Mesophilic · Extended-panel species

Aspergillus parasiticus

Soil and grain-associated Aspergillus that produces the full aflatoxin set (B1, B2, G1, G2). Closely related to A. flavus and offered by several labs as an extended-panel add-on.

Extended panelMesophilic · Aw ≥ 0.80

Moisture niche · where this species can grow

XerophilicAw < 0.80
MesophilicAw 0.80–0.89
HydrophilicAw ≥ 0.90
Min Aw 0.80
← Drier conditions toleratedRequires liquid water →
Minimum Aw
0.80
EPA reference (GM)
< 0.4 SE/mgMeklin AHHS threshold
Mycotoxin profile
4+ documented
Ecological role
Secondary colonizer

The < 0.4 SE/mg reference value is Meklin 2004's AHHS exclusion threshold: the paper retained species whose geometric mean was at least 2 spores per 5 mg dust (≈ 0.4 spores/mg) and eliminated the rest. This species was measured across the 1,096-home AHHS sample and characterized below that threshold, used here as a conservative ceiling on its true GM, not a percentile band. A detected value of X SE/mg implies an elevation factor of at least X ÷ 0.4 over the EPA reference, a lower bound, since the true GM is below 0.4. See the 82-species story for the math.

About Aspergillus parasiticus

Aspergillus parasiticus is a toxigenic mold of the Aspergillus section Flavi, closely related to and often co-occurring with A. flavus. The species is distinctive among indoor-relevant Aspergilli for producing the complete aflatoxin set (B1, B2, G1, and G2), whereas A. flavus produces only the B-series. It is offered as an add-on by several commercial dust testing labs because the G-series aflatoxin route is otherwise unmeasured on the standard 36-species ERMI panel.

Taxonomy

Ascomycota → Eurotiomycetes → Eurotiales → Aspergillaceae → Aspergillus section Flavi

Ecology and habitat

A. parasiticus is a soil and grain-associated species with a warm-climate distribution that has expanded into temperate regions over the past several decades. It is one of the principal causes of preharvest aflatoxin contamination in peanuts, maize, cottonseed, and tree nuts globally[5][6]. The species shares ecological niches with A. flavus; the two are often co-isolated from the same fields and substrates.

Indoor relevance

Indoors, A. parasiticus is less commonly detected than A. flavus but when it is found in dust it is more often associated with stored foods (peanuts, tree nuts, grains) or with warm, humid places where starchy materials are present. The species's principal indoor-relevance point is its G-series aflatoxin production: because A. flavus produces only B1 and B2, panels that distinguish A. parasiticus from A. flavus are the only commercially available route for detecting a G-series-producing organism via the ERMI dust-DNA methodology.

Cardinal physiology

Minimum water activity for growth: Aw 0.80 (García et al. 2011)[2]. Optimum growth occurs at Aw 0.95–0.99 with temperatures around 35 °C; the species tolerates 17–42 °C. Aflatoxin production has a higher water requirement than growth itself. Production requires Aw ≥ 0.85, with peak yields at 0.90–0.95. Production is temperature-optimal at ~28–35 °C, with B1 often peaking near 35–37 °C and G1 production favored at slightly lower temperatures (20–30 °C)[3][4]. This distinction matters indoors: substrate-DNA detection of the organism does not establish that aflatoxin biosynthesis was active at the detection site, only that the organism was present.

Aflatoxin production requires Aw ≥ 0.85; optimum 0.90–0.95. Temperature optima differ between aflatoxin variants: B1 peaks at 35–37 °C, G1 at 20–30 °C.

Secondary metabolites

A. parasiticus produces the full aflatoxin biosynthetic family (B1, B2, G1, G2) along with kojic acid, aspergillic acid, and parasiticol (a furochromanone aflatoxin precursor). Notably, unlike its sister species A. flavus, A. parasiticus does not produce cyclopiazonic acid. This is one of the chemotaxonomic features distinguishing the two species. Aflatoxin B1 is the most potent natural carcinogen characterized and is classified by IARC as a Group 1 carcinogen on the basis of dietary exposure data. The chemistry, mechanism, and regulatory references for aflatoxins are covered on the linked mycotoxin page.

Compounds documented as produced by Aspergillus parasiticus (presence and quantity vary by chemotype, strain, and substrate):

Aflatoxins B1, B2, G1, G2 (full B + G series)Kojic acidAspergillic acidParasiticol (furochromanone aflatoxin precursor)

DNA-based detection of a mycotoxin-producing species in household dust does not directly establish exposure to that mycotoxin at any specific concentration.

Lab availability

Some commercial dust testing labs offer this species as an extended-panel option. Specific lab coverage changes over time: check with your laboratory for current panel options.

Related

Aflatoxins (B1, B2, G1, G2)Mycotoxin reference page for the family this species produces in full.Aspergillus flavusClosest relative on the EPA 36 panel; produces aflatoxins B1 and B2 only.Beyond the 36Why ERMI doesn't include this species and which labs add it.

References

  1. Meklin T, Haugland RA, Reponen T, Varma M, Lummus Z, Bernstein D, Wymer LJ, Vesper SJ. Quantitative PCR analysis of house dust can reveal abnormal mold conditions. J Environ Monit. 2004;6(7):615–620.
  2. García D, Ramos AJ, Sanchis V, Marín S. Modelling mould growth under suboptimal environmental conditions and inoculum size. Int J Food Microbiol. 2011;147(1):72–79.
  3. Schmidt-Heydt M, Rüfer CE, Abdel-Hadi A, Magan N, Geisen R. The production of aflatoxin B1 or G1 by Aspergillus parasiticus at various combinations of temperature and water activity. Mycotoxin Res. 2010;26:241–246.
  4. Pitt JI, Hocking AD. Fungi and Food Spoilage. 3rd ed. New York: Springer; 2009.
  5. International Agency for Research on Cancer. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol. 82: Some Traditional Herbal Medicines, Some Mycotoxins, Naphthalene and Styrene. Lyon: IARC; 2002.
  6. Council for Agricultural Science and Technology. Mycotoxins: Risks in Plant, Animal, and Human Systems. Task Force Report 139. Ames, IA: CAST; 2003.