4 Department of Respiratory Medicine, Belfast City Hospital, Belfast BT9 7AD
5 Department of Respiratory Medicine, The Queen's University of Belfast, School of Medicine, Royal Victoria Hospital, Grosvenor Road, Belfast.
Mushroom worker's lung [MWL], (also known as mushroom compost worker's lung, compost lung, mushroom lung and mushroom picker's lung) is an allergic respiratory disease, associated with occupational exposure to a variety of substances in the mushroom and compost industries.
This disease shares several characteristics with a variety of other occupational respiratory diseases, where over 300 allergens have been described, including:
Malt worker's lung,
Maple bark stripper's lung,
Peat moss worker's lung,
Wood pulp worker's lung and
Wood trimmers lung.
Medically, MWL is known as hypersensitivity pneumonitis, (HP), or extrinsic allergic alveolitis, which was first described in Iceland in 1874.
MWL is an immune-mediated interstitial lung disease caused by the presence of several foreign environmental antigens, including mushroom spores and mould spores.
Historically, the mushroom industry has been associated with a high incidence of HP, resulting in an HP-associated condition known as Mushroom Worker's Lung (MWL).
MWL presents clinically in sensitized patients with a variety of signs and symptoms, including
sudden onset of fever,
shortness of breath and
rapid breathing (in the acute form of the disease),
with increasing symptoms including:
developing a productive cough,
weight loss (in the subacute or intermittent form of the disease);
finally leading to the most severe symptoms of the chronic disease,
including respiratory distress,
often accompanied by muscle wasting,
weight loss and
clubbing of the fingers and toes.
Traditionally MWL has been associated with exposure to environmental fungi and bacteria, which are found in huge numbers in composting operations and mushroom growing houses.
Table 1 (below) describes several bacteria and fungi which have been associated with this disease state. Furthermore these organisms do not constitute a public health risk to members of the general population and the clinical significance of these organisms lies solely with sensitized individuals with MWL.
Range of microbiological and (more recently) mushroom antigens associated with the development of Mushroom Workers' lung in affected patients
More recently, the presence of mushroom spores themselves may constitute a further risk, in addition to that posed by environmental fungi and bacteria, leading to the development of MWL in sensitized patients.
Hypersensitivity pneumonitis remains an important industrial disease in mushroom workers. It has a significant morbidity and early diagnosis and removal from exposure to the antigen is critically important in its management.
Recently, several new allergens have been described, particularly those from mushroom species originating in the Far East, which are of clinical significance to workers occupationally exposed to such allergens in the cultivation, picking and packing of commercial mushroom crops.
Importing of exotic mushrooms including Shiitake are common in EU countries and some of the exotic species of mushrooms are cultivated for local markets. This practice may contribute to an increase in clinical cases of MWL
Over this past few years, our research group has been active in developing new laboratory tests for better detection of agents of MWL .
In a recently published scientific / medical review by our respiratory research group , we describe the clinical presentation of MWL associated with mushroom spores from a variety of species, as detailed in Table 1.
For example, a young man developed severe asthma a few months after starting work in a factory producing a single type of mushroom, namely Pleurotus cornucopiae (a basidiomycete).
Immunological investigations, performed with material recovered from the filtering devices of the mushroom's bed, led to demonstration of specific IgE and IgG against spore extracts and to isolation of one discriminant antigen (molecular weight: 10.5 kd).
Most of the recently described cases of HP have been first reported in Asia, where commercial production of these cultivars has taken place.
Changing culinary trends have resulted in an increase in the diversity of fungi cultures commercially.
In addition it is anticipated that the commencement of cultivation of such cultivars locally in the UK will allow for the introduction of foreign fungal proteins to new and immunologically naive populations of local or migrant workers who carry out processing functions in the mushroom industry.
Such a transfer of culinary trends reinforces the effects of the Columbian Exchange Concept on the allergic response of Old and New World inhabitants as previously described .
Salvaggio argued that the interchange of many species of fauna, flora, fowl and fruits between the Old and New Worlds resulted in increased manifestations of allergic reactions to many of these new substances.
Likewise, we should be aware that the transfer of exotic mushroom production from Asia to Europe carries with it an increased risk of allergic reactions and MWL to new industrial worker populations and it remains to be seen whether the incidence of MWL in Europe will rise with the introduction of these new cultivars.
MWL is a significant occupational respiratory disease in the mushroom and compost industries, where the work environmental and host factors of the sensitized patient are responsible for the onset of the disease.
Very recently (May 2005), the first scientific publication  has been released demonstrating a genetic predisposition to Bunashimeji mushrooms (Hypsizigus marmoreus), with a certain human tissue type (HLA Class II) being more associated with no allergy and MWL. These workers however were unable to demonstrate similar findings with honshimeji mushrooms (Lyophyllum aggregatum,).
In order to minimise development ofMWL, the mushroom and compost industries should continue to develop in-house educational and awareness programmes, as well as pro-active surveillance / monitoring of workers by occupational health care professionals.
Any worker in these industries, who is exposed to any of the allergens as described above and who experiences unusual respiratory symptoms, should seek medical advice from their doctor immediately.
Xu J, Rao JR, Millar BC, Elborn JS, Evans J, Barr JG, Moore JE. Improved molecular identification of Thermoactinomyces spp. associated with mushroom worker's lung by 16S rDNA sequence typing. J Med Microbiol. 2002;51:1117-27.
Moore JE, Convery RP, Millar BC, Rao JR, Elborn JS. Hypersensitivity pneumonitis associated with mushroom worker's lung: an update on the clinical significance of the importation of exotic mushroom varieties. Int Arch Allergy Immunol. 2005;136:98-102.
Salvaggio JE. Fauna, flora, fowl, and fruit: effects of the Columbian Exchange on the allergic response of New and Old World inhabitants. Allergy Proc. 1992;13:335-44.
Suzuki K, Tanaka H, Sahara H, Tanaka N, Tamura Y, Naruse T, Inoko H, Tsushima K, Kubo K, Abe S, Sato N. HLA class II DPB1, DQA1, DQB1, and DRB1 genotypic associations with occupational allergic cough to Bunashimeji mushroom. Tissue Antigens. 2005;65:459-66
7/1/2010 6:00:57 PM awesome article,proved vry helpful for my project work! farha, india
9/6/2010 8:13:13 PM I've developed a lung infection which turned into a severe head cold. There was a large dump of mushroom manure near my house which sat unturned for around 4 days. The smell was very strong and after just 1 day of exposure, I became very ill. I am wondering about the safety of this type of product with surrounding homes and livestock. I have never been this sick. Susan, Santa Paula, CA
4/18/2015 11:03:28 PM I am living beside a compost manufacturing and worry about contracting chronic lung or other illness.i don't seem to be able the information on how spores survive in the heavy ,foul smelling envoirment I am forced to live in. Aine, Tyholland ireland
6/15/2017 11:27:14 AM I've been diagnosed with Pulmonary Fibrosis . 6 years now suspect allergy to Parrotts . Terminal . About the same time I developed symptoms I was using a lge amount of Compost in creating garden beds . Does any body think there is a connection ? Appreciate comments & opinions please . Evelyn Floyd, NSW. AUSTRALIA
10/18/2018 10:33:27 AM I got a large load of muchroom compost delivered and spread it all over the lawn with my hands. I got such a bad asthma attack the same night and now three days of short breath coughing, severe chest pains and cortisone we took xrays with no infection showing. The minute I opened my door this morning onto my muchroom compost lawn my asthma got so bad with chills. Could this be a reaction to the muchroom compost. Marguerite , South Africa
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