Aflatoxins are poisonous and cancer-causing chemicals that are produced by certain molds (Aspergillus flavus and Aspergillus parasiticus) which grow in soil, decaying vegetation, hay, and grains. They are regularly found in improperly stored staple commodities such as cassava, chili peppers, corn, cotton seed, millet, peanuts, rice, sorghum, sunflower seeds, tree nuts,wheat, and a variety of spices. When contaminated food is processed, aflatoxins enter the general food supply where they have been found in both pet and human foods, as well as in feedstocks for agricultural animals. Animals fed contaminated food can pass aflatoxin transformation products into eggs, milk products, and meat. For example, contaminated poultry feed is suspected in the findings of high percentages of samples of aflatoxin contaminated chicken meat and eggs in Pakistan.

Children are particularly affected by aflatoxin exposure, which leads to stunted growth, delayed development., liver damage, and liver cancer. Adults have a higher tolerance to exposure, but are also at risk. No animal species is immune. Aflatoxins are among the most carcinogenic substances known. After entering the body, aflatoxins may be metabolized by the liver to a reactive epoxide intermediate or hydroxylated to become the less harmful aflatoxin M1.

Aflatoxins are most commonly ingested, but the most toxic type of aflatoxin, B1, can permeate through the skin.

The United States Food and Drug Administration (FDA) action levels for aflatoxin present in food or feed is 20 to 300 ppb. The FDA has had occasion to declare both human and pet food recalls as a precautionary measure to prevent exposure.

The term “aflatoxin” is derived from the name of one of the molds that produce it, Aspergillus flavus. It was coined around 1960 after its discovery as the source of “Turkey X disease” Aflatoxins form one of the major groupings of mycotoxins.

Major types of aflatoxins and their metabolites

At least 14 different aflatoxins are produced in nature.Aflatoxin B1 is considered the most toxic and is produced by both Aspergillus flavus and Aspergillus parasiticus. Aflatoxin M1 is present in the fermentation broth ofAspergillus parasiticus, but it and aflatoxin M2 are also produced when an infected liver metabolizes aflatoxin B1 and B2.

  • Aflatoxin B1and B2, produced by Aspergillus flavus and  parasiticus
  • Aflatoxin G1and G2, produced by Aspergillus parasiticus
  • Aflatoxin M1, metabolite of aflatoxin B1in humans and animals (exposure in ng levels may come from a mother’s milk)
  • Aflatoxin M2, metabolite of aflatoxin B2in milk of cattle fed on contaminated foods
  • Aflatoxicol
  • Aflatoxin Q1(AFQ1), major metabolite of AFB1 in in vitro liver preparations of other higher vertebrates

What is Aflatoxin

Aflatoxin is a type of mycotoxin produced by Aspergillus molds. Aflatoxin is probably the most well known mycotoxin, besides trichothecene, and the most researched. This is because aflatoxins are very toxic and highly carcinogenic.

Aflatoxin Symptoms

How badly a person is affected by aflatoxin mycotoxins depends on things like the person’s age, gender, level of exposure, duration of exposure, health, strength of their immune system, diet and environmental factors.

There are two main ways people are usually exposed to aflatoxins. The first is when someone takes in a high amount of aflatoxins in a very short time. This can cause:

  • Liver damage
  • Liver cancer
  • Mental impairment
  • Abdominal Pain
  • Vomiting
  • Convulsions
  • Edema
  • Pulmonary Edema
  • Hemorrhaging
  • Disruption of food digestion, absorption or metabolism
  • Coma
  • Death

The other way people suffer aflatoxin poisoning is by taking in small amounts of aflatoxins at a time, but over a long period. This might happen if a person’s diet has a small amount of aflatoxins, for example. When this happens it can cause:

  • Growth and development impairment
  • Liver cancer due to DNA mutation caused by aflatoxins

Aflatoxin Toxicity

Aflatoxin mycotoxins are toxic to humans and even more toxic to animals. They also cause cancer in humans and animals.

It is believed that eating vegetables like carrots and celery reduces the carcinogenic effects of aflatoxins.

The aflatoxin LD50 rate (the dosage level that causes 50% of a group to die) for animals is between 0.5 and 10 mg/kg of the animal’s weight.

Aflatoxicosis – Aflatoxin Poisoning

The technical term for poisoning by aflatoxin mycotoxins is aflatoxicosis. This usually occurs from eating food contaminated with aflatoxin mycotoxins.

Aflatoxicosis is not contagious and drugs and antibiotics do little to help. Aflatoxicosis damages the liver more than any other organ. Aflatoxin mycotoxins also suppress the immune system.

Aflatoxin Types

There are three main types of aflatoxin mycotoxins:

  • Aflatoxins B: This group includes aflatoxin B1 and B2. Aflatoxin B1 is the most common aflatoxin, as well as the most toxic and carcinogenic.
  • Aflatoxins G: This group includes aflatoxin G1 and aflatoxin G2
  • Aflatoxins M: This group includes aflatoxins M1 and M2. These aflatoxins are metabolic products which are found in the urine and milk produced by animals which have been given feed with aflatoxins in it.

Aspergillus and Aflatoxin Production

Aflatoxin mycotoxins are produced by the Aspergillus species of molds. Aspergillus molds grow mostly on crops, such as grains and nuts. Under the right conditions, Aspergillus often grows on grain before it is harvested. But it can also grow on harvested grain if the grain is stored damp.
Aspergillus also grows on substances like soil, hay and decaying vegetation. The best conditions for Aspergillus to grow on organic materials is when the temperature is warm and when the material has a high level of moisture (7% or more).

Aflatoxin in Food

The American Food and Agriculture Organization estimates that 25% of the food crops in the world are affected by mycotoxins. Of these mycotoxins, aflatoxins are the biggest problem.
Corn, cottonseed and peanuts are the crops most at risk of being contaminated by aflatoxins. Aspergillus also commonly grows on beans, rice, tree nuts and wheat. It grows less often on other grains and nuts.
If animals are given feed contaminated with aflatoxins then aflatoxin mycotoxins can end up in milk, eggs and meat. Aflatoxin M1 and M, which are often found in cow’s milk, are metabolites produced by animals which have eaten aflatoxins.

Aflatoxin Levels in Food

Aflatoxins are found all over the world. However they are much more of a problem in undeveloped or developing nations than they are in developed countries.
Developed countries prohibit high levels of aflatoxin mycotoxins in foods. For example, the United States limits the level of aflatoxins to under 20 parts per billion in food and specifies that the aflatoxins M must be below 0.5 parts per billion in milk.

Chemical processes are used to remove aflatoxins in foods such as nuts, corn, grains and milk. Most foods do still contain very small amounts of aflatoxins though. Although the aflatoxin levels are usually far below the safety limits, this has raised concern about the effects on humans of the long term intake of small amounts of aflatoxins.

Aflatoxin in Pet Food

Pets have died from eating pet foods contaminated with aflatoxin mycotoxins. Between late 2005 and early 2006, 23 or more dogs died from eating Diamond Pet Foods dog food contaminated with aflatoxins.

Peanuts Very Susceptible to Contaminants

One of the most concerning toxins associated with peanuts is a mold that produces aflatoxin. Aflatoxin is a known carcinogen associated with liver cancer. Aflatoxin consumption has also been shown to stunt growth in children. Any food that is creating congestion in the liver may potentially impede its important functions, including detoxification and fat-burning.

Why are peanuts so susceptible to toxins? They are actually legumes, and not nuts. While nuts have a hard, protective shell (think about walnut and pecan shells and just how difficult they are to crack), legumes have a soft, permeable pod. Peanuts also grow underground, because they are part of the plant’s root system. Growing underground with a permeable pod leaves peanuts at the mercy of temperature and moisture conditions including warm humidity that allows for the growth of molds.  Peanuts can also grow molds during storage, shipping, or even on grocery store shelves if the conditions are right for doing so.

How to prevent aflatoxin in corn

In Iowa, problems associated with Aspergillus and aflatoxins are most common in hot, dry years. The fungus survives in crop residue and soil, and produces abundant spores throughout the growing season. Infection of corn by A. flavus and consequent disease development is favored by hot (>86F) dry conditions at pollination and during grain fill. Yellow-brown silks are most susceptible to infection. Injury by insects, hail, drought stress, and early frost expose the kernels to infection. Insects can help spread the fungus within infected ears.

Aflatoxin is a secondary metabolite that is produced by A. flavus under certain conditions. Drought and high temperatures (80 to 105°F) during grain fill are the most common factors associated with pre-harvest aflatoxin production. Warm nights (>70°F) may also increase risk of aflatoxin contamination. Toxin production depends on kernel moisture and temperature. As kernel moisture decreases, aflatoxin production increases. Toxin production is highest at 20 to 18 percent kernel moisture and stops at around 15 percent moisture. The optimum temperature range for aflatoxin production is 77 to 95°F, although production can occur over a wider range of temperatures (52°F to 104°F).

The key to preventing ear rot and storage mold problems is detecting them early, in the field and in the bin. The following practices can reduce the risk of aflatoxin contamination in grain:

  1. Control insects in the field. Second-generation European corn borers and corn earworms damage the ears, allowing for infection.
  2. Early detection can prevent serious losses and avoid crises. Obtain good advance information as to the potential in your area. Scout for aspergillus ear rot from dent through to harvest at 5 to 10 locations in a field. Target areas of the field with plants that appear most stressed. At each location, peel back the husks of 10 ears and inspect them for olive-green powdery mold that is characteristic of the ear rot. If greater than 10 percent of the ears show signs of Aspergillus ear rot, schedule the field for an early harvest. Contact your crop insurance carrier if applicable

If you harvest early based on the presence of Aspergillus ear rot, collect a sample of grain at harvest, as described on page 1, and send to a laboratory for aflatoxin analysis. A list of registered laboratories is available at www.iowagrain.org. The suspect corn should be stored in separate storage until the test result is known; then handle the corn appropriately for the level of aflatoxin you have. Corn from early harvest fields should be dried and cooled immediately to prevent further toxin development. If you have crop insurance, the early harvest and sampling should be coordinated with your insurance adjuster to prevent further growth in check strips waiting for adjustment.

  1. Adjust the combine to minimize kernel damage. Storage fungi infect damaged kernels more easily than intact ones.
  2. Clean bins and grain-handling equipment and remove fines from the corn before storing. Grain debris and dust that collect from storage of grain from a previous season are frequently a source of contamination
  3. After the harvest, sound clean corn can be kept at 16 or 17 percent moisture during the winter. Moldy corn should be dried immediately to 15 percent moisture or less. Holding wet grain for even a short time can allow significant mold and mycotoxin development. For longterm storage into summer, all corn should be dried to 14 percent. Visibly moldy corn is not suitable for longterm storage.
  4. Cool all grain after drying, and maintain it at 35–40°F for the duration of the winter. Aeration is normally used for temperature control. If the corn will be stored during the summer, use aeration to warm it to 50–60°F in the late spring after condensation in bin peaks cannot be controlled. Use aeration to control moisture and temperatures during cool periods in the summer. Next to moisture content, temperature is the most important factor in preventing the development of all molds and toxins.
  5. Control storage insects
  6. Check grain every 2 weeks in storage (more often if quality is suspect) for temperature changes, crusting, hot spots, moisture, and mold. If any of these conditions are detected, steps should be taken immediately to reduce the temperature, aerate the bin, break up hot spots, or remove spoiled grain.
  7. Antifungal agents can be applied to grain to reduce mold growth in storage. These products, such as propionic acid, do not kill the mold already present or reduce toxins already formed. They may have disadvantages, such as restricting use of the corn. If you plan to sell the corn, be certain that antifungal agents are allowable before using them.

 

 

 

 

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