ORGANIC DUSTS - Page 3 of 6

Module 4: Organic Dusts - Lecture (Continued)

ORGANIC DUST TOXIC SYNDROME:

Occurs when organic dusts/aerosols containing large quantities of micro-organisms are inhaled.
Clinical features: fever, myalgia, chest tightness, cough, headache and dyspnoea 3-8 hours after exposure; no prior exposure required; no serum antibodies detected; spontaneous recovery within 24 hours after withdrawal from exposure.
Mechanisms unclear but thought to be due to endotoxin (not immunological) activating complement cascade and cytokine release.
Exposure contexts: cotton, swine confinement buildings, grain silos.
Treatment remove from exposure and supportive: no antibiotics/steroids indicated.

**Table 5. Causes of Hypersensitivity Pneumonitis (HP)**
Antigen	Exposure	Syndrome
Bacteria Thermophilic bacteria: Micropolyspora foeni Thermoactinomycetes vulgaris T. sacchari T. candidus Nonthermophilic bacteria: Bacillus subtilis B. cereus	"Moldy" hay "Moldy" sugarcane Mushroom compost Heated water reservoirs Water Detergent	Farmer's lung Bagassosis Mushroom worker' lung Humidifier lung Humidifier lung Washing powder lung
Fungi Aspergillus sp. Aspergillus clavatus Penicillium casei P. roquefortii Alternaria sp. Cryptostroma corticale Graphium Aurebasidium pullans Merulius lachrimans Penicillium frequentans Aureobasidium pullulans Cladosporium sp. Thichosporon cutaneum	"Moldy" hay Water Barley Cheese Wood pulp Wood bark Wood dust Rotten wood Cork dust Water Hot tub mists Damp wood and mats	Farmer's lung Ventilator pneumonitis Malt worker's lung Cheese washer's lung Wood pulp worker's lung Maple bark stripper's lung Sequoiosis Dry rot lung Suberosis Humidifier lung Hot tub HP Japanese summer-type HP
Amoebae Naegleria gruberi Acanthamobea polyphaga A. castellani	Contaminated water	Humidifier lung
Animal proteins Avian proteins Urine, serum, pelts Wheat weevil (Sitophilus granarius)	Bird droppings, feathers Rats, gerbils Infested flour	Bird breeder's lung Animal handler's lung Wheat weevil lung

Immunologically mediated lung disease affecting the lung parenchyma.
Commonly caused by organic materials especially spores of thermophilic. bacteria eg. thermoactinomycetes (moldy vegetable compost, air humidification systems) and saprophytic fungi, for example, Alternaria (wood pulp) as well certain proteins (urine, feces) of birds and animals (see Table 5 for a more detailed list)
Particle size < 5 µm reach lower respiratory tract and cause inflammation of the alveoli and small bronchioles (see figure on the right).
Immunological mechanism: immune complex and cell mediated response to repeated exposure and sensitization to an inhaled antigen.
Clinical presentation dependent on immunologic response of host; intensity; frequency of exposure.
Two clinical entities: acute and chronic form:

Acute form:
- 4-6 hours after exposure respiratory and systemic symptoms (chills, fever, cough, dyspnoea, malaise, myalgia) occur; resolves in 12-18 hours;
- bi-basal crepitations on chest examination;
- chest x-ray: fine reticulonodular pattern or soft patchy infiltrates; clears in 1-2 weeks (Picture on the left, above);
- lung function tests: restrictive picture;
- eosinophilia (10%);
- diffuse lymphocytic infiltrate with sarcoid-like granulomas on biopsy (Picture on the right, above)

chronic exposure results in chronic disease with irreversible damage without acute flu-like episodes
symptoms of chronic progressive dyspnoea, non-productive cough, malaise, weakness, weight loss, occasional clubbing of fingers
CXR, LFT and biopsy findings are consistent with pulmonary fibrosis (Picture on the left above) or rarely with COAD
Diagnosis: Is made on history; CXR infiltrates (irregular opacities); presence of serum precipitins (IgG) (Picture on the right above); inhalation challenge tests; and biopsy.
NOTE: A number of cases are negative for precipitins and up to 50% of symptomatic exposed individuals may be positive.
Treatment: remove from exposure; steroids useful in severe cases.

Postgraduate Diploma in Occupational Health (DOH) - Modules 3 – 5: Occupational Medicine & Toxicology by Prof Rodney Ehrlich & Prof Mohamed Jeebhay is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
Permissions beyond the scope of this license may be available at http://www.healthedu.uct.ac.za/