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Aflatoxin Fact Sheet

Synopsis of Aflatoxin

Aflatoxins are naturally occurring mycotoxins that are produced by many species of Aspergillus, a fungus. in common and widespread in nature and are most often found when crops are exposed to a high humidity environment over a long period of time or are damaged in stressful conditions such as drought, a condition which lowers the barrier to entry. The native habitat of Aspergillus is in soil, decaying vegetation, hay, and grains undergoing microbiological deterioration. favors hot and humid climate and most commonly affects crops, such as cereals (maize, sorghum, pearl millet, rice, wheat), oilseeds (peanut, soybean, sunflower, cotton), spices (chili peppers, black pepper, coriander, turmeric, ginger), and tree nuts (almond, pistachio, walnut, coconut). The toxins can invade the food supply at any time during production, processing, transport, and storage. They can also be found in the milk of animals which are fed contaminated feed. Aflatoxins are toxic and carcinogenic to animals, including humans. After entering the body, aflatoxins are metabolized by the liver to an intermediate reactive, aflatoxin M1, an epoxide. There are at least 13 different types of aflatoxin produced in nature, with aflatoxin B1 considered to be the most toxic.

  • Transmission:
    • Consumption of food contaminated with aflatoxins.
  • The relative frequency of aflatoxicosis in humans in the U.S. is unknown. No outbreaks have been reported in humans and only sporadic cases have been reported in animals.
  • Major types of Aflatoxins:
    • B1 (a potent carcinogen in humans and animals and the most toxic of its type)
    • B2
    • G1
    • G2
    • M1
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Clinical Signs and Symptoms
Animals:
  • Aflatoxins, especially B1, is carcinogenic and causes liver damage and cancer
  • Susceptibility varies with species and age
    • Young (pre-weaning to early adolescence) are more susceptible
    • Trout, ducks, turkey, poultry, and pre-weaning pigs are highly sensitive
    • All swine, growing turkeys, broiler chicks, pre-ruminant calves, dogs, and horses are moderately susceptible
    • Beef feedlot cattle, open cows, and sheep are most resistant
  • Aflatoxin generally does not interfere with fertility or cause abortions; however, newborn animals nursing dams that consume aflatoxins can be poisoned by the aflatoxin M1 metabolite that is excreted in milk
  • Click here for more information about aflatoxins and animal health (Osweiler, 2005)7
  • Follows the rules of dosage and response:
    • Small amounts cause mild or negligible effects (1 part per million in feeds)
      • Poor growth
      • Interfere with the immune system
      • May result in liver damage and bleeding
    • Larger amounts cause increasingly serious effects
      • Acute loss of appetite
      • Depression
      • Hemorrhage
      • Diarrhea
      • Death
    • Prolonged exposure
      • Slow growth
      • Reduced milk production
      • Hemorrhage
      • Jaundice
      • Suppression of immune system
      • Organ damage and/or cancer
Poultry:
  • Clinical signs and symptoms:
    • < 600 ppm
      • Reduced immune system function (possible)
      • Bruising
    • 1,000-2,500 ppm:
      • Decreased fat digestion
      • Fat in droppings
      • Decreased gain and feed efficiency
    • 5,000 to 10,000 ppm
      • liver necrosis
      • Hemorrhage
      • Death
Swine:
  • Clinical signs and symptoms:
    • < 200 to 500 ppm
      • Reduced growth and feed efficiency
      • Reduced immune system function (possible)
      • Reduced response to vaccines
    • 800 to 2,000 ppm:
      • Subacute and may be lethal
      • Hepatic necrosis
      • Jaundice
      • Liver fibrosis and hemorrhages
      • Slow growth
      • Poor appetite
    • 2,000 to 4,000 ppm
      • Lethal from multiple exposures
      • Liver damage
      • Jaundice
      • Slow growth precede death
    • 10,000 to 20,000 ppm
      • Single exposure can be lethal
      • Hemorrhage
      • Acute liver damage
Cattle:
  • Click here for more information of aflatoxicosis in livestock published by South Dakota State University.6
  • Clinical signs and symptoms:
    • 2,000 to 4,000 ppm
      • Reduced milk production
      • Rumen dysfunction
      • Off feed
      • Aflatoxin residues in milk
    • 10,000-20,000 ppm:
      • Icterus hemorrhage
      • Liver necrosis
      • Death in one to two weeks
Humans:
  • High levels aflatoxin exposure produces as acute necrosis, cirrhosis, and carcinoma of the liver exhibited by hemorrhage, acute liver damage, edema, alteration indigestion, and absorption and/or metabolism of nutrients.
  • No animal species is immune to the acute toxic effects, although humans do have an extraordinarily high tolerance for aflatoxin exposure and rarely succumb to acute aflatoxicosis
  • Chronic, subclinical exposure does not lead to as dramatic of symptoms as acute aflatoxicosis.
  • Children are particularly affected by aflatoxin exposure which leads to stunted growth and delayed development
  • Chronic exposure also leads to a high risk of developing liver cancer, as the metabolite, Aflatoxin M1, can intercalate into DNA and alkylate the bases through its epoxide moiety
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Diagnosis and Treatment
Diagnostic Samples:
  • Urine
  • Blood
  • Liver biopsies
Differential Diagnosis:
  • Differential diagnoses include the following:
    • Acetominophen toxicosis
    • Amanita mushroom intoxication
    • Idiosyncratic drug reaction
    • Cycas or Zamia plant ingestion
    • Acute/chronic copper intoxication
    • Blue-green algae intoxication
    • Iron intoxication
    • Carbon tetrachloride intoxication
    • White phosphorus intoxication
    • Phenol intoxication
Clinical Diagnosis:
  • Aflatoxicosis may be suspected when the patient exhibits the following characteristics:
    • Cause not readily identifiable
    • Condition not transmissible
    • Syndromes may be associated with certain batches of food
    • Treatment with antibiotics or other drugs have little effect
    • The case occurs when weather conditions may affect mold growth
Laboratory Tests:
  • Often difficult due to the variation in clinical signs, gross pathological conditions, and the presence of infectious diseases due to immune system suppression.
  • Diagnosis depends on the severity of liver damage
  • Click here for information on approved testing facilities published by the USDA.4
  • Two techniques for detection of aflatoxin:
    • Measurement of AFM1 – quinine adduct in the urine of subjects
      • Presence of this breakdown product indicates exposure to aflatoxin in the past 24 hours
      • This technique only produces a positive result in approximately 1/3 of positive test subjects
      • Also, due to the half-life of the metabolite, the level of AFM1 – quinine measured can vary significantly from day to day, based on diet
      • Not useful for assessing long term exposure
    • Measurement of AFM1 – albumin adduct level in the blood serum
      • Useful for measuring long-term exposure, as blood remains positive for two to three months
Treatment:
  • Aluminosilicate products, such as hydrated calcium aluminosilicate and sodium bentonite, have proven effective in binding aflatoxins and preventing their absorption.
    • Can be added to feed (5 to 10 pounds per ton)
  • Modified glucan based absorbents (Mycosorb, Alltech) also bind aflatoxins; thereby, reducing the levels in feed
  • Affected animals:
    • High quality protein supplements
    • Vitamins A, D, E, K, and B should be increased (toxin binds vitamins and affects protein synthesis)
    • Good management practices to alleviate stress and to reduce the risk of secondary infection (secondary infections must receive immediate attention)
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Economic Consequences and Disease Eradication
Economic Consequences:
  • Medical expenses associated with treatment and, possibly, long-term care
Disease Eradication:
  • Prevention:
    • Reduce plant stress: insects, weeds, diseases
      • Irrigation during pollination
      • Plant corn as early as possible
      • Plant several different hybrids of different pollination periods
      • Store uncontaminated hybrids away from those that are contaminated
    • Harvest corn early and dry immediately (when above 20% moisture content and dry within 24 to 48 hours to moisture content below 14%)
    • Avoid damaged kernels
    • Store corn at 12% moisture content
    • Keep storage and feeding facilities clean
    • Click here for more information published by the Iowa State University. 5
  • Favorable growth conditions:
    • Hot and humid climate
    • Favorable substrate characteristics
    • Factors that decrease a host plant’s immunity:
      • Insect damage
      • Poor fertilization
      • Drought
Aflatoxins and Bioterrorism:
  • In 1989, Saddam Hussein ordered the government of Iraq to begin production of aflatoxin as an economic biological/chemical weapon. The methods used by Iraqi scientists at the Salman Pak facility were crude; Aspergillus was grown on wet rice and the final product was reportedly highly impure. According to UNSCOM estimations, 2200 L of aflatoxin were produced. Some of this material was reportedly loaded into missiles, though this allegation has never been proven as no aflatoxin was found after the 2003 invasion of Iraq by the United States. The presumption is that the aflatoxin was destroyed.8
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Outbreaks
  • 1982: Outbreak of aflatoxicosis in Kenya which included 20 cases with 60% mortality. The daily intake was estimated at about 38 ug/kg body weight for an undetermined number of days.
  • 1974: Outbreak of aflatoxicosis occurred in India. 397 people were affected and 108 people died. The source of this outbreak was contaminated corn, which was reported to contain aflatoxin levels of 0.25 to 15 mg/kg (estimated 55 ug/kg body weight for an undetermined number of days). The patients experienced the following symptoms: High fever, rapid progressive jaundice, edema of the limbs, pain, vomiting, and swollen livers. The appearance of the signs of disease in humans was preceded by a similar disease in domestic dogs, which was usually fatal.
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Sources
Sources:
  1. Alabama Cooperative Extension System. Mycotoxins and Mycotoxicoses. Published on the Alabama A&M Website. Available at http://www.aced.edu/department/grain/ANR767.htm.
  2. FDA, 2005. Foodborne Pathogenic Microorganisms and Natural Toxins Handbook: Aflatoxins. Published on the FDA Website. Available at http://vm.cfsan.fda.gov/~mow/chap41.html.
  3. Food Safety Research Information Office, 1998. Food Safety Research: A Focus on Aflatoxin Contamination. Available at http://fsrio.nal.usda.gov/research/fsheets/fsheet01.pdf.
  4. St. Paul Regional Office, 2005. Aflatoxin. Published by the USDA Risk Management Agency in Saint Paul, MN. Available at www.rma.usda.gov.
    5. Related Articles:
  5. Anonymous, 2005. Aflatoxin in Corn. Published by the Iowa State University Extension. Available at http://www.extension.iastate.edu/Publications/PM1800.pdf. ←
  6. Cassel, E. K., B. Campbell, M.Draper, and B. Epperson, 2001. Aflatoxins: Hazards in Grain/Aflatoxicosis in Livestock. Published by the South Dakota State University Cooperative Extension Service. Available at http://agbiopubs.sdstate.edu/articles/FS907.pdf. ←
  7. Osweiler, G., 2005. Aflatoxins and Animal Health. Published by the Iowa State University Veterinary Diagnostic Laboratory. Available at Aflatoxins and animal health.pdf. ←
  8. Zilinskas, RA. Iraq's biological weapons. The past as future? JAMA 1997;278:418-24. ←
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