Farmer's lung, as a separate clinical entity, is one of the subtypes of hypersensitivity pneumonitis (HP), an autoimmune-mediated disorder of the lung parenchyma [1] [2]. The pathogenesis starts with inhalation of dust from hay or grain containing thermophilic microorganisms (temperatures between 40-60 degrees celsius are optimal for their growth), most commonly occurring under two circumstances - in late winter months when farmers handle very large quantities of hay for feeding purposes; and in very damp and humid conditions (from heavy rain), which are favorable for thermophilic microbial growth [1] [3]. Thermoactinomyces species (T. sacchari, T. vulgaris, T. viridis) and Saccharopolyspora rectivirgula are notable bacterial pathogens, whereas several fungal species (Aspergillus and Penicillium) have been linked to farmer's lung as well [1] [4]. When these microorganisms are inhaled, a hypersensitivity reaction leads to the formation of antigen-antibody immune complexes and the appearance of symptoms [1]. On the basis of several factors (severity of exposure, duration, etc.), three distinct clinical courses have been described [1] [2] [5]:

• Acute - After severe exposure to very large quantities of microorganisms, respiratory symptoms in the form of rapidly progressing dyspnea with a cough appear within several hours and are sometimes accompanied by fever and malaise [1] [5]. Resolution of symptoms is seen after a period of several days [6]. Recurrences of the acute form of farmer's lung have been described in patients with preexisting chronic obstructive pulmonary disease (COPD) [6].
• Subacute - A somewhat less severe clinical course is encountered in the subacute form of farmer's lung, characterized by general malaise, asthenia, anorexia, dyspnea and cough [1] [5].
• Chronic - Prolonged exposure to lower concentrations results in chronic and insidious symptoms. Chronic farmer's lung, which may last for weeks or months, manifests as a slowly progressive dyspnea on exertion, a dry cough, together with weight loss, fatigue, and digital clubbing [1] [5].

• Fever

  Furthermore, his disease does not fit the entities known as grain fever and organic dust toxic syndrome. We believe that this patient presented a different entity that we coined "farmer's fever." [ncbi.nlm.nih.gov]

  Doctors diagnose patients with Farmer's lung under the following conditions: Patient exhibit a clinical history of symptoms such as cough, fever, and labored breathing when exposed to mold in work environment. [en.wikipedia.org]

  So tell your doctor about any symptoms like breathing problems, chills and fevers. Keep hay, grains and other organic materials dry as fungal spores can only grow in moist conditions. Last updated: 5th February, 2019 [farmerhealth.org.au]

  These are some of the signs and symptoms: shortness of breath, a dry irritating cough, a sudden general feeling of sickness, fever and chills, a rapid heart rate, and rapid breathing. [ccohs.ca]

• Fatigue

  Abstract A boy and a girl, 10 weeks and 3 years of age, respectively, were admitted to our department with low temperature, dry cough, fatigue and weight loss. [ncbi.nlm.nih.gov]

  The loss of energy and fatigue is due to the lack of oxygen getting to all parts of the body, as the exchange of gases in the lungs becomes less and less efficient. [ohiofarmer.com]

  Chronic farmer's lung, which may last for weeks or months, manifests as a slowly progressive dyspnea on exertion, a dry cough, together with weight loss, fatigue, and digital clubbing. [symptoma.com]

  Clubbing Generalized fatigue Causes of Farmer’s Lungs Farmer’s lung is not an infectious condition. Pneumonitis refers to any type of lung inflammation and includes pneumonia, a term usually reserved for a lung infection. [healthhype.com]

• Exposure to Moldy Hay

  Asymptomatic farmers (n = 12) and normal volunteers with no prior exposure to moldy hay (n = 15) were used as control subjects. [ncbi.nlm.nih.gov]

  As the exposure to this moldy hay becomes chronic, symptoms of respiratory illness start to surface. [epainassist.com]

  Usually, people with Farmer's Lung do not associate their health problem with exposure to moldy hay. Instead, they go to their doctors complaining of breathing problems. [ccohs.ca]

• Pneumonia

  After bed rest, I regained my energy and thought I had licked the pneumonia. A bump in the road After getting back into farm activities, I accidentally inhaled a large quantity of dust and experienced an abrupt case of pneumonia-like symptoms again. [ohiofarmer.com]

  Among them the immediate cause of death was pneumonia in seven patients, respiratory insufficiency in four, and pneumothorax in one patient. [ncbi.nlm.nih.gov]

  Symptoms appear 4-8 hours after exposure and may resemble anything from a cold to pneumonia. Scar tissue forms permanently in the lungs. [extension.missouri.edu]

  Pneumonitis refers to any type of lung inflammation and includes pneumonia, a term usually reserved for a lung infection. [healthhype.com]

• Dyspnea

  Depending on the severity of exposure, patients can suffer from acute, subacute, or chronic respiratory (dyspnea, cough) and constitutional symptoms, as well as fever. [symptoma.com]

  A 70-year-old nonsmoking woman with dyspnea on exercise was referred for surgical resection of a large bulla in the lung. [ncbi.nlm.nih.gov]

  Later these may be followed by fever, chills, productive cough, headache, perspiration, foul-smelling sputum, and sometimes dyspnea. [medical-dictionary.thefreedictionary.com]

• Pulmonary Disorder

  Definition of farmer's lung : an acute pulmonary disorder characterized by sudden onset, fever, cough, expectoration, and breathlessness that results from the inhalation of spores in dust from moldy hay or straw First Known Use of farmer's lung 1945, [merriam-webster.com]

  Farmer’s lung, also called thresher’s lung or harvester’s lung, a pulmonary disorder that results from the development of hypersensitivity to inhaled dust from moldy hay or other fodder. [britannica.com]

  Hypersensitivity pneumonitis (HP), also known as extrinsic allergic alveolitis, represents a group of pulmonary disorders mediated by an inflammatory reaction to inhalation of an allergen. [radiopaedia.org]

• Rales

  The clinical features were fatigability, weight loss, recurrent fever, dry cough, pulmonary rales, and clubbing. Serologic studies for precipitins to Micropolyspora faeni were positive. [ncbi.nlm.nih.gov]

  […] hay, an ideal growth medium for the fungi– Microspora vulgaris, Thermoactinomyces vulgaris, and Micropolyspora faeni— implicated in FL Clinical Attacks of several days duration from May to October–the growing season in the Northern Hemisphere, causing rales [medical-dictionary.thefreedictionary.com]

• Nausea

  There are acute attacks of fever, nausea, breathlessness and cough a few hours after exposure. [medical-dictionary.thefreedictionary.com]

  Nausea has been reported within 10 hours post-exposure. The chronic form of the disease has an onset over months with increased fatigue and weight loss. A more recent and much rarer manifestation is the presence of large bulla in the lung [24]. [oatext.com]

• Sweating

  Symptoms include: shortness of breath upon exertion, chronic coughing, physical weakness, occasional fever and sweating, decrease in appetite, aches and pains. Chronic Stage: Debilitating effects are now considered long-term. [en.wikipedia.org]

  Then that night will feel realy cold, but then wake and heavy sweating. And norm bad sleep too. A mask like this I got U I feel a bit panicky in a mask. [thefarmingforum.co.uk]

  Symptoms of chronic Farmer’s Lung include the same problems with the addition of night sweats, fatigue, decreased appetite and weight loss. Some people are immune to the condition, but there is no way of knowing who is likely to be affected. [thatsfarming.com]

  Typical Symptoms: progressively increasing severe shortness of breath with any exertion chronic coughing physical weakness occasional fever and sweating at night appetite depression general aches and pains How to Prevent or Control Farmer’s Lung Farmers [nasdonline.org]

• Night Sweats

  Symptoms of chronic Farmer’s Lung include the same problems with the addition of night sweats, fatigue, decreased appetite and weight loss. Some people are immune to the condition, but there is no way of knowing who is likely to be affected. [thatsfarming.com]

• Headache

  Symptoms develop about 6 hours after exposure to dust containing fungal spores and include shortness of breath, headache, fever, and muscle aches. In acute attacks, the symptoms last for about a day. [meddict.org]

  Acute Stage: After four to eight hours symptoms such as headache, irritating cough, and shortness of breath upon physical exertion, appear. Subacute Stage: Symptoms persist without further exposure, and increase in severity. [en.wikipedia.org]

  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. [mouldfacts.ca]

  These symptoms include : Fever Chills Tight chest Difficulty breathing Cough (non-productive) Wheezing (sometimes) Headache Malaise Symptoms resolve spontaneously provided that exposure to the antigen is eliminated. [healthhype.com]

The diagnosis of farmer's lung can be made only if adequate clinical suspicion is raised, which should be based on information obtained from a detailed patient history and thorough physical examination. During history taking, the physician must gather data about the patient's occupancy, in order to assess potential exposure to thermophilic pathogens [1]. The physical examination may further aid in making a presumptive diagnosis by detecting dry crackles when auscultating the lungs [1]. After a careful assessment of signs and symptoms, imaging studies should be ordered. Plain radiography is usually the first radiograph employed, showing diffuse infiltrates in a ground glass pattern and patchy opacities, but high-resolution computed tomography (HRCT) is the gold standard for evaluation of the lung parenchyma in patients suffering from hypersensitivity pneumonitis [1] [5]. In addition to imaging studies, laboratory testing for precipitating immunoglobulin (Ig) G antibodies, skin prick testing, bronchial challenge testing using appropriate antigens, and spirometry are constitutive features of the workup [1] [3] [5]. Some authors advocate that a transbronchial biopsy (TBB) with subsequent histopathological examination should be obtained in order to solidify the diagnosis [1].

• Pulmonary Infiltrate

  FARMER'S lung resembles Loeffler's syndrome, for, at times, it manifests the triad of pulmonary infiltrations, eosinophilia and a benign clinical course. [nejm.org]

• Lymphocytosis

  There were no correlations between changes seen in individual pulmonary function and BAL lymphocytosis. [ncbi.nlm.nih.gov]

  In fact, a BAL lymphocytic count of less than 30% makes the diagnosis unlikely, except in smokers and more chronic forms in which lymphocytosis is less prominent. [slideshare.net]

• Thermoactinomyces Vulgaris

  vulgaris ICD-9-CM Volume 2 Index entries containing back-references to 495.0 : [icd9data.com]

  vulgaris, in addition to spirometry, pulmonary diffusing capacity (DL(CO)), and the evaluation of chronic bronchitis. [ncbi.nlm.nih.gov]

• Saccharopolyspora Rectivirgula

  The use of salt did not significantly decrease the amount of Saccharopolyspora rectivirgula, the actinomycetes most commonly involved in farmer's lung disease, or that of Absidia corymbifera, Eurotium amstelodami and Wallemia sebi, three moulds responsible [ncbi.nlm.nih.gov]

  Use(s): Detection of antibodies to Saccharopolyspora rectivirgula (previously known as Micropolyspora faenii ) to diagnose Farmers’ Lung. Description: Determination of the presence of antibodies to Saccharopolyspora rectivirgula. [pathology.leedsth.nhs.uk]

• Thermoactinomyces Sacchari

  This may include exposure to Saccharopolyspora rectivirgula, Thermoactinomyces vulgaris, Thermoactinomyces viridis, or Thermoactinomyces sacchari. These species are usually found in decaying organic matter, such as compost, hay or sugar cane. [news-medical.net]

  Thermophilic actinomycetes include a range of bacteria including Saccharopolyspora rectivirgula (formerly Micropolyspora faeni ), Thermoactinomyces vulgaris, Thermoactinomyces viridis, and Thermoactinomyces sacchari. [biotechlab.com.au]

  The thermophilic actinomycetes, apart from the Aspergillus species, which are the main causative factors includes Saccharopolyspora rectivirgula, Thermoactinomyces vulgaris, Thermoactinomyces viridis and Thermoactinomyces sacchari. [healthhype.com]

• Penicillium

  Our environmental and immunologic studies indicate Penicillium brevicompactum and P olivicolor as probable new antigens of FL in a cool and dry climate. [ncbi.nlm.nih.gov]

  Thermoactinomyces species (T. sacchari, T. vulgaris, T. viridis) and Saccharopolyspora rectivirgula are notable bacterial pathogens, whereas several fungal species (Aspergillus and Penicillium) have been linked to farmer's lung as well. [symptoma.com]

  Probable new antigens, Penicillium brevicompactum and P olivicolor. Chest. 1997 Jan. 111(1):245-8. [Medline]. Imai K, Ashitani J, Imazu Y, et al. [Farmer's lung cases of a farmer and his son with high BAL fluid beta-D glucan levels]. [emedicine.medscape.com]

• Decreased Lung Compliance

  [7, 8] If the acute exposure is large, a dramatic increase in inflammation leads to increased vascular permeability, which can alter the alveolar capillary units, thus promoting hypoxemia and decreased lung compliance. [emedicine.com]

Twenty patients were given prednisolone treatment for 8 wk. Sixteen patients received an 8-wk placebo treatment. One patient was withdrawn from the analysis when she terminated corticosteroid treatment because of side effects. [ncbi.nlm.nih.gov]

What Are The Treatments For Farmer's Lung? The gold standard for treatment for Farmer' Lung is to stay away from moldy hay. [epainassist.com]

We compared the clinical findings and the prognosis between 12 smokers (SM-FLD) and 31 non-smokers with FLD (NS-FLD). [ncbi.nlm.nih.gov]

[…] dust from feathers and faeces mushroom worker's lung is an allergic response to thermophilic actinomycetes spores in mould maltworker's lung - Aspergillus clavatus spores Links: pathology aetiology clinical features investigations diagnosis management prognosis [gpnotebook.co.uk]

Also Read: Byssinosis or Brown Lung Disease or Monday Fever: Causes, Signs, Symptoms, Diagnosis, Treatment, Prognosis Pneumoconiosis or Black Lung Disease: Symptoms, Diagnosis, Treatment, Prevention, Who is at Risk Bird Fancier's Lung: Causes, Symptoms [epainassist.com]

In the absence of the primary recognized FLD agent, Saccharopolyspora rectivirgula, its etiology remains unknown. A prospective case-control study was performed to find the etiology of FLD in this area. [ncbi.nlm.nih.gov]

Sheer speculations about the cause of these syndromes have given way to specific disease causes and genetic mapping of the etiologic agents of Farmer’s Lung. [oatext.com]

The epidemiological features of farmer's lung are analyzed and discussed and certain preventive measures are suggested. [ncbi.nlm.nih.gov]

This is in accordance with both the pathophysiological behaviour of the inhaled particulate antigen and the subsequent distribution of pulmonary changes in chronic farmer's lung. [ncbi.nlm.nih.gov]

Extrinsic Allergic Alveolitis - Pathology mini tutorial Pathophysiology Extrinsic allergic alveolitis is caused by inhalation of antigens that cause a hypersensitivity reaction in the respiratory system. [news-medical.net]

•Introduction •Definition •Aetiology •Pathophysiology •Clinical picture •Smoking •Investigations •Diagnostic criteria •Differential diagnosis •Treatment •Prognosis 3. Introduction 4. [slideshare.net]

Clearly, the risks of ignoring these preventive measures are not worth taking. [nasdonline.org]

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. [ncbi.nlm.nih.gov]

Diagnosis, Treatment, Prevention Chronic Obstructive Lung Disease or Chronic Obstructive Airway Disease Occupational Lung Disease: Causes, Symptoms, Treatment, Prevention Anatomy of Lungs & its Functions, Role of Lungs in Respirations & Talking, Tips [epainassist.com]

1. Cano-Jiménez E, Acuña A, Botana MI, et al. Farmer's Lung Disease. A Review. Arch Bronconeumol. 2016;52(6):321-328.
2. Selman M, Pardo A, King TE. Hypersensitivity pneumonitis: insights in diagnosis and pathobiology. Am J Respir Crit Care Med. 2012;15:314–324.
3. Bourke SJ, Dalphin JC, Boyd G, McSharry C, Baldwin CI, Calvert JE. Hypersensitivity pneumonitis: current concepts. Eur Respir J Suppl. 2001;32:81s–92s
4. Spagnolo P, Rossi G, Cavazza A, et al. Hypersensitivity Pneumonitis: A Comprehensive Review. J Investig Allergol Clin Immunol. 2015;25(4):237-250.
5. Lacasse Y, Cormier Y. Hypersensitivity pneumonitis. Orphanet J Rare Dis. 2006;1:25.
6. Malinen AP, Erkinjuntti-Pekkanen RA, Partanen PLK, Rytkönen HT, Vanninen RL. Long-term sequelae of farmer’s lung disease in HRCT: a 14-year followup study of 88 patients and 83 matched control farmers. Eur Radiol. 2003;13: 2212–21.