Mycotoxins are toxic compounds produced by fungi .They are secondary metabolites of fungi which are associated with certain disorders in animals and human beings.. Unlike bacterial toxins, fungal toxins (mycotoxins) are not proteins and therefore are not usually detectable by the immune systems of humans and animals. Lack of visible appearance of fungus does not negate presence of mycotoxins. Toxins can remain in the organism after fungus has been removed. They can be heat stable, not destroyed by canning or other processes. Today 300 - 400 mycotoxins are known. Mycotoxins that are of human concern based on toxicity are Aflatoxin, Deoxyniva-lenol (DON) or Vomitoxin, T-2 toxin, Zearalenone, Fumonisin and Ochratoxin A.
These are highly toxic carcinogenic secondary metabolites produced by fungi namely Aspergillus flavus, Aspergillus parasiticus and Aspergillus nomius. Its sources are Corn and Groundnuts. Temperature : 25-30°C and grain moisture favour production of Aflatoxins. Naturally produced Aflatoxins are B1, B2, G1, G2. They undergo modifications during cellular metabolism and processing of foods to produce several derivatives such as M1, M2, P1, etc. Aflatoxicosis is caused by high doses in short intervals or low doses in high intervals
DON and T-2 Toxin
These are field toxins not storage toxins.They target the circulatory, alimentary, skin, and nervous systems. Fusarium graminearum produces DON and T-2 Toxin which causes scab damage to kernels and head blight. Optimal temperature range is between 70 and 85 degrees Farenheit. Advisory level of DON is 1 ppm.
These are produced by fungi namely Fusarium roseum, F.graminearum, F. poae and F. culmorum.Food affected is corn, wheat, barley, oats. Zearalenone has estrogenic effects
These are produced by fungi namely P. Verrucosum and A. ochraceus. Food affected are Cereals, coffee beans, and grapes. Ochratoxin can be transmitted from pork to humans by eating pork that is fed with contaminated food. Ochratoxin sources are gnuts, pecans, beans, dried fruit and dried fish.
EFFECTS OF MYCOTOXINS
Mycotoxins are metabolized in the liver and kidney and also in the digestive tract. Fungal contamination affects both the organoleptic characteristics and the alimentary value of feeds and entails a risk of toxicities
Residual effects in Humans (Food Safety Risk)
Ø Physiological and pathological changes
Ø Food poisoning
Ø Inhibition of protein synthesis & Alteration of capacity of cells to proliferate
Ø Increase of tryptophan in blood and brain (affects appetite, muscular co-ordination and sleep
Ø Nausea ,Vomiting, Headache
Ø Abdominal pain, Diarrhea, Giddiness, Convulsions
Ø Reproductive and mammary changes
Ø Role in hormonal imbalance and breast cancer
Ø Precocious pubertal changes in children
Ø Carcinogenic effects
Effects on Production
> Chickens, turkeys, and ducklings are affected by ochratoxicosis, causing poor weight gain, egg output, egg size/weight and poor shell quality.
> In poultry, causes reduced egg production, beak and oral lesions, lower carcass value and abnormal feathering
> Produces a thiaminase causing thiamine deficiency in Chicks.
>Mycotoxins are also known to interfere with the utilization of dietary vitamins D and this may result in deficiency symptoms of the vitamin
>Increase in mortality of birds
Effects on Organs
Positive correlations in weight for liver, spleen and kidneys (organ’s enlargement)
negative correlation for bursa of Fabricius and thymus (organs' reduction)
change in texture and coloration of liver and bursa of Fabricius
Symptoms of Mycotoxicosis
1. Drugs and antibiotics are not effective in treatment.
2. The symptoms can be traced to foodstuffs or feed.
3. Testing of said foodstuffs or feed reveals fungal contamination.
4. The symptoms are not transmissible person to person.
5. The degree of toxicity is subject to persons age (more often in very young and very old), sex ( more often in females than males)and nutritional status.
6. Outbreaks of symptoms appear seasonally
PREVENTION AND CONTROL OF MYCOTOXINS
The presence of mycotoxins is unavoidable as they are environmentally induced. However, the economic importance and health implication of mycotoxins has made its control inevitable. Control is very important to the feed manufacturer and livestock producer. Application of Good Agricultural Practices (GAP), Good Manufacturing Practices (GMP), Good Hygienic Practices (GHP) and Hazard Analysis and Critical Control Points (HACCP), Crop Rotation and mold growth can be inhibited by appropriate drying and storage of grains/feeds.
Some more Efficient detoxification strategies are as follows :
1. Detoxification and Physical treatment
´ Exposure to sunlight for about 12-14 hours degrades aflatoxin up to 70-90%
´ Drying at 120°C for 2-3 hours resulting in reduction by 60-90%
´ Autoclaving, pelleting to inhibit mould growth.
´ Cleaning, mechanical sorting and separation
´ Density segregation (floatation).
2.Chemical Agents like Alkali, Calcium Hydroxide, Sodium Hydroxide, Ammonia, Acids Benzoic acid and Copper Sulphate at 0.04 – 0.05% can be used.
Mycotoxins affects nutrient value of feed, increasing the dietary level can minimize this effect.
4. Use of Adsorbents/binders
´ Inorganic toxin binders (Silica based) like Zeolites, Bentonites, Aluminosilicates , Activated charcoal, Clay and Yeast or Hydrated Sodium Calcium Aluminosilicate (HSCAS) at 1%
´ Organic toxin binders (Carbon based) like Oat hulls, Wheat bran, Alfalfa fiber, Extracts of yeast cell wall, Cellulose or Hemi-cellulose and Pectin can be used.
Regulation should be based on surveillance, evaluation of risk assessment, establishment of tolerance level (or LD50) and enforcement of compliance with this level for raw materials and finished feed.
Thus the enforcement of the NIAS recommended minimum aflatoxin level in feed ingredients and finished feed is very essential
PREVENTION AND CONTROL OF MYCOTOXINS
The presence of mycotoxins is unavoidable as they are environmentally induced. However, the economic importance and health implication of mycotoxins has made its control inevitable. Control is very important to the feed manufacturer and livestock producer
Future Fight Against Mycotoxins
Ø Have farmers select strains resistant to contamination.
Ø Scientists hope to genetically engineer plants resistant to fungal infection.
Ø Use feed additives that sequester the toxins and prevent absorption from the gastrointestinal tract.
Considering the importance of mycotoxin in food safety, international trade, public health and the performance of poultry and livestock, the need to have a regulatory framework that addresses mycotoxin cannot not be over emphasized. Mycotoxin must be addressed at the policy level. This is not an option but a must.