Aspergillus Fumigatus: Infection, Transmission & Diseases

Aspergillus fumigatus is the name given to a mold belonging to the genus Aspergillus. It is considered a high health risk for people with immunodeficiency.

What is Aspergillus fumigatus?

The mold Aspergillus fumigatus comes from the genus Aspergillus (watering can mold). The Latin name “fumigatus” is due to the smoky green coloration of the fungus. It is caused by a pigment within the spores. Aspergillus fumigatus is a human pathogenic fungus. This means that it can cause diseases in humans. Thus, mold toxins (mycotoxins) such as gliotoxin, fumagillin, fumitremorgins, verrucologens, and sphingofungins are synthesized by it.

Occurrence, distribution and properties

Worldwide, Aspergillus fumigatus is one of the most widespread life forms. It occurs in high or low abundance all over the world from Antarctica to the Sahara. For example, it can be found on rotting plants, in soil, on compost piles, on nuts and grains, and on moldy food, among other places. Sometimes Aspergillus spores (conidia) also spread through air conditioning systems with inadequate maintenance. Construction sites are also considered a conceivable source of mold infection, as larger quantities of fungal spores are present in construction dust. Growth of Aspergillus fumigatus occurs in highly flocculent or deeply folded colonies. The smooth short conidia carriers reach a height of about 300 micrometers. Occasionally, they may even be 500 micrometers. Their diameter ranges from 5 to 8 micrometers. Another typical feature is their greenish coloration up to the vesicle. On the stems, there is an opening into vesicles with a diameter of 20 to 30 micrometers. They have the same coloration as the conidia carriers. Their fertility is mostly only in the upper half. The conidia have the shape of a sphere and have an irregular surface. Their diameter varies between 2.5 and 3 micrometers. The first stage of life of Aspergillus fumigatus takes place as conidia. The extremely small mold spores are highly resistant to desiccation, high temperatures and even disinfectants. If the spores have sufficient nutrients and water, they can germinate, resulting in the formation of individual hyphae. These hyphae branch out increasingly as they progress. This results in the formation of a so-called mycelium (hyphal network). At the mycelium surface individual conidia carriers develop. The function of these heads is the production of further spores. Each conidia carrier produces about 10,000 new fungal spores. The spores are spread by the wind. Their multiplication process takes place asexually. Aspergillus fumigatus is a saprophytic fungus. This means that it feeds on dead plant parts. With the help of its versatile metabolism, it is able to decompose many substances. In addition, it can withstand temperatures of up to 48 degrees Celsius. Aspergillus fumigatus spores enter humans through inhaled air. They are so small that they can penetrate into the human alveoli (pulmonary alveoli). Skin or mucosal lesions are another means of transmission. The preferred contact sites include compost, organic waste garbage cans, potting soil and wallpaper. However, moisture accumulation in the home or basement can also promote the spread of Aspergillus fumigatus.

Diseases and complaints

Serious health problems are possible due to Aspergillus fumigatus. In the case of a mold infection of humans, doctors speak of aspergillosis. In most cases, this shows up in the lungs or the sinuses. However, areas such as the gastrointestinal region, the nervous system or the skin are also sometimes affected. While mold is usually not a threat to people with an intact immune system, those with a weakened immune system due to pre-existing conditions or taking immunosuppressants are considered particularly at risk. In healthy people, the mold spores are successfully fought off by the immune system, but in sick people they can become lodged in the lungs, sinuses or auditory canal and trigger a fungal infection there. In Germany alone, there are about 5000 infections with Aspergillus fumigatus every year. About 90 percent of all aspergilloses are caused by this type of mold.The infection is fatal in one out of two patients. A major problem is that there are hardly any effective drugs available to combat aspergillosis. Research into an effective drug is still ongoing. The progress of research is hampered by the fact that the structure and metabolism of human cells and fungal cells are similar. Because of the dramatic course of the disease, doctors administer antifungal drugs with a broad spectrum of action even when aspergillosis is merely suspected. There are different types of fungal infections caused by Aspergillus fumigatus. They depend on which organ is affected by the infestation. For example, there is aspergilloma in the paranasal sinuses. It shows up in the context of sinusitis, so that patients often do not even notice the fungal infestation. In the worst case, the fungal spores spread to the brain. Aspergilloma in the lungs often affects people who suffer from lung diseases such as bacterial pneumonia, tuberculosis or bronchial carcinoma. In this case, the fungal spores settle in cavities of the lungs caused by these diseases. In addition, severe allergic reactions are possible, manifested by coughing and sputum.