high mycotoxin exposure. Furthermore, the results add on to explain further that growth changes are associated with mycotoxin exposure; therefore, growth rate is an issue not to be ignored regarding mycotoxin exposure. On the other hand, children were discovered to not be gaining sufficient weight in relation to their length, though they were gainingweight in relation to their current age. This alarming finding further explained growth impairment of the participants, the weight again was expected to be due to maize intake. Dietary diversification and safe complementary feeding are essential to curb growth impairment (especially in terms of length) and mycotoxin exposure amongst infants and children 0 - 24 months of age in EC