Fungal infections are not uncommon and most of the time it is limited to the skin, or cavities such as the mouth or vagina in women. It can cause significant discomfort and even cosmetic problems but fungal infections are usually not considered to be serious problem. However, some people are at risk of serious complications from fungal infections and this can even be deadly. Aspergillosis is one such case.
What is aspergillosis?
Aspergillosis is a fungal infection caused by the Aspergillus species of molds. In the human body, Aspergillus can cause a range of diseases but it is usually associated with the respiratory symptoms since the fungal spores enter the body through inhalation. However, in people with with weakened immune systems the spores can spread via the bloodstream to various parts of the body where it can cause disease.
Most of the time a healthy immune system provides sufficient defenses against aspergillosis. Most people are exposed to Aspergillus fungal spores but it does not cause an infection. However, approximately 1 out of 4 asthmatics in the United States test positive for Aspergillus antigen. Overall severe aspergillosis is rare and more likely to be seen in people who are immune compromised.
Types of Aspergillosis
Aspergillosis may present in several different ways depending on a host of factors, including immune sensitivity, strength of the immune system and other lung diseases.
- Allergic bronchopulmonary aspergillosis (ABPA) is where the Aspergillus fungi colonize the lower airways and cause a hypersensitivity reaction.
- Aspergilloma is a fungal ball that forms in a cavity within the lung tissue. These cavities are usually a result of pre-existing lung diseases such as tuberculosis or sarcoidosis.
- Chronic necrotizing pulmonary aspergillosis (CNPA) is less common and mainly seen in people who are immune compromised and with lung disease like COPD. It causes damage of the lung tissue.
- Invasive aspergillosis is often seen as the most severe type. It invades the blood vessels and can spread to the rest of the body. This type is more likely to occur with AIDS and organ transplantation.
Causes of Aspergillosis
There are many difference types of Aspergillus species of fungi. The more common types to cause disease in humans includes:
- Aspergillus fumigatus (A. fumigatus)
- Aspergillus flavus (A. flavus)
- Aspergillus niger (A. niger)
- Aspergillus terrus (A. terreus)
There are many other types of Aspergillus fungi but collectively these cause a minority of diseases in humans. From rotting leaves, compost, trees and plants to insulating material, air conditioning, heating systems, carperts, bedding and dust, Aspergillus is found in many places within the human habitat. However, only a small percentage of people who inhale the mold spores develop any disease.
Who is at risk?
Any person can be affected but in most healthy people the immune system provides adequate defenses to prevent infection and disease. The main risk factor is a weakened immune system. Pre-existing lung disease and any tissue damage due to a prior lung disease can also increase the risk of developing aspergillosis. Therefore the following conditions and factors may increase the likelihood of aspergillosis:
- AIDS, especially advanced stage.
- Bone marrow and organ transplantation.
- Chemotherapy (cancer treatment)
- Prolonged use of corticosteroids.
- Cystic fibrosis
- Tuberculosis (TB)
- Chronic obstructive pulmonary disease (COPD)
It is important to note that aspergillosis is not contagious. This means it cannot be passed from person to person. However, people living in the same environment are more likely to develop the condition if there are sufficient risk factors present in many individuals. One such case example is where both partners are HIV-positive with a low CD4 cell count.
Signs and Symptoms
The signs and symptoms depend on the part of the body that is affected. Since the lower airways and lungs are the most prone. Therefore most of the type aspergillosis presents with the following respiratory symptoms:
- Shortness of breath
- Bloody sputum (mainly in CNAP and aspergilloma)
- Loss of smell
- Runny nose or nasal congestion
Other non-respiratory symptoms that may occur especially with invasive aspergillosis includes:
- Unintentional weight loss
- Chest pain
- Bone pain
- Skin sores
- Visual disturbances
The signs and symptoms may be absent in the early stages of certain forms of aspergillosis. It may also be missed when other more common conditions are present.
Treatment of Aspergillosis
Aspergillosis can be treated with antifungal medication but this is not always curative in severe forms like when there is a delay in treating invasive aspergillosis. Other medication may also be necessary and in the case of an aspergilloma, surgery may be necessary. The choice of antifungal drug may vary among the different type of aspergillosis as follows:
- Amphotericin B for all forms of aspergillosis.
- Caspofungin for chronic necrotizing pulmonary aspergillosis and invasive aspergillosis.
- Itracanazole for allergic bronchopulmonary aspergillosis, aspergilloma and sometimes for chronic necrotizing pulmonary aspergillosis.
- Isavuconazole for invasive aspergillosis.
- Posaconazole for invasive aspergillosis.
- Voriconazole for chronic necrotizing pulmonary aspergillosis and invasive aspergillosis.
Prednisone, a corticosteroid, is mainly used to reduce inflammation in allergic bronchopulmonary aspergillosis. Corticosteroid use should be minimized among people who have been using steroids for prolonged periods and for people who are immune compromised. Long term use of corticosteroids, especially in high doses, can further weaken the immune system and increase the risk of aspergillosis.
The outlook for aspergillosis is good for allergic bronchopulmonary aspergillosis and aspergilloma. It is less so for chronic necrotizing pulmonary aspergillosis especially when treatment is delayed. The prognosis is poor for invasive aspergillosis especially with delayed treatment and in the backdrop of contributing conditions like HIV/AIDS. Resistance to certain classes of antifungal drugs also worsense the prognosis.
Aspergillosis is not contagious so reducing exposure to infected people is not necessary. Sometimes antifungal drugs may be used as a preventative measure for people with known risk factor. It is important to reduce exposure to the fungi by using protective wear such as face masks when working on a construction site or handling soil. These measures are mainly required by people with a weakened immune system and other risk factors.