Biology

1.1. OCCURRENCE AND DISTRIBUTION OF MYCOTOXIN

Approximately 25% of the world’s harvested crops are contaminated with mycotoxin every year, resulting in massive agricultural and industrial losses of billions of dollars as reviewed by the United Nations Food and Agriculture Organization and the World Health Oragnization (Marin et al., 2013; Pandya and Arade, 2016). Mycotoxins are avilable in various products such as animal feed, cereal crops, leguminous plants and animal products. Animal feeds commonly harbour mycotoxins are wheat bran, noug cake, pea hull and maize grain. Concentrated animal feedstuff harbours the growth of mycotoxin. Noug cake was justified the key source of aflatoxin contaminant among these concentrtaed animal feeds. Because, noug is indigenous and contributes up to 5% oil seed cap with its oil content varying from 30% to 50%. The oil production lines produce cooking oil by squeezing the nou seed and extricating the oil while the remaining noug cake is sold as animal feed to the feed processor or directly to the ranchers. Noug cake is progressively utilized in Ethiopia for its high nutrient content to increase animal productiivity and profitability in small scale. It is additionally exported to North America and Europe, where it is predominantly utilized for bird-feed (Gizachew et al., 2016). Mycotoxin contaminated intensity in leguminous crop varies geographically and groundnut is the main source of mycotoxin (Pereira et al., 2014; Marta and Bedaso, 2016). Groundnut seed is predominantly infected with Asperfillus flavus and Aspergillus niger (Gebreselassie et al., 2014). Cereal crops like barley like barley, sorghum, teff and wheat are the main source of mycotoxins. Mycotoxin can be transferred from feed to foodof animal origin, as this food is an essential route of human exposure. In addition to the toxicological effect in animals, they carry and tranfer products derived from animals such as meat, milk and eggs into the human food chain (Demissie, 2018). They can also be distributed in pre hravest period (time of plant growing), post harvest during processing, packaging, distribution and storage of food products. Conclusively, all crops and cereals that are stored improperly for a long time under favorable temperature and humidity facilitate mold growth and may be contaminated with mycotoxins (Ahmad and Jae-Hyuk, 2017); no boundaries will restrict fungal growth and mycotoxin production unless appropriate action is taken.

1.2. IMPORTANCE OF MYCOTOXIN

Mycotoxins have a wide range of negative and toxic effect in animals affecting their overall health and productively. Mycotoxin causes mycotoxicosis and causes major economic losses in animals due to lower productivity, increased incidence of disease and decreased reproductive performance (Enyiukwu et al., 2014). The ingestion of mycotoxins can produce both acute (short term) and chronic (medium and long term) toxicities ranging from death to chronic interferences with the function of the central nervous, cardiovascular, pulmonary system and of the alimentary tract. Some mycotoxins are carcinogenic, mutagenic, teratogenic and immunosuppressive (Adeyeye, 2016). Aflatoxin B for example, is one of the most potent hepatocarcinogens known (IARC, 2002). In the last 30 years, mycotoxins have drawn worldwide attention, firstly because of their potential effects on human health, secondly because of economic losses accruing from condenmed food or feed and decreased animal productivity and thirdly because of the significant impact of mycotoxin contamination on commodities traded internationally.

FACTORS AFFECTING THE PRODUCTION OF MYCOTOXIN AND CONTAMINATION OF FEED AND FOOD

A major difficulty in accessing the risk to human and animal health of mycotoxins is the multiplicity of factors that affect the production or presence of mycotoxin in food or feeds. The mere isolation and confirmation in food and feeds of mycotoxic fungal species does not indicate the presence of mycotoxins. Upon the advancement of the precise and sensitive techniques for qualitative and quantitative examination of mycotoxins, researchers found that different factors function interdependently to affect fungal colonization or mycotoxin growth classified the factors as physical, chemical and biological (D’Mello and MacDonald, 1997). Physical factors iclude environmental conditions viz temperature, relative humdity and insect infestation (Margherita et al., 2012). Physical factors such as time of exposure, temperature during exposure, humdity and degree of insect or other damage to product before exposure determine contamination of mycotoxins in the field or during storage. Chemical factors include the use of fertilizer and fungicide. Stresses such as drought, temperature increase and increase in relative humdity can selectively alter colonization and therefore alter the production of mycotoxin. Biological factors are based on the interaction between toxic fungal colonizing species and substrates. Although certain plant species are more vulnerable to colonization, environmental conditions may increase the vulnerability of other more resistant plant species (Margherita et al., 2012). Factors can be either intrinsic, extrinsic, processing each of which including moisture content, water activity, substrate type, plant type and nutrient composition; climate change, temperature, oxygen level; drying, blending, addition of perservatives, handling of grains; insect interaction, fungal strain and microbiological ecosystem respectively (Gabriel and Puleng, 2013).

Climate change has been proposed as perhaps the most imporatnt environmental issue facing the world and most affected has been Africa (Paterson and Lima, 2010). In fact, 2016 was identified as the hottest year in about a century, and consequently, a manifestation of this was Southern Africa’s 2016 El-nino drought episode, which resulted in agricultural losses amounting to million of US dollars ($). These imbalances, drastic changes in rainfall, temperature and patterns may increase the risk of pathogen migration and influence crop colonization by mycotoxigenic fungal genera (Magan et al., 2011). Since production of mycotoxin is climate dependent, changes in climate conditions have been suggested and proven to lead to possible drastic modification in fungal population and attendant mycotoxin production (Madgwick et al., 2011; Vander fel-Klerx et al., 2016).

A recent study predicts this fungal pathogens and pest proliferate from the equator to the Earth’s polar region at a rate of 5-6km annually (Magan and Medina, 2016). Drought and plant stress make crops more vulnerable to disease and fungal attack, thus increasing mycotoxin contamination, which reduces crop quality and yield, and decreases livestock production, disease tolerance and fertility. Futrthermore, the adaptation of known mycotoxic fungal species to climate change condition could lead to a more aggressive and invasive behaviour of the fungi resulting in the colonization of new territories, increased mycotoxin production and possibly the potential for the production of entirely new mycotoxin, which poses a significant threat to food security, safety and health in Africa and other developing countries (Magan and Medina, 2016; Medina et al., 2017). Type of substrate can also play a part in selecting for or against toxin producing strains of a given species, e.g. a high proportion of Aspergillus flavus toxin producing strains isolated from peanuts and cotton seed than from rice or sorghum. Food or feed contamination with mycotoxin can result from inadequate storage and/or handling of the harvested products.

Africa is the wrold’s poorest continent. Nearly one in five people living in Africa are undernourished and/or hungry, the highest incidence of such in the world. This can be of enormous importance for the quality of food commodities consumed in Africa (Hedden et al., 2016). There are insufficient resources to implement appropriate technologies and systems to control the proliferation of mycotoxin, and in dire need of food and ‘’quenching’’ hunger, the quality and safety of food ingested is totally irrevelant (although still clearly contaminated). Furthermore, limited public awareness of the danger posed by mycotoxin contamination of produce has been identified as a major factor responsible for its high incidence in Africa (Chihombori-Quao and Arikana, 2017). Majority of farmers produce and food handlers and/or processors are illiterate with virtually no knowledge of toxigenic mould growth implication.

CHAPTER THREE: ECONOMIC IMPACT ON MYCOTOXIN

The consumption of contaminated food globally accentuates a direct threat to food security, and the key elements contributing to contamination are micororganisms, specifically, fungi which produce mycotoxin. Approximately, 25% of the world’s food and feed supply is contaminated with mycotoxin, which has a negative effect on human and animal health, productivity, livlihood, household security, income and substantial economic loss (Enyiwkwu et al., 2014). The most significant effect of contamination with mycotoxins in Africa has been shown on human health (Marechera and Ndwiga, 2014). Although it is ectrremely difficult to estimate in Africa, the net monetarized effect of mycotoxin on human in Africa (including physical pain, death (in severe cases), temporary or permanent disability, loss of productivity, diagnostic costs, treatment, hospitalization and health care, pain, stress and reduced quality of life) may be enormous and demanding on national budget. In Senegal, a case in point, the cummulation health related costs of Aflatoxins (Afs) are estimated at no less than 12 million US$ of the nation’s GDP (ECOACAP, 2014). Also, mycotoxin affects the livestock industry. It makes anuimal prone to disease by weakening their response to immune system and vaccination against disease. In other ways, it can cause productivity loss in the dairy cow industry, particularly in the case of aflatoxins, additional losses involve the clearance time that farmers have to wait to allow animals to excrete all from their system (Marroquin et al., 2014).

Contamination can lead to direct econmic impact from importers through limited yeilds, price discounts, restricted end markets and export rejections. Microbial contamination has an adverse economic impact in reducing food and fiber crops yield, and food contamination with mycotoxin result in huge and universal economic crisis (USDA, 2006; Geremew, 2015).mycotoxin affect African agricultural trade name. Brand is am intangible feature that distinguishes an entity from its compeitiors, and comprises of expectations, imagination and loyalty to customers. In the field of accouting, brand is regarded as the most valuable asset on the balance sheet (Sharma, 2014; Soler Labajos and Jumenez-Zarco, 2016). The damage caused by mycotoxin to the brand can have a significant impact on business performance, productivity and business prospects. Unfortunately, mycotoxin has cause signioficant damage to Afircan food and agricultural trade brand, particularly in the export market. Some of the effect can be observed in the lack of trust for African feed or food resources, rejection and redundant scrutiny (which may lead to delay in transaction and perhaps more food spoilage). Between 2007 and 2012, thirteen consignments of groundnt and ground nut related products from Nigeria were rejecyted by (EU) European Union (Atanda et al., 2013). The National Agency for Food and Drug Administration (NAFDAC) of Nigeria reported that up to 42 semi – processed an processed food products of Nigeria origin destined for the European Union rejected in 2015 and 2016 for failing to meet the required standards (Ogunfuwa, 2018). Some of the items were destroyed, subjected to official detention, withdrawn from consumers from the market and re-dispatched. It should be noted that the cost of rejected food shipment is significant to about 10,000US$ per lot (Ogunfuwa, 2018).

3.1. HEALTH IMPLICATION OF MYCOTOXIN

Mycotoxin cause diseases in human and animals called mycotoxicosis and its severity depends on the rate of toxicity (Peraica et al., 1999). Mycotoxin is heat stable and endangers human health, animal production and economy of the country. Aflatoxins are acutely toxic, immunosuppressive, mutagenic, teratogenic and carcinogenic compounds (Blanchard and Manderville, 2016). Aflatoxin has carcinogenic, hepatogenic and mutagenic effects on human health when ingested, inhaled or absorbed through the skin, even at very low concentration (Zain, 2011; Wei et al., 2014). Aflatoxin causes aflatoxicosis that occurred in 1981, 2001, 2004 and 2005 in Kenya (Africa). is a potent mycotoxin and it is known to be hepatotoxic and hepatocarcinogenic (Geremew, 2015). The exposure of in conjuction with a low protein diet cause a decrease in the weight gain and kidney dyfunction in rats (Rotimi et al., 2018). Animal production is significantly reduced in countries with chronic aflatoxin contamination thus, minimizing the dietary protein and milk quality. In most African countries, poor knowledge about afaltoxin, adequate control measures to control contamination in field and storage, and the negative health effects of aflatoxin consumption are reported (Antonio et al., 2018). Additional factors on health impact are prevalent poverty and malnutrition (Kristine and Florian, 2018).

Fumonisin has been linked to esophagus cancer in human, although it affects animals in which it causes leukoencephalomalacia in equines and rabbits, pulmonary edema, hepatoxicity and nephrotoxicity. Ochratoxin causes neopropathy in humans; it is also the cause of Tunisian neopropathy and human (BEN) Balcan endemic neophropathy (Margherita et al., 2012). Ochratoxin A is carcinogenic and can cause upper urinary tract disease (Blanchard and Manderville, 2016). It is known for its teratogenic effects on the foetus in the womb, which possessess the ability to cross the placenta and cause malformation of the central nervous system and damage to the brain in rats (Malir et al., 2012). Deoxynivalenol causes nausea, vomiting, diarrhea, reproductive effects and toxicosis in human (Ali et al., 2013; Pinton and Oswald, 2014). Citrinin cause nephrotoxicity (Ali et al., 2018). It may affect kidneys and can cause severe renal failure (Degen et al., 2018). Patulin can be carcinogenic, immunotoxic and genotoxic on mammalian cells (Zain, 2011). Zearalenone can cause hormonal imbalance, reproductive effect and carcinogenicity when present in large quantities (Reddy et al., 2010; Blanchard and Manderville, 2016).

CHAPTER FOUR: DECONTAMINATION METHODS

Reducing mycotoxin contamination in agricultural commodities in many countries around the world is a very important problem which has led to various preventive measures (Ayofemi, 2019). All pre harvest strategies aim to prevent the development of toxigenic fungi and, hence, mycotoxins. However, once mycotoxins are produced, food contamination should be based on post harvest practices (Luo et al., 2018). The decontamination of mycotoxins from different agricultural product is a global issue, both scientific and practical. Mycotoxins have been shown to be eliminated by natural means such as thermal insulation, radiation treatment, and low plasma temperature, chemical methods such as oxidation, reduction, hydrolysis and absorption, and the biological methods with the use of biological agents (Lyagin and Efremenko, 2019). Physical and chemical decontamination has many limitation; they cause loss of nutrients, and are time consuming and ineffective, and require expensive equipment. In comparison, biological methods proved to be more effective, more specialized and more environmentally friendly (Wang et al., 2019).

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