Aspergillus

Aspergillus is a common type of fungus that grows on decaying vegetation, such as compost heaps and fallen leaves. It can also be found in air-conditioning systems and hospitals.

Some people with asthma are allergic to the fungal spores. These can trigger an asthma attack if inhaled. Some people will develop a condition known as allergic bronchopulmonary aspergillosis (ABPA), in which asthma worsens significantly as a result of increased lung inflammation.

In rare cases, a person may suffer serious lung or other organ infection with this fungus. Some severely ill people, or those whose resistance is lowered because they are taking medications which suppress their immune system, may be affected.

The structure of the lungs

The lungs are inside the chest, protected by the ribcage and wrapped in a membrane called the pleura. The windpipe (trachea) splits into two tubes, called bronchi, that service one lung each. The bronchi divide into smaller tubes called bronchioles, which ultimately branch into even smaller air sacs called alveoli. Each alveolus has a fine mesh of capillaries. This is where the exchange of oxygen and carbon dioxide takes place.

A person with asthma who is allergic to Aspergillus will have spasms of the bronchioles, which causes breathlessness and wheezing.

Allergens and asthma

Nine out of 10 people with asthma find their symptoms worsen when they are exposed to certain triggers or allergens. An allergen is any substance that causes an overzealous response from the immune system, which treats the non-poisonous substance as if it is poisonous. People with asthma are allergic to different triggers, such as cigarette smoke, wood smoke, pollen, dust mite or Aspergillus spores.

Men and women with asthma who are aged 20 to 40 years are most commonly affected. People with cystic fibrosis are also vulnerable. Treatment options include medications and avoiding exposure to the fungus whenever possible.

Symptoms of allergic bronchopulmonary aspergillosis

Symptoms of ABPA include:

• Wheezing
• Breathlessness
• Significant worsening of asthma symptoms
• A productive cough with brown mucus or mucus plugs
• Coughing up blood
• Loss of appetite
• Fever
• General malaise.

Complications of ABPA

Some of the complications of untreated allergic bronchopulmonary aspergillosis include:

• Haemoptysis – the irritated and inflamed airways can bleed and bloodstained phlegm is coughed up.
• Bronchiectasis – recurring bouts of inflammation eventually damage the bronchiolar walls.
• Atelectasis – this involves varying degrees of lung tissue collapse.
• Respiratory failure – the airways become obstructed, or a severe asthma attack squeezes the airways closed. This is a medical emergency.

Diagnosis of ABPA

ABPA is diagnosed using a number of tests, including:

• Chest x-rays – to check for the presence of fluid in the lungs and for any abnormalities, such as enlarged, stretched or damaged airways. CT scans may also be used.
• Skin test – the skin is pricked and a tiny amount of the allergen is introduced. A person who is allergic to Aspergillus will experience swelling, itching and reddening of the site, usually within 20 minutes. However, the skin reaction may take as long as eight hours to develop in some people.
• Blood tests – antibodies are special proteins of the immune system that are tailor-made to counter specific antigens. Blood tests check for the presence of Aspergillus antibodies (Aspergillus precipitins). These precipitins bind with the spores and form tiny solids. Around half of all people with ABPA have elevated levels of immunoglobulin E, or IgE, which is a type of blood protein that prompts allergic reactions.
• Sputum tests – Aspergillus spores are sometimes visible in the person’s mucus when viewed under a microscope. The spores can be cultured from the mucus and positively identified using special dyes.

Treatment for ABPA

There is no cure for ABPA. The condition is managed with corticosteroids taken orally or with puffers. Antifungal medications generally have no effect. People with ABPA should be monitored regularly to make sure their condition is successfully managed.

Monitoring may include checking antibody levels and evaluating the airflow capacity of the lungs. People with asthma are generally advised to avoid their known triggers whenever possible. However, Aspergillus is a particularly common fungus. People with ABPA should try to stay away from marshes, forests, bogs, compost heaps and other areas where vegetation is known to be rotting.

Where to get help

• Your GP (doctor)
• Asthma Australia Tel. 1800 278 462