Farmer’s Lung

Air that farmers breathe is contaminated with toxic gases or particulate matter that is dangerous. Continuous exposure to these contaminants leads to the condition called farmer’s lung.

Farmer’s lung is a hypersensitivity allergy reaction that is caused by breathing in dust from moldy hay, grain handling, feed handling and livestock confinement systems or other agricultural products.

The hypersensitive inflammatory response in farmer’s lung can become a chronic condition that is dangerous. Initially disease starts as sudden attack or slow progressive disease and it causes breathing problems. Avoiding the exposure to dust and moldy crops is beneficial but long term exposure causes permanent damage to lung causing physical disability or even death.

The degree of risk depends on how much amount is collected in person’s lungs. Working with loose hay in open field is less dangerous while working indoors a farmer inhales large amount of dust within a short period of time.

Age/sex prevalence of Farmer's lung

Children rarely develop farmer’s lung as Farmer’s lung is a risk for adults who breathe dust from moldy hay.

Classification of Farmer's lung
• Acute farmer’s lung:

Acute farmer’s lung starts as an acute attack within 4-8 hours when a person breathes a large amount of dust from moldy crop.
Signs and symptoms subside after 12 hours of avoiding the exposure to moldy dust but it can last up to 2 weeks. Severe attack can last as long as 12 weeks.

• Sub-acute farmer’s lung:

Sub acute farmer’s lung is more common as compared to acute farmer’s lung. Sub acute farmer’s lung is more difficult to notice as it is less intense. It develops slowly from continual exposure to small amount of hay. Sub acute farmer’s lung mimics common chest cold and remains throughout winters. Some people lose weight over several weeks.

• Chronic farmer’s lung:

Chronic farmer’s lung develops slowly over a period of year after several acute attacks. Persons who are in continuous exposure to moldy dust are at great risk.

Cause of Farmer's lung
Heat tolerating bacteria and moulds are found in moldy crops. Moulds called “Aspergillus” are main causes of farmer’s lung. In certain areas where crops are harvested in wet and rainy weather, crops undergo self heating in storage; in this case heat tolerating bacteria and moulds grow rapidly and cause spoilage. This spoiled hay when breathed the spores enter the innermost region of lungs and problems arises. Inhaled spores trigger an allergic reaction.

When a person inhales a large amount of dust and spores, the immune system produces antibodies against that antigen. Once the antibodies are produced a person becomes sensitive to that allergen. On further exposure to moldy dust generates a hypersensitive type of allergic reaction.

Signs and symptoms of Farmer's lung
The signs and symptoms of acute farmer’s lung:
- Shortness of breath.
- Dry cough.
- General sick feeling.
- Increased heart rate.
- Rapid breathing.

The signs and symptoms of sub acute farmer’s lung:
- Cough.
- Muscle and joint pain.
- Shortness of breath.
- General sick feeling.
- Loss of appetite and weight.

Signs and symptoms of chronic farmer’s lung include:
- Shortness of breath.
- Occasional mild fever.
- Lack of energy.
- Marked loss of weight.
- Permanent lung damage.

Investigation of Farmer's lung
History of exposure confirms the diagnosis. There is development of signs and symptoms within 4-8 hours of exposure to dust form moldy crop.
• Lung x-ray
• Blood test for antibodies
• Pulmonary lavage test is done examine contents in small area of lung.
• Lung function test.
• Lung biopsy.
• Lung allergy challenge test.

Treatment of Farmer's lung
• First step is to avoid exposure to moldy dust.
• Bed rest and oxygen therapy is needed in serious cases.
• Long term of medication is not recommended as symptoms subside without curing the damage of lung damage.

Prevention of Farmer's lung
Steps should be followed to avoid spoilage of crop and production of spores that cause allergic reaction. Following measures are advised.
• Wet crops can be dried at harvest.
• If there is high risk of spoiling of crop it should be stored in silage instead of bales, if possible.
• Farms should be mechanized as much as possible to reduce exposure.
• During cleaning of barns crop should be wetted down to prevent it from being airborne.

Prognosis of Farmer's lung
Person who becomes hypersensitive to moldy dust remains hypersensitive for years or perhaps for life.

Complications of Farmer's lung
• Scarring of lung.
• Pulmonary fibrosis.
• Emphysema.
• Death due to pulmonary insufficiency.
• Death due to cor pulmonale.
• Respiratory failure.

Differential diagnosis of Farmer's lung
• Asthma
• Emphysema.
• Cystic fibrosis.
• Smoker’s cough.
• Chronic pneumonia.
• Mesothelioma.
• Chronic bronchitis.

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