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Aspergillosis (Aspergillus)

Q: What is 'ragpicker's disease'?

It is an occupational form of aspergillosis occurring in individuals who regularly handle and inhale dust from old moldy paper, rags, or organic waste.

Q: Which specific species causes severe invasive pulmonary infections?

The most dangerous forms of invasive pulmonary aspergillosis, accompanied by vascular thrombosis, are caused by Aspergillus fumigatus.

Q: What is the danger of aflatoxins?

Species A. flavus and A. parasiticus secrete potent toxins that accumulate in food products. Their ingestion leads to alimentary poisonings capable of provoking liver cirrhosis and exerting carcinogenic effects.

Aspergillus spp.

For medical students2 min readUpdated 2026-10-10

Aspergillosis is an infectious disease caused by mold fungi of the genus Aspergillus. It most commonly affects the respiratory system in immunocompromised hosts and can manifest as an allergic reaction or a severe invasive form.

StructureSeptate hyphae with characteristic 'watering pot' conidiophores

Route of transmissionPrimary — airborne (inhalation of conidia with dust)

Dangerous toxinAflatoxin, capable of causing liver cirrhosis and cancer

ResistanceSpecies A. terreus is resistant to amphotericin B

Morphology and Cultural Characteristics

Pathogens of aspergillosis are septate mold fungi. They possess branching mycelium and reproduce asexually by forming spores called conidia.

Microscopic structure: The spore-bearing hypha ends in a characteristic swelling (the conidiophore), upon which sterigmata (phialides, metulae) are arranged in one or two rows. Chains of conidia extend from them. Under the microscope, this complex structure strongly resembles a watering can.
Pigmentation: Colony color directly depends on the color of the formed conidia. They can be black, green, white, or yellow.
Cultivation: Aspergilli are obligate aerobes. They grow exceptionally well on standard nutrient media (wort agar, Czapek-Dox agar, Sabouraud agar) with an optimal temperature of 24–37 °C. Initially, fluffy white colonies grow, which acquire a species-specific color within 2–4 days.

Epidemiology and Pathogenicity Factors

Fungi of the genus Aspergillus are ubiquitous: their conidia are constantly present in soil, water, ambient air, and decaying plant matter. Out of approximately 200 known species, about 20 are considered pathogenic to humans, with A. fumigatus, A. niger, A. flavus, A. terreus, and A. nidulans playing the leading roles.

The primary route of infection is airborne (inhalation of conidia). Contact transmission is less common. Risk groups include individuals in specific occupations (working with dust or moldy paper — the so-called 'ragpicker's disease'). Iatrogenic factors are of paramount importance, including invasive medical procedures such as bronchoscopy, punctures, or vascular catheterization.

Key pathogenicity factors of Aspergillus:

Aggressive enzymes: the pathogen synthesizes protease, elastase, collagenase, and acid phosphatase, which destroy host tissues.
Toxins: certain species (especially A. flavus and A. parasiticus) produce potent aflatoxins. When these accumulate in food products, alimentary aflatoxicoses develop, characterized by pronounced carcinogenic effects and the potential to cause severe liver cirrhosis.

Pathogenesis and Clinical Forms

The development of severe forms of aspergillosis is closely linked to immunodeficiency. Normally, cellular defense factors (macrophages and granulocytes simply phagocytose and digest them) successfully handle fungal conidia, and the patient develops delayed-type hypersensitivity (DTH). However, when the immune system fails, the pathogen can disseminate, affecting the central nervous system, endocardium, and paranasal sinuses.

Main clinical variants:

Invasive pulmonary aspergillosis. The most severe form, most commonly caused by A. fumigatus. It is characterized by rapid invasive fungal growth, invasion into blood vessels, and subsequent thrombosis.
Allergic bronchopulmonary aspergillosis (ABPA). The disease mimics bronchial asthma. It is characterized by allergic alveolitis and persistent blood eosinophilia.
Aspergilloma (aspergillus mycetoma). A specific form of granuloma, most commonly localized in lung tissue. It represents a dense ball of mycelium surrounded by a thick fibrous wall.
Cutaneous aspergillosis. Develops either from direct contamination of an open wound by spores or via hematogenous dissemination. Hyperemic plaques appear on the skin and subsequently ulcerate.

Diagnosis, Treatment, and Prevention

The fundamental and primary method of laboratory diagnosis is microscopy. Smears of pus, sputum, or affected tissues (using Gram staining) are examined for septate mycelium and characteristic conidial chains. Wet mounts using 10% KOH are widely used. Additionally, culture isolation of a pure strain, serological tests (ELISA, precipitation reactions), and skin-allergy tests are employed.

Treatment: Based on the administration of antifungals (amphotericin B, itraconazole, caspofungin). Crucially, the species A. terreus exhibits intrinsic resistance to amphotericin B! For localized forms (e.g., aspergilloma), surgical excision of affected tissue areas is often necessary.
Prevention: Relies on strict sanitary and hygienic measures. To prevent nosocomial (iatrogenic) infection, absolute sterility control of medical equipment and maximum indoor air purity are required.

Mnemonic

Remember the characteristic appearance of the Aspergillus conidiophore under the microscope by associating it with a garden watering can: a swollen spore-bearing hypha with rows of sterigmata from which chains of conidia extend like streams of water.

Frequently asked questions

Which specific Aspergillus antigens are detected in blood and bronchoalveolar lavage fluid using ELISA?

The specific Aspergillus antigen detected in blood and bronchoalveolar lavage (BAL) fluid is galactomannan. Its detection is officially included in the diagnostic criteria for invasive aspergillosis. Testing for galactomannan in BAL has high sensitivity and specificity (> 80%) and is considered more effective than serum analysis. Optical density index thresholds are used for confirmation: a positive result is defined as ≥ 0.5 in blood and ≥ 1.0 in BAL fluid.

Which immunoglobulin classes are measured in the serological diagnosis of aspergillosis?

Immunoglobulin classes E (IgE) and G (IgG) are measured during the serological diagnosis of aspergillosis.

Laboratory evaluations include:

Total IgE — used for screening and monitoring allergic bronchopulmonary aspergillosis (ABPA); elevation serves as an early sign of exacerbation.
Specific IgE (Aspergillus fumigatus) — detected during the onset or exacerbation of ABPA.
Specific IgG (Aspergillus fumigatus) — measured when ABPA or chronic pulmonary aspergillosis (CPA) is suspected.

Isolated elevation of specific IgG in the absence of clinical and radiological criteria does not confirm infection.

What specific conditions and diseases are the major risk factors for developing invasive aspergillosis?

Risk factors for invasive aspergillosis include conditions associated with immunodeficiency.

Confirmed risk factors include:

prolonged neutropenia lasting 10 days or more;
severe neutropenia with a granulocyte count < 0.5 × 10⁹/L;
administration of glucocorticoids;
therapy with fludarabine or alemtuzumab;
post-lung transplant status on immunosuppressive therapy.
Invasive aspergillosis occurs almost exclusively in immunocompromised individuals, particularly patients with severe neutropenia.

What is 'ragpicker's disease'?