Did you know farmer’s lung is a respiratory allergic lung disease that affects farm workers handling hay or other plant materials contaminated with mould and actinomycetes?
Did you know a single gram (dry weight) of hay could contain up to 102,000,000 (102 million) fungal spores and 1,200,000,000 (i.e., 1200 million) actinomycete spores?
Did you know that up to 1,600,000,000 (i.e.,1600 million) spores per cubic meter of air have been recorded in farm buildings while hay was being shaken for animals?
And did you know that on average a female worker performing yardwork inhales 18 liters of air per minute while a male worker inhales 29 liters per minute? That means a female worker in a farm building could be inhaling 1,728 million spores per hour while a male could be inhaling 2,784 million spores per hour!
Farmer’s lung is an allergic non-infectious disease. Farmer’s lung is caused by the inhalation of heat-tolerating bacteria or moulds such as Aspergillus species in decomposing compost, hay, or sugar cane. Exposure to large quantities of contaminated hay is the most common source. Exposure most commonly occurs during the winter months due to the cold, damp climate. For reasons that are not known, only a small number of exposed people actually develop the farmer’s lung disease. Exposure does not always mean disease. A study conducted in Wisconin in the USA estimated that only 4 out of every 1000 exposed farmers developed the disease. This is probably because of different immune systems in different people’s lungs. Bird Fancier’s Lung is seen in people who keep or breed domestic birds, such as pigeons. Again, for reasons unknown, only a small number of exposed people actually develop the disease.
Similar to other allergic reactions, farmer’s Lung develops in two steps. The first time a person inhales a large amount of dust and spores from mouldy hay or dust, the immune system often responds by producing specific antibodies against the antigens. Antibodies are chemicals that circulate in the blood and attack specific antigens. Once the body has produced these antibodies, there is a chance that further exposure to moldy dust can generate a hypersensitive type of allergic reaction. This reaction is typical of Farmer’s Lung. Symptoms often spontaneously resolve within 12 hours to days if antigen exposure is eliminated or avoided. Acute farmer’s lung manifests as new onset of fever, chills, nonproductive cough, chest tightness, dyspnea, headache, and malaise. If the inhalational exposure is large, patients may develop acute respiratory failure. Acute farmer’s lung is the short-term form of the disease. Farmers typically develop chronic farmer’s lung due to repeated exposure to mold spores over time, usually because they continue to ignore the symptoms of acute farmer’s lung. However, it is possible to develop chronic farmer’s lung even after one acute attack.
Farmer’s lung allergic reactions that are acute are usually treated with medication and mould avoidance. However, chronic symptoms, such as weight loss, fatigue, prolonged fever and severe difficulties in breathing, may warrant hospitalization. Severe symptoms of farmer’s require treatment with oxygen therapy, bed rest and large doses of corticosteroid medications. Farmer’s lung is more frequent in men and in the age group 51-55 years. Many farmers are forced to leave their occupation due to the physical limitations caused by farmer’s lung.
Farmer’s lung is only one of the respiratory hazards for farmers, but it is a serious one. The number of farmers affected has also been increasing in recent years. This results from a growing awareness among farmers and that they have been seeing their physicians more frequently.