Aspergillus Species: Health Risks and Common Types

Aspergillus is a widespread mold whose spores are in the air we breathe daily. For most people, this exposure is harmless, as the body’s response is determined by an individual’s immune system. While the majority of strains are not harmful, a few can cause a range of diseases that primarily affect the respiratory system.

Common Habitats of Aspergillus

Aspergillus is a highly adaptable fungus that acts as a decomposer in the ecosystem. Outdoors, it is abundantly found in soil and on decaying organic matter, such as fallen leaves and compost piles.

The mold is not restricted to the outdoors; it readily colonizes indoor spaces as well. Aspergillus spores can be a common component of household dust. They flourish in areas where moisture is present, such as damp basements, bathrooms, and around leaky pipes. Water-damaged building materials, including drywall and wood, provide an ideal substrate for its growth.

Heating, ventilation, and air conditioning (HVAC) systems can become reservoirs for Aspergillus. The dark, often damp conditions within these systems can support mold growth, allowing spores to be circulated throughout a building.

Health Implications of Aspergillus Exposure

The clinical presentation of Aspergillus-related disease exists on a spectrum, from allergic reactions to life-threatening invasive infections. These conditions are not contagious and cannot be spread from person to person.

Allergic Bronchopulmonary Aspergillosis (ABPA) is an allergic reaction to Aspergillus spores that primarily affects individuals with pre-existing respiratory conditions. It is most commonly seen in people with asthma or cystic fibrosis. In these individuals, the immune system overreacts to the inhaled spores, leading to inflammation of the airways that can exacerbate their underlying lung disease.

In some cases, Aspergillus can form a fungus ball, known as an aspergilloma, within the lungs. This occurs when the mold grows in pre-existing cavities in the lung tissue, which may have been caused by previous illnesses like tuberculosis or sarcoidosis. The aspergilloma is a mass of fungus fibers, blood clots, and white blood cells that can cause a chronic cough.

Chronic pulmonary aspergillosis is a long-term infection that can develop in individuals with underlying lung disease. Unlike an aspergilloma, this condition involves the active invasion and destruction of lung tissue. It can lead to the formation of new cavities and a gradual decline in lung function.

The most severe form of disease is invasive aspergillosis. This occurs when the infection spreads from the lungs through the bloodstream to other organs, such as the brain, heart, skin, or kidneys. This type of infection progresses rapidly and can be fatal.

Identifying At-Risk Individuals

The primary factor determining risk for aspergillosis is the status of an individual’s immune system. People with compromised immunity are more vulnerable to all forms of the disease, particularly the invasive type.

This high-risk group includes individuals undergoing chemotherapy for cancer. People who have received an organ or bone marrow transplant are also at increased risk because they take immunosuppressive drugs to prevent rejection. Patients in the later stages of AIDS may also have a heightened risk.

Individuals with pre-existing lung conditions are another at-risk group. People with asthma and cystic fibrosis are more prone to developing allergic reactions to the mold. Those with chronic lung diseases such as chronic obstructive pulmonary disease (COPD), emphysema, or a history of tuberculosis that has left cavities in the lungs are more susceptible to developing aspergillomas and chronic pulmonary aspergillosis.

Long-term use of corticosteroid medications can also increase the risk of developing aspergillosis. These drugs, while effective at reducing inflammation for a variety of conditions, can also suppress the immune system’s ability to respond to fungal invaders.

Medical Diagnosis and Treatment

Diagnosing an Aspergillus-related illness involves a combination of imaging, laboratory tests, and clinical evaluation. Healthcare providers use imaging techniques like chest X-rays or computed tomography (CT) scans to look for signs of infection in the lungs, such as nodules or cavities.

To confirm the diagnosis, a sample of tissue or fluid is often required. A provider might perform a biopsy, collecting a small piece of tissue from the lungs or sinuses for examination in a laboratory. Samples of respiratory fluids, such as sputum, can also be cultured to see if Aspergillus mold will grow. Blood tests are another diagnostic tool that can detect Aspergillus antigens or antibodies the body produces in response to the infection.

Treatment for aspergillosis depends on the specific type of disease. Antifungal medications are the primary treatment for most forms of aspergillosis, particularly invasive and chronic types. The choice of antifungal medication and the duration of treatment will vary based on the severity of the infection and the patient’s overall health.

In some situations, surgery may be necessary. For example, an aspergilloma that is causing significant bleeding in the lungs may need to be surgically removed. For allergic forms of the disease, such as ABPA, treatment may involve corticosteroids to manage the immune system’s inflammatory response, in addition to antifungal therapy.