Intech Open Access
Aspergillus is a genus of fungus consisting of several hundred mould species found in various climates world-wide. Taxonomically, they belong to kingdom Fungi, phylum Ascomycota, class Eurotiomycetes, order Eurotiales, family Trichocomaceae and genus Aspergillus. There are several hundreds of Aspergillus species, including Aspergillus aculeatus, Aspergillus candidus, Aspergillus clavatus, Aspergillus niger, Aspergillus fumigates Aspergillus flavus, Aspergillus ustus, and Aspergillus tamari. 
Aspergillus species are highly aerobic and are found in almost all oxygen-rich environments, where they commonly grow as moulds on the surface of a substrate, as a result of the high oxygen tension. Commonly, fungi grow on carbon-rich substrates such as monosaccharides (e.g., glucose) and polysaccharides (e.g., amylose). Aspergillus species are common contaminants of starchy foods and grow in or on many plants and trees. In addition to their growth on carbon sources, many species ofAspergillus demonstrate oligotrophy, whereby they are capable of growing in nutrients-depleted environments or environments in which there is a complete lack of key nutrients. A. niger gives a prime example of this oligotrophic tendency, as it is found growing on damp walls as a major component of mildew. Species of Aspergillus are important medically and commercially. Some species are known to cause infection in humans and other animals .
Aspergillus flavus is a major food-borne pathogen that produces aflatoxin, a toxin that is carcinogenic . It is a leading cause of aflatoxicosis in poultry. Aflatoxicosis results from ingestion of aflatoxin in contaminated feed. Effects of the aflatoxicosis include toxicosis and immunosuppression . The toxins released during Aspergillus infection depress production parameters and, specifically, cause impaired growth in poultry, while the immunosuppressive effect predisposes the animals to many secondary infections from other pathogens, such as fungi, bacteria and viruses. The consumption of a mycotoxin-contaminated diet by broilers has been reported to induce haematological, biochemical and liver changes. Other documented effects include growth depression, economic losses, increased mortality, decrease blood cell count, lower egg production, lower feed consumption, reduced resistance to infectious disease and vaccination efficiency, gross and microscopic changes in the liver and other organs, such as hepatomegaly, paleness, and hydropic degeneration. Fatty changes in the adipocytes, bile duct, hyperplasia and periportal fibrosis are other effects of aflatoxicosis .