What is Aspergillus?

The aspergillus species includes more than 150 types of mold that occur widely in the indoor and outdoor environment. Although most of the molds are harmless, a few can cause serious illnesses in people with a weakened immune system, underlying lung disease or asthma. These illnesses, collectively called aspergillosis, range from allergic responses to severe and sometimes fatal infections.

Aspergillus is a fungus (or mold) that is very common in the environment. It is found in soil, on plants and in decaying plant matter. It is also found in household dust, building materials, and even in spices and some food items. There are lots of different types of Aspergillus, but the most common ones are Aspergillus fumigatus and Aspergillus flavus. Some others are Aspergillus terreus, Aspergillus nidulans, and Aspergillus niger.

A fungus ball in the lungs may cause no symptoms and may be discovered only with a chest x-ray. Or it may cause repeated coughing up of blood and occasionally severe, even fatal, bleeding. A rapidly invasive Aspergillus infection in the lungs often causes cough, fever, chest pain, and difficulty breathing.

Aspergillus usually affects open spaces in the body, such as cavities that have formed in the lungs from preexisting lung diseases. The infection may also occur in the ear canals and sinuses. In the sinuses and lungs, aspergillosis shows up as a ball (aspergilloma) composed of a tangled mass of fungus fibers, blood clots, and white blood cells. The fungus ball gradually enlarges, destroying lung tissue in the process, but usually does not spread to other areas.

Aspergillus may cause a broad spectrum of disease in the human host, ranging from hypersensitivity reactions to direct angioinvasion. Aspergillus primarily affects the lungs, causing 4 main syndromes, including allergic bronchopulmonary aspergillosis (ABPA), chronic necrotizing Aspergillus pneumonia (or chronic necrotizing pulmonary aspergillosis [CNPA]), aspergilloma, and invasive aspergillosis. However, in patients who are severely immunocompromised, Aspergillus may hematogenously disseminate beyond the lung, potentially causing endophthalmitis, endocarditis, and abscesses in the myocardium, kidney, liver, spleen, soft tissue, and bone.

Tentative diagnosis can be made with clinical signs as well as the absence of bacterial infection in moist exudates. A blood test showing an elevation in white blood cell count, mild anemia and an elevation in the monocytes also supports this diagnosis. X-rays should be taken on any suspect patient-many times the radiograph will reveal densities or nodules consistent with aspergellomas. Additionally, your avian veterinarian should take samples and attempt to culture the fungus in specially prepared culture media. Blood should also be submitted for serologic evaluation.

Aspergillus fumigatus is widely present in nature and produces tremendous numbers of spores in a few days when placed in warm and moist conditions. Favored environments for the mold are damp litter in stubble fields, on moldy grass along riverbanks, on moldy grain or meal, and on rotting plant and animal material, especially damp hay and straw.

Everyday exposure to aspergillus is rarely a problem for people with healthy immune systems. When mold spores are inhaled, immune system cells simply surround and destroy them. But people who have a weakened immune system from illness or medications have fewer infection-fighting cells. This allows aspergillus to take hold, invading the lungs, and in the most serious cases, other parts of the body.