Page 1052 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

984 SECTION | XV Mycotoxins

VetBooks.ir TABLE 69.1 Species of Aspergillus Identified as Producers of Aflatoxins (AFs) Mycotoxins Identified b

a
Species
Country
A. bombycis (F) Japan, Indonesia AFB, AFG, KA
A. flavus (F) Ubiquitous AFB 1 , AFB 2 , KA, CPA, others
A. nomius (F) United States, Thailand, S. America AFB, AFG, KA, others
A. parasiticus (F) Likely ubiquitous AFB, AFG, KA, others
A. parvisclerotigenus (F) Africa AFB, AFG, CPA, KA
A. pseudocaelatus (F) Argentina AFB, AFG, CPA, KA
A. minisclerotigenes (F) United States, Africa, Australia, S. America AFB, AFG, KA, CPA, other
A. arachidicola (F) S. America AFB, AFG, KA, CPA, others
A. pseudonomius (F) United States AFB1, KA, other
A. pseudotamarii (F) Japan, S. America AFB 1 , KA CPA
A. ochraceoroseus (O) Africa AFB 1 , AFB 2 , ST, others
A. rambellii (O) Africa AFB 1 , AFB 2 , ST, others
E. astellata (N) S. America AFB 1 , ST, others
E. olivicola (N) S. Europe AFB 1 , ST, others
E. venezuelensis (N) S. America AFB 1 , ST, others
a
Section and F, Flavi; O, Ochraceorosei; and N, Nidulantes.
b
AFB, aflatoxin B; AFG, aflatoxin G; CPA, cyclopiazonic acid; ST, sterigmatocystin; KA, kojic acid (not mycotoxins). For others see Varga et al. (2009,
2011).
Source: Adapted with permission from Varga, J., Frisvad, J.C., Samson, R.A., 2009. A reappraisal of fungi producing aflatoxins. World Mycotoxin. J. 2,
263 277.

to plant residues, spores, mycelia, or sclerotia of aflatoxi- growth conditions for aflatoxigenic species are described
genic fungi are commonly found in soil, commodity stor- as requiring moisture contents in equilibrium with

age areas, processing facilities, and in the distribution 80% 85% or more and temperatures of 13 42 C with

systems for manufactured products. Strains of A. flavus optimum growth at 25 37 C. For example, the critical
can vary in AF capability from nontoxic to highly toxi- moisture content for growth of A. flavus in starchy cereal
grains is 17% 18%, soybeans 17% 17.5% and for pea-
genic and are more likely to produce more aflatoxin B 1
(AFB 1 ) than aflatoxin G 1 (AFG 1 ). A. flavus and other spe- nuts is 9% 10.5%. The upper limit of moisture for
cies can also produce cyclopiazonic acid. Strains of growth of A. flavus and production of AFs is about 30%.

A. parasiticus generally have less variation in toxigenicity A. flavus will grow slowly below 13 C, and most rapidly
and generally produce AFB 1 and varying amounts of at 37 C, but does not produce AFs at temperatures below

AFB 2 , AFG 1 , and AFG 2 . The AF profile produced by 13 C or above 42 C. In addition to temperature and equi-

A. nomius is like A. parasiticus, and like A. parasiticus,is librium relative humidity, other factors that influence AF
not known to produce cyclopiazonic acid. Aflatoxigenic production are carbon, nitrogen, plant metabolites, and
strains of Aspergillus can also produce sterigmatocystin sugars in substrates. High maximum and high minimum
(Table 69.1). temperatures with high net evaporation are more impor-
tant triggers than temperature and humidity alone. High
AF production generally occurs when the fungus grows in
CONDITIONS FOR AFLATOXIN the seed embryo. Both epigenetic and genetic factors
affect AF production and the interactions are not well
PRODUCTION
understood. Aflatoxigenic A. flavus isolates vary from
The fungi associated with AF production are A. flavus, 40% to .70% of the total A. flavus population. The per-
A. parasiticus, and A. nomius, and these fungi are com- cent of aflatoxigenic isolates can vary between ingredients
mon in most soils and are usually involved in decay of and finished feeds, and finished feeds that have spoiled
plant materials (Jacobsen et al., 2007). The general can have high primary production of AFs. Seeds damaged