Oct 07, 2009    Views: 13170


In agriculture, Aspergillus originally was considered a serious problem largely because of its prevalence in the biodeterioration of stored crops and as an opportunistic pathogen of field crops, particularly under high moisture conditions. During the early 1960s, the discovery of aflatoxins associated with massive deaths of poultry, trout and other domesticated animals species worldwide raised new awareness that these fungi posed threats to foods and feeds beyond their ability to rot plant materials. Research on aflatoxins led to many new fungal toxins being discovered from species of Aspergillus and other common moulds. In addition to aflatoxins, other important Aspergillus mycotoxins include ochratoxin, patulin and fumigillin.
See also: Microbial Toxins and Microbial Biodegradation

Aflatoxins are still recognized as the most important mycotoxins. They are synthesized by only a few Aspergillus species of which A. flavus and A. parasiticus are the most problematic. The expression of aflatoxin-related diseases is influenced by factors such as age, nutrition, gender, species and the possibility of concurrent exposure to other toxins. The main target organ in mammals is the liver so aflatoxicosis is primarily a hepatic disease. Conditions increasing the likelihood of aflatoxicosis in humans include limited availability of food, environmental conditions that favour mould growth on foodstuffs, and lack of regulatory systems for aflatoxin monitoring and control.
See also: Foodborne Pathogens: Microbiology and Molecular Biology

A. flavus
and A. parasiticus are weedy moulds that grow on a large number of substrates, particularly under high moisture conditions. Aflatoxins have been isolated from all major cereal crops, and from sources as diverse as peanut butter and marijuana. The staple commodities regularly contaminated with aflatoxins include cassava, chillies, corn, cotton seed, millet, peanuts, rice, sorghum, sunflower seeds, tree nuts, wheat, and a variety of spices intended for human or animal food use. When processed, aflatoxins get into the general food supply where they have been found in both pet and human foods as well as in feeds for agricultural animals. Aflatoxin transformation products are sometimes found in eggs, milk products and meat when animals are fed contaminated grains.
See also: Foodborne Pathogens: Microbiology and Molecular Biology

Human exposure to aflatoxins exposure is difficult to avoid because A. flavus grows aggressively in many foods at all stages of the food chain: in the field, in storage and in the home. Evidence for acute human aflatoxicosis has been reported from several underdeveloped countries such as India and Thailand. The symptoms of severe aflatoxicosis include oedema, hemorrhagic necrosis of the liver and profound lethargy. Further, aflatoxins are potent carcinogens, especially aflatoxin B1. Based on epidemiological studies done in Asian and Africa, in 1988 the International Agency for Research on Cancer, part of the World Health Organization, placed aflatoxin B1 on the list of human carcinogens. In developed countries, the emphasis on keeping aflatoxin out of the food chain concerns its carcinogenic potential. Strong regulatory limits (4-30 ppb) have been established for many commodities.
See also: Microbial Toxins: Current Research and Future Trends

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