Aflatoxins are toxic and carcinogenic mycotoxins found in a range of agricultural products, particularly cereals and nuts. Of especial concern are potentially high levels of these mycotoxins in maize and peanuts, which form part of staple diets in many parts of Asia.
The major fungus producing aflatoxins is Aspergillus flavus. However, another fungus,Aspergillus parasiticus and a few other minor species of Aspergillus can also produce these toxins.
Aflatoxins in crops:
All cereal crops can contain aflatoxins. Intensive cropping practices and decreased genetic diversity in cereal crops probably contribute to increased preharvest infections of commodities with fungi that produce aflatoxins. Preharvest contamination of crops with aflatoxins occurs in the temperate and tropical regions.
The seeds in growth-stressed plants are the most susceptible to fungal invasion and aflatoxin production. Postharvest contamination occurs worldwide when conditions in the storage unit exist for the growth of Aflatoxigenic fungi. Aflatoxigenic fungi can grow in feedlot manure.
Insects spread the spores of aflatoxigenic fungi to plants and the fungi colonize areas of insect damage. The flower and silk in corn can be portals of entry for species of Aspergillus.
Insect damage, timing of irrigation or rain, relative humidity around the bolls, stage of maturity and variety of cotton can be factors in causing preharvest contamination of cottonseed with aflatoxins.
The lipids and proteins in cottonseed enhance aflatoxin production. Peanut hay, peanuts and peanut by-products are an important source of mycotoxins. Aflatoxins generally are the most concentrated in the seeds.
The growth of aflatoxigenic fungi can occur in stored peanuts when moisture exceeds 8% and ambient temperature is above 25°C. Drought-stressed peanuts have decreased native resistance to infection by aflatoxin producing fungi.
Aflatoxins are not destroyed by the fermentation process. On a dry matter basis, the concentration of aflatoxins in the stillage, compared to aflatoxins in the feedstock, is increased due to the loss of starch.
Approximately 40% of the aflatoxins are in the syrup (distillers’ solubles) fraction and 60% are in the solids fraction.
Aflatoxins in animal feed stuffs:
Concentrated animal feedstuffs harbour highest level of mycotoxins. For instance, the lowest level of aflatoxin B1 contamination recorded from silage feed, which is roughages, was 7 μg/kg.
However, the highest level of aflatoxin B1 contamination traced about 419 μg/kg in concentrate animal feeds like wheat bran, noug cake and sweat pea hull. Noug cake was warranted as the main source of aflatoxin contaminant among those concentrated animal feeds.
Cereal crops like barley, sorghum, teff and wheat are the main source of mycotoxins. Aflatoxin and Ochratoxin detected from wheat, sorghum, teff and barley.
Among these cereal crops sorghum is the major source of mycotoxin contaminant because of wide spread storage of sorghum grain underground rise (pits) leading to elevated seed moisture contents.
Aflatoxin B1 was detected in 8.8% of the 352 samples analysed at concentrations ranging from trace to 26 μg/kg.
Aflatoxicosis in humans:
Mycotoxicoses in human like other toxicological syndromes can be categorized as acute or chronic. Acute toxicity has a rapid onset and an obvious toxic response, while chronic toxicity is characterized by low dose exposure over a long time period leading to cancer and other generally reversible effects.
Aflatoxin contributes factor for the disease like Kwashiorkor and Reye’s syndrome when children suffering it; immunosuppression in children.
Aflatoxicosis in animals:
Despite this, ruminants are less affected than non ruminant animals. However, production (milk, beef or wool), reproduction and growth can be altered when ruminants consume mycotoxin contaminated feed for extended periods of time.
Health effects occur in companion animals, livestock, poultry and humans because aflatoxins are potent hepatotoxins, immunosuppressant, and mutagens and carcinogens.
Control of mycotoxin problems:
Control of Aflatoxins is for the purpose of public health importance and economic improvement in the country. Hence, a number of strategies for reduction and control of aflatoxins have been considered in different areas of world.
The control of mycotoxins involves: 1, Prevention of mould or fungus growth in crops and other feedstuffs; 2, Decontamination of aflatoxin contaminated feeds/foods as a secondary strategy; 3, Continuous surveillance of mycotoxins in agricultural crops, animal feedstuffs and human food.
1. Prevention of mould or fungus growth in crops and other feedstuffs
It could be achieved by following strict hygienic precautions during harvesting, storage and processing of agricultural crops and feedstuffs.
Early harvesting of groundnuts resulted in lower Aflatoxin levels. Proper drying and storage of crops are effective tools for reduction of mould growth and mycotoxin production.
According to a trail in Guinea focused on through drying and proper storage of groundnuts, and it achieved a 60% reduction in mean Aflatoxin contamination.
2. Decontamination of mycotoxin contaminated feeds/foods
Includes physical, chemical and biological approaches. Physical approaches enlist as sorting, washing and crushing combined with de-hulling of maize grains, were effective in removal of Aflatoxin.
Chemical approaches are the activities incorporating application of fungicides such as prochloraz, propiconazole, epoxyconazole, tebuconazole, cyproconazole, Oltipraz, chlorophylin and azoxystrobin for reduction of Aflatoxin contamination.
Biological approaches depend on the development of atoxigenic fungi that compete with toxigenic fungi in the environment. Introduction of atoxigenic strains of A. flavus and A. parasiticus to soil of developing crops resulted in 74.3% to 99.9% reduction in the Aflatoxin contamination of peanuts in USA .
3. Continuous surveillance of mycotoxins in agricultural crops, animal feedstuffs and human food and awareness creation
It is a long term intervention strategy which has been advocated by World Health Organization . It is attractive for African countries to strengthen a nationwide surveillance, increase food and feed inspections to ensure food safety and local education and assistance to ensure that food grains and animal feeds are harvested correctly, dried completely and stored properly.
This could be achieved through awareness creation on the areas of what danger mycotoxins are posing to human and animal health and productivity. It could be performed through government bodies, private organizations, and national media networks in terms of newspapers and magazines as well as preparation of seminar and workshop that are used as avenue and bridge of information exchange and dissemina.
When mycotoxins are contaminated into foods, they cannot be destroyed by normal cooking processes. However, they can be prevented by recent advances in food processing, such as hazard analysis of critical control points (HACCP) and good manufacturing practices.
Moreover, several physical, chemical and biological methods can be applied to partially or completely eliminate these toxins from food and guarantee the food safety and health concerns of consumers.
Authors: Sana Majeed *1, Aisha Khatoon1, Zain- Ul- Abidin2, Ashiq Ali1, Muhammad Bilal1, Aneela Amin1,.
1 Department of Pathology, Faculty of Veterinary Science, University of Agricultur Faisalabad, Pakistan. 2 Veterinary Research Institute, Lahore, Pakistan.
* Corresponding Author Email: email@example.com