Fungal Intoxication in Food: Mycotoxin (Aflatoxin) Poisoning

Mycotoxins are poisonous fungal metabolites of which, aflatoxins are the most prominent. They are produced when someone ingests fungal-infested food and can be very toxic, even lethal. Aflatoxins are the biggest threat of all forms of fungal intoxication on food.

Several fungi that produce these mycotoxins and they target many foods such as cereals, fodder crops, and even hay.

The following factors favour their growth, multiplication, and reproduction:

1. Air and humidity (≥ 70 percent)
2. Temperature conditions (between 10°C and 30°C)
3. Cereal damage (pre-disposing factor)

These conditions create a perfect environment for the thrift of these fungi, which spoil food by rendering the food not fit for consumption. They are produced in cereals in the field and during storage when the temperatures are high and the levels of humidity are elevated.

Aflatoxicosis (the most critical form of fungal intoxication in food)

This is the disease that arise as a result of aflatoxin poisoning. It can occur in both man and animals and it produces chronic signs in acute doses. It was first discovered in early 1960 in turkeys and ducklings.

Aetiology

It is caused by the fungus Aspergillus flavus. The common toxins produced include B1, B2, G1, and G2, which are direct action toxins. Contamination of commercial cereals can be catastrophic.

Indirect toxins such as M1 and M2 can also affect man by consuming products (e.g. milk) from animals with afflatoxicosis. Due to their mode of action, they are generally labelled as factors.

Aflatoxin is thermo stable but alkaline labile.

The most vulnerable species are all animals with pets taking the heaviest blow due to their small sized bodies. They catch the poison from contaminated food.

In larger species, the young ones will be adversely affected. All humans suffer the same severity unless one has compromised immunity.

However, aflatoxins in meat is generally not considered a very big problem.

Signs and symptoms of aflatoxin poisoning

Since aflatoxin poison affects the liver, other symptoms arise from the liver failure. Aflatoxins are carcinogenic and induce tumour formation (in chronic cases).

The observable symptoms include:

1. Abdominal pain due to infection of the liver
2. Ascites (fluid collects in the abdomen leading to formation of a distention/swelling)
3. Severe jaundice
4. Severe weakness
5. Hepatic necrosis followed by haemorrhage
6. In acute cases, liver fibrosis occurs. Without intervention, the cell death my progress and cause tumour formation.

Diagnosis

Clinical signs and health history can be associated with mouldy food/feed. To confirm the presence of the toxin, it is isolated from the feed and animal tissues (especially the liver).

Control measures

Proper harvesting techniques and rapid post-harvesting drying of cereals.

Control of temperature and humidity during storage and transportation of cereal foods. Use fungicides.

Monitor the hygiene of animal feed. Control mould growth on the animal feed (e.g. hay and silage). Do not feed animals on aflatoxin-infested cereals.

Poisoning in Animals

Animals get poisoned via two major routes:

By ingesting the preferred poison

Through secondary poisoning by ingesting the poisoning agents. The plants they feed on may also be toxic, causing either primary or secondary poisoning.

Classes of poisoning in animals

1. Biological toxins that arise from plants, animals, fungi, etc.
2. Chemo toxins that arise from chemicals such as pesticides and acaricides, which cause cyanide poisoning.

Diagnosis of animal poisoning

Only a qualified person should do the diagnosis since the outcomes do have legal implications.

Records are important since history plays a critical role in diagnosis, especially in cases where the feed is the suspect.

Clinical signs are also important since most poisoning cases usually end in fatality. Post mortem is advised.

Laboratory analysis will confirm the suspicions.

Sampling rules for laboratory analysis

• The sampling technique depends on the suspected poison
• Use clean and sterile container for the samples
• Take a fresh sample
• Proper handling to avoid any contamination or cross-contamination
• Avoid spillage or contact with persons involved
• Do proper storage (freeze the sample if it will take some time to reach the laboratory).
• Ensure that as few people as possible touch the sample before it reaches the lab
• Properly label the sample to avoid any mix up
• Do proper recording after submitting the sample

General clinical signs

1. Very few cases of poisoning in animals have pathognomonic signs
2. General sudden death affecting several animals
3. Sub-normal temperatures depending on the route of transmission
4. Oral poisoning usually exhibits abdominal pain, excessive salivation, weakness, and muscle tremors/twitching.
5. Poisoning through the skin leads to reddening of the skin and diarrhoea.

General post mortem signs

1. Organ congestion/haemorrhage
2. Gastroenteritis/inflammation of the entrails
3. Liver and kidney enlargement
4. Hyperaemia on the skin

Treatment for poisoning

1. Remove the animal from the poison/poison from the animal (whichever is applicable in your case) and ensure that the animal is comfortable.
2. Prevent any further absorption of the poison through gastric lavage, use of activated charcoal, or washing with plenty of clean water.
3. Treat the symptoms or provide an antidote to neutralize the poison.

Biological poisons tend to be plants, usually the drought resistant types.

Chemical poisons may include:

• Acaricides – animals will consume it when used at the wrong time and get arsenic poisoning
• Dressing chemicals for seeds cause mercury poisoning
• Urea poisoning from the concentrates the animals feed on. If you use urea in silage, there is risk that you will end up poisoning your animals.
• Other plants like sorghum will cause cyanide poisoning.

Physical poisoning agents include:

• Lead and copper that are most commonly used with agricultural products
• Lightening
• Sun stroke – during high temperatures. The animal can also suffer from photosensitization when there is very bright light.

Food animals (animals generally consumed as food) may cause secondary poisoning. It will pass the poison to the secondary consumer through their tissue.

For that reason, here is what you need to do when checking for an animal to eat:

1. Check the viscera. If they are darker than usual, avoid such meat.
2. Avoid eating animals of unknown origin
3. Be very selective when eating marine foods, they are usually toxic
4. Examine fish before cooking. There are poisonous and non-poisonous types.