Importance Of Aflatoxins In Scientific Sector

By - 09/23/2004

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Ramya Muthukrishnan

Ramya Muthukrishnan

Aflatoxins are the
family of mycotoxins that are related by the presence
of bisfurancoumarin compounds. They are
probably the best know and most intensively researched mycotoxins
in the world. They are named so because they were first isolated from the
fungus Aspergillus flavus.

Recent research has found out thar under specific
conditions some strains of Aspergillus oryzae and Aspergillus parasiticus also have the ability to produce toxins. They
are designated as B and G series because of their fluoresce
green yellow.

The syndrome resulting from the
ingestion of aflatoxin through mold contaminated food
or feed is referred to as aflatoxicosis. The best way
to present aflatoxicosis is to present the infection
of the feed by Aspergillus. High CO2 levels along
with decreased humidity have been shown to decrease aflatoxin
levels. The most effective and practical method of detoxification of
contaminated food is ammoniation. This can kill up to
99% of mold growth. A proper
detoxification process must be technically and economically viable and must
meet the following criteria.

i.
it must destroy or inactivate the aflatoxin

ii.
it should not produce or leave
toxic or carcinogenic residues in the final product.

iii.
it must destroy fungal spores
and mycelia which could under favorable
conditions proliferate and form new toxins.

iv.
it must preserve the nutritive
value and acceptability of the product.

v.
it should not significantly
after important technological properties.

Microbiological Assays

Microbiological
assays seem to be well suited at semi quantitative levels for aflatoxins. Both
genetic and non-genetic effects of aflatoxins are
seen in micro-organisms. Several species
of Aspergillus, Penicillium
and E.coli were found to be inhibited by the toxin.

Details Of
Aflatoxicosis

Causative Agent

Aflatoxins

Nature of acute disease

Aflatoxicosis is poisoning that result from ingestion of aflatoxins in contaminated food or feed. The most pronounced contamination has been
encountered in tree nuts, peanuts and other oilseeds including corn and cotton
seeds.

Nature of disease

Aflatoxins produce acute necrosis, cirrhosis, and carcinoma
of the liver in a number of animal species.
A wide variation in LD50 values has been obtained in animal species
tested with single doses of aflatoxins. For more species, the LD50 value ranges from
0.5 to 10mg/kg bodyweight. Environmental
factors, exposure level and duration of exposure, age, health and nutritional
status of diet can influence the toxicity. Studies show that this aflatoxin requires
metabolic activation to exert its carcinogenic effect and these effects can be
modified by induction or inhibition of the mixed function oxidase
system.

Diagnosis of human illness

Aflatoxicosis in humans has rarely been reported. However, such cases are not always
recognized. Aflaxocisis
may be suspected when a disease outbreak exhibits the following
characteristics.

- The cause is not readily identifiable

-
The condition is not transmissible

-
Syndromes may be associated with certain batches of
food

-
Treatment with antibiotics or other drugs has little
effect

-
The outbreak may be seasonal i.e. weather conditions
may affect mold growth.

The adverse effects of aflatoxins in animals have
been categorized into two forms:

Primary or acute aflatoxicosis
Chronic aflatoxicosis

Associated food

This
includes corn and corn products, peanuts and peanut products, cotton seed,
milk, tree nuts such as brazil nuts, pecans, pistachio
nuts and walnuts. Other grains and nuts
are susceptible but less prone to contamination.

Relative frequency of disease

The relative frequency of aflatoxicosis in humans in US is not known. No outbreaks have been reported in
humans. Sporadic cases have been
reported in animals.

Course of disease and
Complications

Epidemiological
studies reveal that there is high incidence of hepatoma
and an association between cancer incidence and aflatoxin
content of the diet. According to one
report, a village in northwest

India

encountered the disease of aflatoxicosis. Three hundred and ninety seven persons were
affected and 108 persons died. This
outbreak was due to contaminated corn and aflatoxin
levels were 0.25 to 15mg/kg was found.
The daily aflatoxin B1 intake was estimated to
have been 55 mg/kg bodyweight. The
patients experienced high fever, rapid progressive jaundice, edema of the
limbs, pain, vomiting and swollen livers. A 10 year follow-up found that the survivers
fully recovered with no ill effects from the experience.

Target populations

Very
little information is available on outbreaks of aflatoxicosis
in humans because medical services are less developed in the areas of the world
where high levels of contamination of aflatoxins
occur in foods. Therefore these cases
may go unnoticed.

Areas Of
Current Research And Future Research Activities

Preharvest contamination of aflatoxin
is influenced by soil moisture and fertilizer level. The optimum levels, methods and time of
irrigation as well as optimum fertilizer application at which Aspergillus infection does not occur have to be worked for
various crops. Development of such
agricultural practices will prevent the aflatoxin. contamination.

Breeding
and selection of resistant varieties of crops will help in prevention from aflatoxins.

Development
of rapid, accurate and precise methods is essential for quantitation
of aflatoxin during various stages of production,
processing and marketing of agricultural commodities.

Simple
rapid screen methods suitable under field condtions
should be developed.

The
procedures for decontamination and detoxification of contaminated products will
have to be improved.

The
relationship between aflatoxin ingestion and various
human diseases need to be established and the role of malnutrition in
manifestation of toxic effects to aflatoxin has to be
established.

Regional
training centers may be established to train manpower in all the aspects of aflatoxin problem which would help to reduce the human and
animal exposure to aflatoxin.

Research Today

The
advent of
biotechnology, genetic engineering techniques could be used to incorporate
antifungal genes into specific plant species.

The composition of many cereals
and crops can be altered using genetic engineering to improve the diversity of
varieties available for food processing.

A better adaptation of plants to
specific environmental conditions can be gained using genetic engineering
techniques.

Genetic modifications could lead
to an increased disease and pest resistance and to the production of new
cultivars with improved pest and disease resistant to promote more
environmentally acceptable alternatives for food production.