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VetBooks.ir Chapter 69

Aflatoxins

Robert W. Coppock, Ralph G. Christian and Barry J. Jacobsen

INTRODUCTION health concern is that plant-source illicit drugs may
contain AFs, and the interactions between AFs and infec-
Aflatoxins (AFs), on a worldwide scale, are considered
tious diseases can contribute to spread of infectious
the most important mycotoxins in human foods and ani-
diseases in populations consuming these drugs.
mal feedstuffs because of their hepatotoxicity and carci-
Most governmental jurisdictions regulate the levels of
nogenicity. In the late 1950s and early 1960s, AFs were
AFs allowed in animal feedstuffs and human foods
identified as the cause of the mysterious turkey “X” dis-
because of their toxicity. The allowable levels of AFs in
ease in Great Britain (Allcroft and Lewis, 1963). In the
animal feedstuffs and human foods vary with governmen-
U.S., studies incriminated AFs as the cause of epizootic
tal jurisdictions and the perceived risk. For example, the
hepatitis in dogs, as the cause of moldy corn poisoning in
regulated level for AFs in feedstuffs for dairy animals is
pigs and as a potent carcinogen in rainbow trout
lower than AFs in feedstuffs fed to beef cattle because of
(Newberne et al., 1966a, b; Newberne and Butler, 1969).
AFs being excreted in milk for human consumption.
AF linkages to human liver disease were made in the
Commodities considered unsafe for human foodstuffs are
1960s. Since these early discoveries, intensive research
often incorporated into animal feedstuffs, and most gov-
has shown and continues to show that the risk of exposure
ernments have regulations allowing this diversion. Grain
to AFs is a worldwide animal and human health issue.
and other seeds used for feeding wildlife can be high in
Many authors believe other fungal metabolites produced
AFs and these feedstuffs are generally under-regulated.
by aflatoxigenic and other fungi contribute to the toxicol-
Regulatory information for AFs is generally posted on
ogy observed under field exposure conditions (Coppock
government and WHO websites.
and Jacobsen, 2009).
AF-linked adverse health effects occur in companion
animals, livestock, poultry, aquatic animals, humans, and AFLATOXIGENIC FUNGI
other species because AFs are potent hepatotoxins, muta-
gens, carcinogens immunosuppressants, teratogens, have Varga et al. (2009) have reviewed aflatoxigenic species.
adverse epigenetic effects, and are linked with reproduc- Three sections likely account for all the aflatoxigenic spe-
tive dysfunctions, and stunted growth (Allcroft and Lewis, cies of Aspergillus, namely Flavi, Ochraceorosei, and
1963; Eaton and Gallagher, 1994; Shuaib et al., 2010a). Nidulantes (Table 69.1). The most commonly recognized
AFs are the most potent naturally occurring hepatic carci- aflatoxigenic fungi are Aspergillus flavus, Aspergillus
nogens. AF contamination causes economic losses of corn, parasiticus, and Aspergillus nomius; other species of
cottonseed, peanuts, sorghum, wheat, rice, nuts and spices, Aspergillus have been reported to produce AFs and are
condiments, other commodities and processed foods. given in Table 69.1. Aflatoxigenic species of Aspergillus
Because of their prevalence and toxicity, AFs are impor- commonly grow in plant-source debris on the soil and can
tant worldwide in public health, with concerns centered on also grow in feedlot manure. Insects and wind currents
both primary poisoning from AFs in commodities, food, spread the spores of aflatoxigenic fungi to plants and
and feedstuffs, and relay poisoning from AFs in milk and these fungi commonly colonize floral organs and areas of
other animal products. Aflatoxicosis in the human popula- insect damage. Management of insect pests in the order
tion, especially in areas stricken by poverty, drought, and Lepidoptera is a key to reducing AF contamination in
other adverse growing conditions for plants, is an impor- corn, cotton and some tree nuts. In corn, infection can
tant public health problem and may be worsening by take place via silks and the subterranean flowers of pea-
increasing climate stressors on plants. Another public nuts can also be infected without insect injury. In addition

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