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HomeLearn MoreCommon MoldsAspergillus

Aspergillus

The fungus Aspergillus has close to 200 species and varieties. This mold is widely distributed from the arctic region to the tropics. Aspergillus species are frequently found in air and soil.

How do species of Aspergillus affect our lives?

Species of Aspergillus affect our lives in several ways:

• Biodeterioration
  
  Species of Aspergillus are capable of utilizing an enormous variety of organic material for food because of their ability to produce a large number of enzymes. Under humid conditions, Aspergillus species grow on leather and cloth fabrics, reducing their value and imparting musty odour to shoes and clothing. Several species are frequently found on grains and exposed foodstuffs where they cause decay and subsequent loss of food.
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• Medical Effects
  
  As concerns health, the most important species of Aspergillus are Aspergillus clavatus, A. flavus, A. fumigatus, and species from the group of A. niger, and A. versicolor. These molds have been classified by some authorities as being toxigenic or pathogenic and instant action is required when they appear in occupied indoor environment.

• Mycotoxins
  
  Aspergillus species produce toxic compounds, the most well known being aflatoxins. Aflatoxin is a class 1 carcinogen produced by strains of Aspergillus flavus and Aspergillus parasiticus. The best known toxic metabolites of A. fumigatus are mainly fumigaclavines A, B, C, and D, spinulosin and tremorgenous toxins, e.g. verruculogen. A. niger strains produce toxic metabolites belonging to malformins A1, A2, B1, B2, C and oxalic acid. On building material, strains of A. versicolor produce the toxic class 2A carcinogenic sterigmatocystin.
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• Opportunistic Pathogens
  
  Aspergillus fumigatus is an animal and human pathogen causing a group of diseases commonly referred to as Aspergilloses. Aspergillosis of the lungs is believed to be the most serious of these diseases and is quite common in birds and various mammals including humans. Other species of Aspergillus associated with Aspergilloses are Aspergillus flavus, Aspergillus niger and Aspergillus terreus. Aspergillus niger has been reported as causing ear, nose and lung infection particularly in immuno-compromised individuals.
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• Allergic Reactions
  
  Many species of Aspergillus produce dry, hydrophobic spores that are easily inhaled. Due to their small size, about 70 % of spores of A. fumigatus are able to penetrate into the trachea and primary bronchi and close to 1 % into alveoli. Inhalation of spores of Aspergillus is a health risk. Aspergillus clavatus is allergenic causing the occupational hypersentivity pneumonitis known as malt worker's lung.
  

Occurrence of Aspergillus species in indoor environments

Alternaria alternata is recognized as an important allergen with airborne spores and mycelial fragments being responsible for the allergic symptoms in individuals with rhinitis or bronchial asthma. Alternaria sensitivity can also lead to severe and potentially fatal asthma. Studies have shown that up to 70 % of mold-allergic patients have skin test reactivity to Alternaria. It has also been shown that prolonged heavy exposure to Alternaria alternata spores and mycelial fragments mimics that of other allergens such as cat dander and dust mites. It has also been recorded as an opportunistic pathogen causing skin diseases particularly in immunocompromised patients such as the bone marrow transplant patients.

It is generally believed that the amount of airborne spores of Aspergillus spp. in indoor air is higher than outdoors at any given time. In the home, the amount of spores in the air is significantly increased when cleaning is carried out mechanically, for example, when carpets are vacuum cleaned. Some studies on prevalence of Aspergillus species in indoor environment documented A. fumigatus in kitchens and bathrooms, A. versicolor and A. repens in mattresses and carpets, A. versicolor and A. fumigatus in basements, A. fumigatus, A. niger and A. flavus in flower pot soil, A. versicolor and A. fumigatus in various pad materials.

Species of Aspergillus have been isolated from damp walls, wallpaper, PVC/paper wall covering, gypsum board, floor, carpet and mattress dust, upholstered-furniture dust , acrylic paint, UFFI, leather, HVAC insulations, filters and fans, humidifier water, shoes, leather, bird droppings and potted plant soil, plastic and decomposing wood.



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