Aspergillus is a common genus of mold found globally. It is characterized by spore-forming structures resembling a holy water sprinkler. Its microscopic spores are regularly dispersed into the air, making human exposure common.
Diverse Forms and Habitats
Aspergillus produces microscopic spores called conidia, easily carried by air currents. These fungi are saprophytic, obtaining nutrients by absorbing dissolved organic material from decaying matter. Aspergillus species are aerobic and thrive in oxygen-rich environments, growing on various carbon-rich substrates like sugars and starches.
These molds are commonly found in soil, water, and decaying vegetation, including compost and haystacks. Indoors, Aspergillus can be found in household dust, on damp bathroom walls, or on building materials. Of over 185 identified species, about 20 cause opportunistic infections in humans, with Aspergillus fumigatus, Aspergillus flavus, and Aspergillus niger being frequently encountered.
Health Effects of Aspergillus
Aspergillus can affect human health through infections (aspergillosis) or exposure to mycotoxins. Most healthy individuals breathe in Aspergillus spores without illness, as their immune systems prevent infection.
Aspergillosis (Infections)
Aspergillosis encompasses a spectrum of diseases, from allergic reactions to severe invasive conditions, usually affecting the respiratory system. Allergic bronchopulmonary aspergillosis (ABPA) occurs when the fungus triggers an allergic reaction, often in individuals with pre-existing conditions like asthma or cystic fibrosis. Symptoms include fever, coughing that may produce blood or mucus plugs, and worsening asthma.
Chronic pulmonary aspergillosis (CPA) often develops in people with existing lung cavities from conditions such as tuberculosis or emphysema. This can lead to an aspergilloma, or “fungus ball,” a tangled mass of fungal fibers and cells that forms within lung cavities. Symptoms may include a persistent cough, sometimes with blood, wheezing, and shortness of breath.
Invasive aspergillosis (IA) is the most severe form, where the infection rapidly spreads from the lungs to other organs like the brain, heart, kidneys, or skin. This form primarily affects individuals with significantly weakened immune systems, such as those undergoing cancer chemotherapy or organ transplantation. Symptoms can include fever, chills, coughing up blood, shortness of breath, chest pain, and headaches. If left untreated, it can be fatal.
Mycotoxins
Certain Aspergillus species, such as Aspergillus flavus and Aspergillus parasiticus, produce toxic compounds called mycotoxins. Aflatoxins are frequently found contaminating crops like corn, peanuts, cottonseed, and tree nuts. Exposure to large doses of aflatoxins can cause acute poisoning, leading to liver damage and potentially being life-threatening.
Aflatoxins are also genotoxic, meaning they can damage DNA, and are classified as Group 1 carcinogens by the International Agency for Research on Cancer (IARC), particularly linked to liver cancer. Another mycotoxin, ochratoxin A, produced by species like Aspergillus ochraceus, commonly contaminates cereals, coffee, dried fruits, and wine. Ochratoxin A can cause kidney damage and may affect fetal development and the immune system.
Identifying and Treating Aspergillus-Related Conditions
Diagnosing Aspergillus-related conditions can be challenging due to the fungus’s common presence and symptoms often resembling other lung conditions. Diagnosis typically combines medical history, symptom review, and specific tests. Imaging studies are commonly used to visualize the lungs and identify fungal masses or infiltrates.
Chest X-rays or computed tomography (CT) scans can reveal fungal masses, such as an aspergilloma, or signs of invasive aspergillosis and ABPA. A sputum test, examining respiratory secretions, helps confirm Aspergillus presence. Blood tests detect antibodies or antigens, while a skin prick test indicates an allergic response.
Treatment approaches are tailored to the specific type of aspergillosis and the patient’s overall health. Antifungal medications are standard for invasive aspergillosis, with voriconazole often first-line and amphotericin B an alternative. For ABPA, oral corticosteroids are commonly prescribed to reduce inflammation, sometimes combined with antifungal agents like itraconazole. Asymptomatic aspergillomas may only require observation. If they cause symptoms like bleeding, surgical removal may be preferred, as antifungals may not penetrate the fungal mass.
Minimizing Exposure and Risk
Reducing exposure to Aspergillus spores is practical, especially for those with compromised immune systems or pre-existing respiratory conditions. Controlling indoor moisture is a primary strategy. Keep humidity below 60% with dehumidifiers and ensure proper ventilation in bathrooms and kitchens to deter mold growth. Promptly repairing leaks and water damage also prevents ideal conditions for Aspergillus.
Personal protective equipment can offer protection in high-risk environments. For weakened immune systems, avoid dusty areas like construction or excavation sites, or wear an N95 respirator mask if avoidance is not possible, to reduce spore inhalation. When gardening or handling decaying organic matter, wearing shoes, long pants, and long-sleeved shirts is advisable to minimize skin exposure. Good food safety practices also prevent mycotoxin exposure. This includes proper storage of grains and nuts, and discarding any moldy food.