How to diagnose farmer’s lung

In this Article

  • Symptoms
  • Causes
  • Diagnosis
  • Treatment

Farmer’s lung is a disease caused by an allergy to the mold in certain crops. Farmers are most likely to get it because it’s usually caused by breathing in dust from hay, corn, grass for animal feed, grain, tobacco, or some pesticides.

Not everyone gets farmer’s lung after breathing in these things. It only happens if you have an allergic reaction.

Your doctor may use another name for your condition. It’s also called extrinsic allergic alveolitis, hypersensitivity alveolitis, or hypersensitivity pneumonitis. The “-itis” at the end of these names means it causes inflammation. With farmer’s lung, the inflammation, or swelling, is in your lungs.

Symptoms

Farmer’s lung can cause three kinds of allergic reactions.

An acute attack is an intense reaction that happens 4 to 8 hours after you breathe in mold. Symptoms include:

  • Dry irritating cough
  • Fever and chills
  • Rapid breathing
  • Rapid heart rate
  • Shortness of breath
  • Sudden feeling that you’re sick

A sub-acute attack is less intense and comes on more slowly than an acute attack. Symptoms include:

  • Achy muscles and joints
  • Coughing
  • Mild fever with some chills
  • No appetite
  • Shortness of breath

Continued

You may mistake acute or sub-acute farmer’s lung for the flu, because many of the symptoms are the same.

Chronic farmer’s lung happens after you’ve had many acute attacks and are around large amounts of moldy dust often. When you reach this point, your lungs may have permanent damage. Symptoms include:

  • Cough that won’t go away
  • Depression
  • General aches and pains
  • Night sweats
  • No appetite and gradual weight loss
  • Occasional fever
  • Shortness of breath that gets worse over time
  • Weakness and loss of energy
  • Weight loss

Most people with acute or subacute farmer’s lungВ get better; only a small percentage of peopleВ develop chronic farmer’s lung. Chronic farmer’s lung symptoms can be controlled/improved, but it can’t be cured.

Farmers may notice that their symptoms get worse in the winter. Storing animal feed like hay, grass, or grain inside makes mold more likely to grow. Plus, there’s no breeze or wind to clear it out of the air.

Causes

It’s common for farmers to get this disease from moldy hay and other crops. But you also can get it from dust in things like:

  • Animal dander
  • Bacteria
  • Bark
  • Bird droppings
  • Dried rat urine
  • Feathers
  • Fungi
  • Husks
  • Insects
  • Wood

These allergens have to be very small — around 5 millionths of a meter (5 microns) — to affect you. Because the particles are so tiny, the normal defenses in your nose and throat miss them, and they go straight to your lungs. Your lungs then try to get rid of the dust, and your symptoms start when your immune system reacts to that.

Diagnosis

The most important questions your doctor will ask you will be about your environment. If you’re not a farmer, it may be harder to figure out that farmer’s lung is causing your symptoms.

It can also be hard to know what’s going on if you’re not having an acute attack. Your doctor can give you a blood test to look for certain things that trigger your immune system (called antigens) or order a chest X-ray to look for signs that you’ve had acute attacks.

Other things your doctor can do to find out if you have farmer’s lung include:

  • Pulmonary function test: This measures how much air you inhale and exhale.
  • Bronchoscopy: Your doctor uses a device called a bronchoscope to look at your airways and lungs and collect a sample of fluid for testing. You’ll be given medicine to make you sleep through this.
  • Lung biopsy: If your doctor thinks you might have farmer’s lung but can’t be sure, theyВ may want to take a sample of your lung tissue and send it to a lab for tests. You’ll probably be given medicine to sleep through this as well.

Treatment

There’s no cure for farmer’s lung, but you can control it by staying away from the allergen that causes your symptoms. You might:

  • Work outside as much as possible
  • Avoid dusty work
  • Wear a mask or other protective equipment
  • Use fans, filters, or exhaust blowers wherever you can

Steroid drugs like prednisone (Deltasone, Orasone, Meticorten) can help with your symptoms because they can slow down your immune system and help with inflammation. Your doctor may only prescribe these if you have a chronic case, though.

If steroids don’t work, your doctor may want to prescribe and immune suppressantВ such as a drug calledВ azathrioprine (Azasan).

In addition to recommending that you avoid your triggers, your doctor may also recommend bed rest or oxygen therapy, which involves getting extra oxygen through tubes in your nose or a mask, to help you feel better.

Sources

Canadian Centre for Occupational Health & Safety: “Farmer’s Lung,” “Hypersensitivity Pneumonitis (Extrinsic Allergic Alveolitis).”

Farm Safety Association: “Farmer’s Lung: It Takes Your Breath Away!”

Canadian Lung Association: “Farmer’s Lung.”

Medscape: “Farmer’s Lung.”

Virginia Tech Virginia Cooperative Extension: “Farmer’s Lung: Causes and Symptoms of Mold and Dust Induced Respiratory Illness.”

Farmer’s lung is a type of allergic reaction that occurs as a response to mold from crops and grains. For this reason, it commonly affects those who work on farms.

There are different categories of farmer’s lung (FL), depending on the level of exposure to the mold.

This article discusses how FL affects the body and the different types that can occur.

It will also explore the treatment options available and the main methods of prevention.

How to diagnose farmer's lung

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According to the American Lung Association (ALA), FL is a type of hypersensitivity pneumonitis. Hypersensitivity pneumonitis occurs when a person breathes in a substance, or the allergen, and has an allergic reaction to it.

FL occurs as a result of breathing in mold from hay, grain, and straw.

While it commonly affects farmers and cattle workers, FL can affect any person who experiences exposure to the mold.

Healthcare professionals also refer to FL as:

  • extrinsic allergic alveolitis
  • hypersensitivity alveolitis
  • hypersensitivity pneumonitis

FL occurs as a result of breathing in moldy dust, which contains microorganisms. Specifically, these are spores of bacteria that are able to tolerate heat.

The bacteria that most commonly cause FL are Micropolyspora faeni and Thermoactinomyces vulgaris.

A 2020 article notes that Aspergillus, which is a type of fungi, can also cause FL.

According to the Canadian Center for Occupational Health and Safety (CCOHS), in areas where people harvest crops in wet and rainy weather, the crops are likely to get damp and undergo “self-heating.” This allows for the heat-tolerant bacteria to grow and spoil the crops.

When they are moldy, the crops start to crumble, become dusty, and release spores. People then breathe in these spores.

The spores can trigger an allergic reaction, but not everyone will develop an allergic reaction to the spores.

The spores contain substances known as antigens, which the body’s immune system recognizes. The immune system identifies the mold spores as being foreign and produces substances known as antibodies, which fight the bacteria and fungus.

This occurs in the lungs. However, certain immune cells, such as white blood cells, will release poisons and chemicals that will damage lung tissue.

This results in the breathing and respiratory issues associated with FL. But the severity of these effects will depend on a person’s sensitivity to the mold.

The symptoms will vary depending on the person. Some people may have an abrupt, acute reaction to the substance.

Ultimately, this depends on the person’s sensitivity to the spores and how much enters the lungs.

There are three distinct types of FL: acute, sub-acute, and chronic.

Acute

According to the CCOHS, acute FL occurs in 1 in 3 cases.

It typically occurs after a person has experienced exposure to high concentrations of dust from the mold.

Symptoms of acute FL can be nonspecific and include:

  • shortness of breath
  • a low-grade fever
  • a fast heart rate
  • quick breathing
  • suddenly feeling sick
  • a dry cough

The ALA note that acute FL occurs 4–6 hours after the person breathes in the spores.

The CCOHS state that signs and symptoms usually decline after 12 hours if the person avoids repeated exposure to the moldy dust. But symptoms can last for up to 2 weeks.

Sub-acute

Sub-acute FL occurs after a person has continuously inhaled moldy dust, but not a high concentration of it.

It can be more difficult to identify, as symptoms develop more subtly. Symptoms include:

  • coughing
  • shortness of breath
  • generally feeling unwell
  • muscle and joint pain and aches
  • loss of appetite
  • weight loss over several weeks
  • low-grade fever
  • occasional chills

Chronic

Chronic FL occurs after long periods of exposure to the moldy dust. The inhaled concentration of moldy dust does not have to be high. The illness can occur over many months.

  • increasing shortness of breath
  • an occasional mild fever
  • significant weight loss
  • lack of energy

The 2020 article notes that the most important step to take is avoiding exposure to the spores.

If a person receives a diagnosis early, avoidance of the exposure may be enough to entirely reverse the damage. After a short time, a person’s lungs will return to normal.

For more severe cases, treatment can include corticosteroids and immunosuppressants. A person may need to take this medication for 3 months.

Research has shown that steroids are effective in acute FL. But there is no evidence to suggest that they are effective at preventing disease progression in the long term.

Additionally, people may require bronchodilators to make breathing easier, and oxygen therapy to raise the amount of oxygen in a person’s blood.

The CCOHS recommend not using medications long term, as doing so can hide symptoms of FL.

In cases where there is progressive disease with respiratory failure, a person may require lung transplantation.

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Diagnostic Considerations

Differential diagnosis of farmer’s lung depends on the amount, intensity, duration, and frequency of exposure and on the stage of disease at clinical presentation. Diagnostic considerations include the following:

Acute hypersensitivity pneumonitis due to farmer’s lung

Bronchoalveolar cell carcinoma

Organic dust toxic syndrome

Chronic farmer’s lung

Congestive heart failure

Desquamative interstitial pneumonitis

Respiratory bronchiolitis – Interstitial lung diseases

Toxic fume bronchiolitis (eg, caused by sulfur dioxide, nitrogen dioxide, ammonia, chlorine, phosgene, ozone)

Differential Diagnoses

References

Zergham AS, Heller D. Farmers Lung. StatPearls [Internet]. 2020 Jan. [Medline]. [Full Text].

[Guideline] Raghu G, Remy-Jardin M, Ryerson CJ, et al. Diagnosis of hypersensitivity pneumonitis in adults. An official ATS/JRS/ALAT clinical practice guideline. Am J Respir Crit Care Med. 2020 Aug 1. 202(3):e36-e69. [Medline]. [Full Text].

Lehrer SB, Turer E, Weill H, Salvaggio JE. Elimination of bagassosis in Louisiana paper manufacturing plant workers. Clin Allergy. 1978 Jan. 8(1):15-20. [Medline].

Liu S, Chen D, Fu S, et al. Prevalence and risk factors for farmer’s lung in greenhouse farmers: an epidemiological study of 5,880 farmers from Northeast China. Cell Biochem Biophys. 2015 Mar. 71(2):1051-7. [Medline].

Barrera C, Millon L, Rognon B, et al. Immunoreactive proteins of Saccharopolyspora rectivirgula for farmer’s lung serodiagnosis. Proteomics Clin Appl. 2014 Dec. 8(11-12):971-81. [Medline].

Ashitani J, Kyoraku Y, Yanagi S, Matsumoto N, Nakazato M. Elevated levels of beta-D-glucan in bronchoalveolar lavage fluid in patients with farmer’s lung in Miyazaki, Japan. Respiration. 2008. 75(2):182-8. [Medline].

Deschenes D, Provencher S, Cormier Y. Farmer’s lung-induced hypersensitivity pneumonitis complicated by shock. Respir Care. 2012 Mar. 57(3):464-6. [Medline].

Bellanger AP, Reboux G, Botterel F, et al. New evidence of the involvement of Lichtheimia corymbifera in farmer’s lung disease. Med Mycol. 2010 Nov. 48(7):981-7. [Medline].

Barrera C, Valot B, Rognon B, Zaugg C, Monod M, Millon L. Draft genome sequence of the principal etiological agent of farmer’s lung disease, Saccharopolyspora rectivirgula. Genome Announc. 2014 Dec 18. 2(6):[Medline]. [Full Text].

[Guideline] Dobashi K, Akiyama K, Usami A, et al, for the Committee for Japanese Guideline for Diagnosis and Management of Occupational Allergic Disease, The Japanese Society of Allergology. Japanese guidelines for occupational allergic diseases 2017. Allergol Int. 2017 Apr. 66(2):265-80. [Medline]. [Full Text].

Cardoso J, Carvalho I. The value of family history in the diagnosis of hypersensitivity pneumonitis in children. J Bras Pneumol. 2014 Mar-Apr. 40(2):183-7. [Medline]. [Full Text].

Hanak V, Golbin JM, Ryu JH. Causes and presenting features in 85 consecutive patients with hypersensitivity pneumonitis. Mayo Clin Proc. 2007 Jul. 82(7):812-6. [Medline].

Barber CM, Wiggans RE, Carder M, Agius R. Epidemiology of occupational hypersensitivity pneumonitis; reports from the SWORD scheme in the UK from 1996 to 2015. Occup Environ Med. 2017 Jul. 74(7):528-30. [Medline]. [Full Text].

Liu S, Chen D, Fu S, et al. Prevalence and risk factors for farmer’s lung in greenhouse farmers: an epidemiological study of 5,880 farmers from Northeast China. Cell Biochem Biophys. 2015 Mar. 71(2):1051-7. [Medline].

Barbee RA, Callies Q, Dickie HA, Rankin J. The long-term prognosis in farmer’s lung. Am Rev Respir Dis. 1968 Feb. 97(2):223-31. [Medline].

Ohtsuka Y, Munakata M, Tanimura K, et al. Smoking promotes insidious and chronic farmer’s lung disease, and deteriorates the clinical outcome. Intern Med. 1995 Oct. 34(10):966-71. [Medline].

Soumagne T, Chardon ML, Dournes G, et al. Emphysema in active farmer’s lung disease. PLoS One. 2017. 12(6):e0178263. [Medline]. [Full Text].

Roussel S, Reboux G, Dalphin JC, Laplante JJ, Piarroux R. Evaluation of salting as a hay preservative against farmer’s lung disease agents. Ann Agric Environ Med. 2005. 12(2):217-21. [Medline].

Cormier Y, Belanger J. The fluctuant nature of precipitating antibodies in dairy farmers. Thorax. 1989 Jun. 44(6):469-73. [Medline].

Kern RM, Singer JP, Koth L, et ak. Lung transplantation for hypersensitivity pneumonitis. Chest. 2015 Jun. 147(6):1558-65. [Medline]. [Full Text].

How to diagnose farmer's lung

Extrinsic allergic alveolitis; Farmer’s lung; Mushroom picker’s disease; Humidifier or air-conditioner lung; Bird breeder’s or bird fancier’s lung

Hypersensitivity pneumonitis is inflammation of the lungs due to breathing in a foreign substance, usually certain types of dust, fungus, or molds.


Causes

Hypersensitivity pneumonitis usually occurs in people who work in places where there are high levels of organic dusts, fungus, or molds.

Long-term exposure can lead to lung inflammation and acute lung disease. Over time, the acute condition turns into long-lasting (chronic) lung disease.

Hypersensitivity pneumonitis may also be caused by fungi or bacteria in humidifiers, heating systems, and air conditioners found in homes and offices. Exposure to certain chemicals, such as isocyanates or acid anhydrides, can also lead to hypersensitivity pneumonitis.

Examples of hypersensitivity pneumonitis include:

Bird fancier’s lung: This is the most common type of hypersensitivity pneumonitis. It is caused by repeated or intense exposure to proteins found in the feathers or droppings of many species of birds.

Farmer’s lung: This type of hypersensitivity pneumonitis is caused by exposure to dust from moldy hay, straw, and grain.


Symptoms

Symptoms of acute hypersensitivity pneumonitis often occur 4 to 6 hours after you have left the area where the offending substance is found. This makes it difficult to find a connection between your activity and the disease. Symptoms might resolve before you go back to the area where you encountered the substance. In the chronic phase of the condition, the symptoms are more constant and are less affected by exposure to the substance.

Symptoms may include:

  • Chills
  • Cough
  • Fever
  • Malaise (feeling ill)
  • Shortness of breath

Symptoms of chronic hypersensitivity pneumonitis may include:

  • Breathlessness, especially with activity
  • Cough, often dry
  • Loss of appetite
  • Unintentional weight loss


Exams and Tests

The health care provider will perform a physical examination and ask about your symptoms.

Your provider may hear abnormal lung sounds called crackles (rales) when listening to your chest with a stethoscope.

Lung changes due to chronic hypersensitivity pneumonitis may be seen on a chest x-ray. Other tests may include:

  • Aspergillosis precipitin blood test to check if you’ve been exposed to the aspergillus fungus
  • Bronchoscopy with washings, biopsy, and bronchoalveolar lavage
  • Complete blood count (CBC)
  • CT scan of the chest
  • Hypersensitivity pneumonitis antibody blood test
  • Krebs von den Lungen-6 assay (KL-6) blood test
  • Pulmonary function tests
  • Surgical lung biopsy

Related Tags

  • Antibody
  • Aspergillosis precipitin
  • Breathing difficulty
  • Bronchoscopy
  • CBC blood test
  • Chest CT
  • Chest x-ray
  • Fatigue
  • Interstitial lung disease
  • Lung disease
  • Open lung biopsy
  • Pulmonary function tests


Treatment

First, the offending substance must be identified. Treatment involves avoiding this substance in the future. Some people may need to change jobs if they cannot avoid the substance at work.

If you have a chronic form of this disease, your doctor may recommend that you take glucocorticoids (anti-inflammatory medicines). Sometimes, treatments used for asthma can help people with hypersensitivity pneumonitis.


Outlook (Prognosis)

Most symptoms go away when you avoid or limit your exposure to the material that caused the problem. If prevention is made in the acute stage, the outlook is good. When it reaches the chronic stage, the disease might continue to progress, even if the offending substance is avoided.


Possible Complications

The chronic form of this disease may lead to pulmonary fibrosis. This is a scarring of the lung tissue that often is not reversible. Eventually, end-stage lung disease and respiratory failure can occur.


When to Contact a Medical Professional

Call your provider if you develop symptoms of hypersensitivity pneumonitis.


Prevention

The chronic form can be prevented by avoiding the material that causes the lung inflammation.

Patterson KC, Rose CS. Hypersensitivity pneumonitis. In: Broaddus VC, Mason RJ, Ernst JD, et al, eds. Murray and Nadel’s Textbook of Respiratory Medicine. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 64.

Tarlo SM. Occupational lung disease. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 87.

How to diagnose farmer's lung

Extrinsic allergic alveolitis; Farmer’s lung; Mushroom picker’s disease; Humidifier or air-conditioner lung; Bird breeder’s or bird fancier’s lung

Hypersensitivity pneumonitis is inflammation of the lungs due to breathing in a foreign substance, usually certain types of dust, fungus, or molds.


Causes

Hypersensitivity pneumonitis usually occurs in people who work in places where there are high levels of organic dusts, fungus, or molds.

Long-term exposure can lead to lung inflammation and acute lung disease. Over time, the acute condition turns into long-lasting (chronic) lung disease.

Hypersensitivity pneumonitis may also be caused by fungi or bacteria in humidifiers, heating systems, and air conditioners found in homes and offices. Exposure to certain chemicals, such as isocyanates or acid anhydrides, can also lead to hypersensitivity pneumonitis.

Examples of hypersensitivity pneumonitis include:

Bird fancier’s lung: This is the most common type of hypersensitivity pneumonitis. It is caused by repeated or intense exposure to proteins found in the feathers or droppings of many species of birds.

Farmer’s lung: This type of hypersensitivity pneumonitis is caused by exposure to dust from moldy hay, straw, and grain.


Symptoms

Symptoms of acute hypersensitivity pneumonitis often occur 4 to 6 hours after you have left the area where the offending substance is found. This makes it difficult to find a connection between your activity and the disease. Symptoms might resolve before you go back to the area where you encountered the substance. In the chronic phase of the condition, the symptoms are more constant and are less affected by exposure to the substance.

Symptoms may include:

  • Chills
  • Cough
  • Fever
  • Malaise (feeling ill)
  • Shortness of breath

Symptoms of chronic hypersensitivity pneumonitis may include:

  • Breathlessness, especially with activity
  • Cough, often dry
  • Loss of appetite
  • Unintentional weight loss


Exams and Tests

The health care provider will perform a physical examination and ask about your symptoms.

Your provider may hear abnormal lung sounds called crackles (rales) when listening to your chest with a stethoscope.

Lung changes due to chronic hypersensitivity pneumonitis may be seen on a chest x-ray. Other tests may include:

  • Aspergillosis precipitin blood test to check if you’ve been exposed to the aspergillus fungus
  • Bronchoscopy with washings, biopsy, and bronchoalveolar lavage
  • Complete blood count (CBC)
  • CT scan of the chest
  • Hypersensitivity pneumonitis antibody blood test
  • Krebs von den Lungen-6 assay (KL-6) blood test
  • Pulmonary function tests
  • Surgical lung biopsy

Related Tags

  • Antibody
  • Aspergillosis precipitin
  • Breathing difficulty
  • Bronchoscopy
  • CBC blood test
  • Chest CT
  • Chest x-ray
  • Fatigue
  • Interstitial lung disease
  • Lung disease
  • Open lung biopsy
  • Pulmonary function tests


Treatment

First, the offending substance must be identified. Treatment involves avoiding this substance in the future. Some people may need to change jobs if they cannot avoid the substance at work.

If you have a chronic form of this disease, your doctor may recommend that you take glucocorticoids (anti-inflammatory medicines). Sometimes, treatments used for asthma can help people with hypersensitivity pneumonitis.


Outlook (Prognosis)

Most symptoms go away when you avoid or limit your exposure to the material that caused the problem. If prevention is made in the acute stage, the outlook is good. When it reaches the chronic stage, the disease might continue to progress, even if the offending substance is avoided.


Possible Complications

The chronic form of this disease may lead to pulmonary fibrosis. This is a scarring of the lung tissue that often is not reversible. Eventually, end-stage lung disease and respiratory failure can occur.


When to Contact a Medical Professional

Call your provider if you develop symptoms of hypersensitivity pneumonitis.


Prevention

The chronic form can be prevented by avoiding the material that causes the lung inflammation.

Patterson KC, Rose CS. Hypersensitivity pneumonitis. In: Broaddus VC, Mason RJ, Ernst JD, et al, eds. Murray and Nadel’s Textbook of Respiratory Medicine. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 64.

Tarlo SM. Occupational lung disease. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 87.

Affiliations

  • 1 Grupo Gallego Multidisciplinar de Enfermedades Pulmonares Intersticiales Difusas (GAMEPID), Sociedad Gallega de Patología Respiratoria (SOGAPAR), España. Electronic address: [email protected]
  • 2 Grupo Gallego Multidisciplinar de Enfermedades Pulmonares Intersticiales Difusas (GAMEPID), Sociedad Gallega de Patología Respiratoria (SOGAPAR), España.
  • PMID: 26874898
  • DOI: 10.1016/j.arbres.2015.12.001
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Authors

Affiliations

  • 1 Grupo Gallego Multidisciplinar de Enfermedades Pulmonares Intersticiales Difusas (GAMEPID), Sociedad Gallega de Patología Respiratoria (SOGAPAR), España. Electronic address: [email protected]
  • 2 Grupo Gallego Multidisciplinar de Enfermedades Pulmonares Intersticiales Difusas (GAMEPID), Sociedad Gallega de Patología Respiratoria (SOGAPAR), España.
  • PMID: 26874898
  • DOI: 10.1016/j.arbres.2015.12.001

Abstract

Farmer’s lung disease (FLD) is a form of hypersensitivity pneumonitis (HP) caused by inhaling microorganisms from hay or grain stored in conditions of high humidity in the agricultural workplace. It is probably underdiagnosed, especially in northern Spain, where climatic conditions favor the development of this disease. According to previous studies, the most common antigens are usually thermophilic actinomycetes and fungi. The epidemiology of the disease is not well known, and is based on studies conducted by Central European and Asian groups. The clinical presentation may vary, differentiating the chronic (exposure to lower concentrations of the antigen over a longer period time) and the acute forms (after exposure to high concentrations of the antigen). In patients with respiratory symptoms and agricultural occupational exposure, radiological, lung function and/or anatomical pathology findings must be compatible with FLD, bronchoalveolar lavage must show lymphocytosis, and tests must find sensitivity to the antigen. The main treatment is avoidance of the antigen, so it is essential to educate patients on preventive measures. To date, no controlled studies have assessed the role of immunosuppressive therapy in this disease. Corticosteroid treatment has only been shown to accelerate resolution of the acute forms, but there is no evidence that it is effective in preventing disease progression in the long-term or reducing mortality.

Keywords: Diffuse interstitial lung disease; Enfermedad del pulmón de granjero; Enfermedad pulmonar intersticial difusa; Farmer’s lung disease; Hypersensitivity pneumonitis; Neumonitis por hipersensibilidad.

How to diagnose farmer's lung

Use the following format to cite this article:

Respiratory illnesses associated with agriculture. (2012) Farm and Ranch eXtension in Safety and Health (FReSH) Community of Practice. Retrieved from http://www.extension.org/pages/63439/respiratory-illnesses-associated-with-agriculture.

A farmer’s or rancher’s life is not always associated with the great outdoors and fresh air. In production agriculture, farmers and ranchers can be exposed to toxic gases and contaminated particulate matter that can cause short- and long-term health problems. The three main respiratory illnesses associated with production agriculture are:

  • farmer’s lung,
  • silo filler’s disease, and
  • organic dust toxicity syndrome.

Farmer’s Lung

Farmer’s lung, or farmer’s hypersensitivity pneumonitis (FHP), is a noninfectious allergic disease that affects normal lung function. It results from the inhalation of mold spores from moldy hay, straw, or grain. The mold spores that cause farmer’s lung are microorganisms that grow in baled hay, stored grain, or silage with high moisture content (30%). Exposure to mold spores is greater in late winter and early spring.

Mold spores, which are not always visible, are so tiny that 250,000 spores can fit on the head of a pin. Because the spores are so small, it is easy for a farmer or rancher to breathe in millions of spores in a few minutes. Due to their size, the mold spores easily move into and settle in the lower part of the lungs.

Symptoms usually begin four to six hours after exposure to mold spores and can include increased coughing, coughs that bring up mucus, fever, chills, shortness of breath, discomfort in the lungs, and a tightness and/or pain in the chest. Symptoms may become most severe from 12 to 48 hours after exposure.

Allergic reaction to mold spores can be acute or chronic. An acute attack typically resembles the flu or pneumonia. Chronic reactions can resemble a nagging chest cold. A producer who has been diagnosed with farmer’s lung should avoid additional exposure to mold spores; otherwise, the producer’s condition could worsen and render him or her inactive. In some cases, farmer’s lung can be fatal.

If you think that you may have farmer’s lung, contact your physician and explain your symptoms and occupation. If your physician is not familiar with farmer’s lung, you may need to request a referral to a specialist for testing, diagnosis, and treatment.

To reduce the risk of contracting farmer’s lung, take the following steps:

  • Identify and minimize contaminants in your work environment.
  • Avoid exposure to contaminants and mold spores.
  • Limit the growth of mold spores by using mold inhibitors.
  • Harvest, bale, store, and ensile grains at the recommended moisture level to reduce mold growth.
  • Convert from a manual to a mechanical or automated feeding or feed-handling system to reduce the release of airborne mold spores.
  • Move work outside and avoid dusty work in confined areas whenever possible.
  • Mechanically remove air contaminants through ventilation with fans, exhaust blowers, and so on.
  • Wear appropriate respirators, dust masks, or other personal protective equipment (PPE). Click here to learn more about respiratory PPE.

Silo Filler’s Disease

Silo filler’s disease results from inhaling nitrogen dioxide, a silo gas produced during the silage fermentation process. Although a producer who has been exposed to silo gases may not experience symptoms, damage to the lungs may still have occurred. Fluid can build up in a person’s lungs 12 hours after exposure to nitrogen dioxide. Cough, hemoptysis (coughing up blood from the respiratory tract), dyspnea (shortness of breath), and chest pain can occur after an exposure to 20 ppm, a moderate level of nitrogen dioxide. This concentration has been designated by the National Institute for Occupational Safety and Health (NIOSH) as immediately dangerous to life and health (IDLH). Exposure to higher concentrations (greater than 100 ppm) can result in pulmonary edema (fluid accumulation in the lungs) and in swelling in the lungs, leading to long-term respiratory problems or death. Lower concentrations of 15 to 20 ppm are considered dangerous and can cause respiratory impairment.

If you have been exposed to silo gases, even a small amount, seek immediate medical attention.

To reduce exposure to nitrogen dioxide in silo gases, refrain from entering a silo for ten days to three weeks after filling is complete. If entry is necessary after the three-week period, run the silo blower for a minimum of 30 minutes prior to and during entry, and use a portable gas monitor to continually monitor the gas and oxygen levels in the silo. Click here to learn more about silo gases and how to reduce the risk of exposure.

Organic Dust Toxicity Syndrome

Organic Dust Toxicity Syndrome (ODTS), also called grain fever, toxic alveolitis, or pulmonary mycotoxicosis, is caused by exposure to very large amounts of organic dust. Certain agricultural areas may have large amounts of organic dust: grain storage, hog barns, poultry barns, and cotton-processing areas.

The onset of ODTS can occur four to six hours after exposure, and symptoms can be similar to those of acute farmer’s lung and may include cough, fever, chills, fatigue, muscle pain, and loss of appetite. People who have experienced ODTS and who experience additional exposures to organic dust have an increased risk for respiratory problems and the potential for developing chronic bronchitis. Producers can become very sick from ODTS, but most people completely recover. Occurrences of ODTS are underreported because symptoms often resemble the flu or other mild illnesses.

You can reduce your risk of contracting ODTS by using a respirator to decrease exposure to organic dust. Click here to learn about the different types of respirators used in production agriculture. Implement best management practices to maintain good air quality in confinement buildings for swine and poultry.

How to diagnose farmer's lung

Extrinsic allergic alveolitis; Farmer’s lung; Mushroom picker’s disease; Humidifier or air-conditioner lung; Bird breeder’s or bird fancier’s lung

Hypersensitivity pneumonitis is inflammation of the lungs due to breathing in a foreign substance, usually certain types of dust, fungus, or molds.


Causes

Hypersensitivity pneumonitis usually occurs in people who work in places where there are high levels of organic dusts, fungus, or molds.

Long-term exposure can lead to lung inflammation and acute lung disease. Over time, the acute condition turns into long-lasting (chronic) lung disease.

Hypersensitivity pneumonitis may also be caused by fungi or bacteria in humidifiers, heating systems, and air conditioners found in homes and offices. Exposure to certain chemicals, such as isocyanates or acid anhydrides, can also lead to hypersensitivity pneumonitis.

Examples of hypersensitivity pneumonitis include:

Bird fancier’s lung: This is the most common type of hypersensitivity pneumonitis. It is caused by repeated or intense exposure to proteins found in the feathers or droppings of many species of birds.

Farmer’s lung: This type of hypersensitivity pneumonitis is caused by exposure to dust from moldy hay, straw, and grain.


Symptoms

Symptoms of acute hypersensitivity pneumonitis often occur 4 to 6 hours after you have left the area where the offending substance is found. This makes it difficult to find a connection between your activity and the disease. Symptoms might resolve before you go back to the area where you encountered the substance. In the chronic phase of the condition, the symptoms are more constant and are less affected by exposure to the substance.

Symptoms may include:

  • Chills
  • Cough
  • Fever
  • Malaise (feeling ill)
  • Shortness of breath

Symptoms of chronic hypersensitivity pneumonitis may include:

  • Breathlessness, especially with activity
  • Cough, often dry
  • Loss of appetite
  • Unintentional weight loss


Exams and Tests

The health care provider will perform a physical examination and ask about your symptoms.

Your provider may hear abnormal lung sounds called crackles (rales) when listening to your chest with a stethoscope.

Lung changes due to chronic hypersensitivity pneumonitis may be seen on a chest x-ray. Other tests may include:

  • Aspergillosis precipitin blood test to check if you’ve been exposed to the aspergillus fungus
  • Bronchoscopy with washings, biopsy, and bronchoalveolar lavage
  • Complete blood count (CBC)
  • CT scan of the chest
  • Hypersensitivity pneumonitis antibody blood test
  • Krebs von den Lungen-6 assay (KL-6) blood test
  • Pulmonary function tests
  • Surgical lung biopsy

Related Tags

  • Antibody
  • Aspergillosis precipitin
  • Breathing difficulty
  • Bronchoscopy
  • CBC blood test
  • Chest CT
  • Chest x-ray
  • Fatigue
  • Interstitial lung disease
  • Lung disease
  • Open lung biopsy
  • Pulmonary function tests


Treatment

First, the offending substance must be identified. Treatment involves avoiding this substance in the future. Some people may need to change jobs if they cannot avoid the substance at work.

If you have a chronic form of this disease, your doctor may recommend that you take glucocorticoids (anti-inflammatory medicines). Sometimes, treatments used for asthma can help people with hypersensitivity pneumonitis.


Outlook (Prognosis)

Most symptoms go away when you avoid or limit your exposure to the material that caused the problem. If prevention is made in the acute stage, the outlook is good. When it reaches the chronic stage, the disease might continue to progress, even if the offending substance is avoided.


Possible Complications

The chronic form of this disease may lead to pulmonary fibrosis. This is a scarring of the lung tissue that often is not reversible. Eventually, end-stage lung disease and respiratory failure can occur.


When to Contact a Medical Professional

Call your provider if you develop symptoms of hypersensitivity pneumonitis.


Prevention

The chronic form can be prevented by avoiding the material that causes the lung inflammation.

Patterson KC, Rose CS. Hypersensitivity pneumonitis. In: Broaddus VC, Mason RJ, Ernst JD, et al, eds. Murray and Nadel’s Textbook of Respiratory Medicine. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 64.

Tarlo SM. Occupational lung disease. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 87.