Incidence of aflatoxins, fumonisins, trichothecenes and ochratoxins in Nigerian foods and possible intervention strategies (original) (raw)

Mycotoxins are toxic secondary metabolites produced by some species of fungi. Aflatoxins, fumonisins, trichothecenes and ochratoxins are the common mycotoxins in Nigeria. Aflatoxin is the most frequently reported in literatures, with trichothecenes being the least, they cause yield loss to farmers as well as constituting major health risk to humans. The occurrence of mycotoxins in food is a serious problem that Nigeria is facing presently, as it continues to pose threat to feed and food safety of animals and humans. There is the need to seek for approaches that would lead to reduction in their toxicity. The practice of good sanitary measures right from the farm to storage, creation of awareness campaign to indicate the toxic effects associated with mycotoxin poisonings in humans and livestock, and proper evaluation of food crops for its presence can go a long way in achieving the target reduction in incidence of mycotoxins in Nigeria. 1.0 Introduction Mycotoxins are secondary metabolites of fungal origin which produce toxic responses when ingested by animals or humans. The word 'mycotoxin' is a combination of a Greek word, 'mykes' meaning 'fungus' and a Latin word 'toxicum' meaning 'by poison' (Rai et al., 2012). Mycotoxicosis is a term used to denote the diseases that result from the ingestion of mycotoxin by animals and humans (Nierman et al., 2008). The acuteness of a specific mycotoxicosis may vary in different victims. Various factors determine the severity of a mycotoxin; among them are the level of toxicity, dosage, age, nutritional and immunity status of the victim (Peraica et al., 1999). The general attraction to the study of mycotoxins started in 1960 when more than 100,000 turkeys died in London, England after consuming contaminated groundnut meal that was imported from Brazil (Blount, 1961). The disease that resulted was called 'Turkey X' disease. Aspergillus flavus was later isolated from the groundnut meal and the toxic agents named 'aflatoxin' (A. flavus toxin) accordingly (Splensley, 1963; Kensler et al., 2011). The word 'mycotoxin' was then coined in 1962 after the Turkey X incident. Most mycotoxins of concern are produced by three genera of fungi, namely, Aspergillus, Penicillium, and Fusarium. These are the predominant fungal genera associated with food grains during storage (CAST, 2003). These genera are considered significant because of their ubiquity in the environment and their ability to produce various types of mycotoxins like aflatoxins, fumonisins and ochratoxins (Juan et al., 2010). However, the presence of these fungi does not necessarily imply the presence of toxins. The mycotoxigenic fungi can be classified as either field or storage fungi. It should be noted that a fungus may produce several mycotoxins and a mycotoxin may be produced by different fungi (Fernandez-Cruz et al., 2010). There are intrinsic and extrinsic factors which influence the production of mycotoxins. The intrinsic factors include pH, water activity (a w) and redox potential of the substrate while the extrinsic factors are the relative humidity, temperature and oxygen availability of the environment where the commodities are produced, stored or processed (Whitlow and Hagler, 2004; Nagwa et al., 2013). Over 400 types of mycotoxins have been reported (Bhat et al., 2010), but only four (aflatoxins, fumonisins, trichothecenes and ochratoxins) will be discussed in this review. While the other mycotoxins are important for studies, aflatoxins, fumonisins, trichothecenes and ochratoxins are of greater interests because of their prevalence in agricultural produce and the harmful effects they exert when they are consumed by animals and humans (Richard, 2007). The Food and Agriculture Organization (FAO) estimated that about 25% of the world's agricultural produce is contaminated with mycotoxins which cause huge losses for farmers (Wu, 2007). These losses are measured in reduced crop yields, lower quality, reduced animal performance and reproductive capabilities, and increased disease incidence. The biochemical properties of mycotoxins are diverse, and their toxic effects are exceedingly variable.