My Co Toxicity

7/30/2019 My Co Toxicity

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SANDEEP K P

AQC-PA1-01


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Introduction

In the last few years there is a trend to replace fish meal as a

source of protein by less expensive sources of protein from

plant origin.

As a result of this trend, aquaculture feeds have a higher risk

of being contaminated with one or more types of mycotoxins.

Mycotoxins are secondary metabolites produced by fungi andhighly toxic to animals

Can reduce growth and adversely alter metabolism of aquatic species


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Molds can infect agricultural crops, particularly cereals and

oilseeds, during crop growth, harvest, storage or processing.

If the conditions for fungal growth and metabolism are right,

mycotoxin contamination is often the result.

Thus, production of toxic metabolites can occur during thegrowth of the crop, during post-harvest storage or during the

storage of the compounded feed.

Moving to plant protein sources in the aquafeed industry

demands careful risk assessment and development of

appropriate protection strategies regarding mycotoxins.


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Different mycotoxins

According to the FAO 25% of the worlds crop harvests arecontaminated with mycotoxins

There are currently more than 400 mycotoxins known.

There are six major classes of mycotoxins that frequentlyoccur:

Aflatoxins

Trichothecenes

Fumonisins

Zearalenone

Ochratoxin

Ergot alkaloids.

They are formed by different kinds of fungi and each fungispecies can produce more than one mycotoxin


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Occurrence of key mycotoxins

MYCOTOXIN PRODUCINGFUNGI COMMODITIES AFFECTED

Aflatoxin A.flavus, A.

parasitcus

Corn, cotton seed, peanut,

soy

Ochratoxin A A.ochraceus, A.nigri,

P.verrucosum

Wheat, barley, corn, oats

etc.Trichothecenes F.graminearum

F.culmorum

Wheat, barley, corn

Zearalenone F.graminearum Wheat, barley, corn

Fumonisin F.verticillioides,

F.proliferatum

Corn

Moniliformin F.moniliforme Corn


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Effects of micotoxins in animals

Immunosuppression

Hematopoietic Effects

Hepatotoxic Effects

Nephrotoxic Effects

Reproductive EffectsTeratogenic Effects

Neurotoxic Effects

Carcinogenic Effects

Dermal Effects

Gastro-intestinal Effects

Performance Effects

Pathological Effects

Residues


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Mycotoxicoses

Mycotoxicoses is the term used for poisoning associated withexposures to mycotoxins.

The symptoms of a mycotoxicosis depend on the type of

mycotoxin; the concentration and length of exposure; as well

as age, health, and sex of the exposed individual.

Mycotoxins are structurally very diverse, a characteristic that

leads to a wide range of symptoms.

Mycotoxins of most concern, based on their toxicity and

common occurrence, are aflatoxin, ochratoxin A, the

trichothecenes (DON, T-2 toxin), zearalenone, fumonisin, andmoniliformin.


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Aquaculture

management

Age, sex and

speciesDuration of

exposure

Nutritional andhealth status

Other toxic

entities

Nature and

level of

mycotoxin

concentration


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Mycotoxins by aspergillus and pencillium moulds

Aflatoxin

Produced byAspergillus flavusand Aspergillus parasiticus.

Aflatoxins are toxic and most carcinogenic substances

known.

Aflatoxins are metabolized by the liver to a reactiveintermediate, aflatoxin M1, an epoxide.

Types

Aflatoxin B1 & B2 : produced byAspergillus flavusand A.

parasiticus.

Aflatoxin G1 & G2 : produced byAspergillus parasiticus.

Aflatoxin M1 : metabolite of aflatoxin B1.

Aflatoxin M2 : metabolite of aflatoxin B2.


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Aflatoxin was the first of the mycotoxins to be investigated in

aquaculture.

Long-term exposure of


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Clinical signs observed in fish fed the aflatoxin-contaminated

feeds were :

Eye opacity, cataracts and blindness; skin lesions; fin and

tail rot; yellowing of the body surface; abnormal swimming

and reduced appetite and feeding.

Histology also revealed damage or gradual deterioration of

the liver.

Since aflatoxin can impair immune function, exposure

increases fish susceptibility to disease.


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Ochratoxin

Ochratoxin A, B, and C are produced by species likeAspergillus ochraceusor Penicillium verrucosum.

Ochratoxin A: the most prevalent and relevant.

Ochratoxin can be present in cereal grains and oilseeds, and

is often formed during ingredient or diet storage.

The key target organ of ochratoxin is the kidney, where it

causes necrotic lesions in the proximal tubules.

In catfish, ochratoxin A has been shown to reduce weight gain

when fed at 1000 ppb for 8 weeks .

Higher inclusion levels (4-8 ppm) significantly reduced feed

conversion efficiency and hematocrit values.

Necrosis was reported in hepato-pancreatic tissue at toxin

concentrations of 1000 ppb and above.


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Cyclopiazonic acid(CPA) sterigmatocystin and versicolorin

Produced by Aspergillus and Pencillium

The latter two are biosynthetic precursors in the production

of aflatoxin.

The toxicity of CPA on channel cat fish found to be greater

than that of purified AFB1 when weight gain is taken as the

criterion.

Resulted in the presence of histological lesions of the trunk

kidneys and stomach.

No haematological changes were observed in cat fish fed

various levels of CPA.


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Fusarium mycotoxins

Trichothecenes and zearalenone

Trichothecenes and zearalenone are produced in temperate

climates by the molds Fusarium graminearumand Fusarium

culmorum.

Zearalenone has estrogen-like activity that has detrimental

effects on the fertility of mammals, although it is probably ofless importance in aquaculture.

Zearalenone could affect reproductive success and the

development of fish eggs, and - zearalenone, one of its

metabolites, has been shown to reduce the number and quality

of sperm in carp .


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Fusarium proliferatum contaminated maize


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Trichothecenes have been intensively researched include

deoxynivalenone (DON), T2-toxin and diacetoxyscirpenol(DAS).

Cause greater reductions in weight gain in juveniles.

Complete feed refusal was observed when dietary DON

concentrations reached >20 ppm.

In shrimp, DON concentrations as low as 0.2 ppm led to

significant reductions in growth rate.


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Fumonisin

Fumonisin have been classified as fumonisin B1,B2,B3 and

B4.

Fuminisin B1 is the most prevalent member of a family of

toxins, produced byFusarium moniliformewhich occur

mainly in maize, wheat and other cereals.

Fumonisin B1 contamination of maize has been reportedworldwide at mg/kg levels.

Fumonisin is of concern to the aquaculture industry because

it commonly contaminates corn and its byproducts.

Fumonisin B1 is hepatotoxic and nephrotoxic in all animalspecies tested.


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Moniliformin

Levels of 20 ppm or more significantly reduced weight gain

compared with noncontaminated control diets.

When feeding moniliformin in combination with fumonisin, a

synergistic negative interaction between the two toxins on

weight gain was observed.


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Fusaric acid

Fusaric acid (5-butylpicolinic acid) is a toxin produced byFusarium verticilloides.

Fusaric acid is usually classified as a phytotoxin with limited

toxicity towards animals.

At toxic levels it causes behavioural responses such as loss of

appetite.

Consumption of fusaric acid elevates brain levels of

tryptophan and serotonin.


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Other mycotoxins CITRININ

First isolated from Penicillium citrinum, but has beenidentified in over a dozen species ofPenicilliumand severalspecies ofAspergillus.

Citrinin can act synergistically with Ochratoxin A to

depress RNA synthesis in kidneys.

ERGOT ALKALOIDS

Ergot alkaloids are compounds produced as a toxic mixtureof alkaloids in species ofClaviceps

PATULIN

Patulin is a toxin produced by the P. expansum, Aspergillus,Penicillium, and Paecilomycesfungal species.


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Mycotoxin effects on immune response

Mycotoxin exposure often decreases disease resistance.

Mycotoxin that impair the immune system include

aflatoxin,T2 toxin,OTA, DON, and fumonisin.

Aflatoxin causes impairment of immune system by inhibition

of protein synthesis.

The effect on the immune system is to reduce the productionof certain cell components such as C4 complement and

lymphokines. eg: interleukins and T lymphocytes.

Aflatoxin suppresses phagocytosis by macrophage which

alters the presentation of antigen to B-lymphocytes.


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effects symptoms

aflatoxi

ns

aflatoxin

s

fish

Carcinogenic Liver tumors, higher incidents of cancer

Decreased

performance

Reduced growth, lower weight gain,

mortality

Hepatotoxic Severe hepatic necrosis, liver leisions

Hematopoietic Impaired blood clotting, anemia

Dermal Pale gills

Nephrotoxic Pale to yellow kidney leisions

shrim

p

Decreased

performance

Reduced growth, low digestibility,

higher mortality

Gastro-intestinal Negative effects on digestive enzymes

Hepatotoxic Hepatopancreatic damage

Hematopoietic Lower hematocrit value


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Efffects Symptoms

Ochratoxin

A

Fish

Decreased

performance

Reduced growth, poor FCR, lower

weight gain, & higher mortality

Hepatotoxic effects Hepatic necrosis, severe liver lesions

Nephrotoxic effects Pale and swollen kidneys

Trichothecenes

Fish

Decrease

performance

Reduced growth & feed consumption,

poor FCR, lower weight gain

Hematopoietic effects Lower hematocrit value & blood Hb value

Shrim

p

Decreaseperformance

Poor growth & lower weight gain

Immunosuppression Decreased resistance to environmental &

microbial stressors

Hematopoietic effects Lower hematocrit value

Fumonisins

Fish

Histopathologicalchange

Lesions in the exocrine and endocrinepancreas

Hematopoietic effects Lower hematocrit value

Nephrotoxic effects Lesions in the inter-renal tissue

Gastro-intestinal

effects

Lesions in the exocrine and endocrine

pancreas


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Some factors which complicate the process of dealing

with mycotoxins are

Mycotoxins affect more than one system simultaneously,therefore producing a multiplicity of responses in the affected

animals. This makes it harder to attribute the response to asingle body system.

The effects observed are not necessarily unique to a given

mycotoxin but may be shared by other toxins and pathogenicorganisms, making it harder to establish a cause-effect

relationship for individual mycotoxins.

Data gathered in experimental studies differ from the natural

intoxications where there are many other factors that can

influence the disease condition.

Also naturally caused mycotoxicoses are often more complex

than those created in experimental studies due to the

interactions between mycotoxins


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Mycotoxin detection methods

These tests usually detect the presence of total aflatoxins ,

fumonisins, DON and OTA.

The ELISA test format is generally employed.

Monoclonal antibody minicolumns are another approach forevaluating the presence of a mycotoxin in a feed ingredient

or feed sample.

This method enables one to easily isolate a mycotoxin and

quantify it by a flurometer or HPLC.


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Mitigation of mycotoxin contamination

Prevention strategies must primarily aim at minimizingmycotoxin formation in the field and during storage.

A significant reduction in mycotoxin formation can be

achieved by good agronomic practices.

For example, the selection of crop varieties that are more

resistant to fungal foliar diseases may reduce fungalinfection and thus mycotoxin formation in the standing crop.

Proper crop rotation, including plowing up harvest residues,

are two of the most effective measures to reduce mycotoxinformation in the field.


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As toxins are generally very stable, they can persist duringstorage, independent of storage conditions, and can hence

reach the final feed.

During storage mold growth and mycotoxin formation can be

controlled successfully by controlling moisture content of thefeed.

If the moisture content is below 12%, molds become

metabolically inactive, and no mycotoxins are produced.


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The incorporation of technical mold inhibitors such as Mold-Zap (Alltech, Inc.) further enhances stability of feed andingredients during storage.

One of the most effective methods of reducing the effects ofmycotoxins is the inclusion of a mycotoxin adsorption agent.

This corrective action can only be taken if the mycotoxinconcentrations are below legal limits.

An effective sequestering agent is one that tightly bindsmycotoxins in contaminated feed without disassociating fromthem in the gastrointestinal tract of the animal.

The toxin-sequestrant complex can then pass safely throughthe animal and be eliminated via the feces, minimizinganimal exposure to mycotoxins.


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Guidelines for evaluating a mycotoxin binder:

1) High level of specificity and affinity for a wide range ofdifferent mycotoxins .

2) No absorption of minerals, vitamins and drugs.

3) Low level of inclusion .

4) Quality control (no contaminants) .

5) Stability over different pH values.

6)Non-toxic, environmentally friendly component.

7) Scientifically tested in controlled in-vitro and invivostudies


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One adsorbent product meeting these criteria is Mycosorb

(Alltech, Inc.), which is derived from the glucan fraction ofthe yeast cell wall.

In the feed and food industry it has become common practice

to add mycotoxin binding agents such as Montmorillonite orbentonite clay in order to affectively adsorb the mycotoxins.

The toxic effects of fumonisin,ochratoxin A,DON and T2 toxin

are not mitigated by most sequestering agents.


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Since not all mycotoxins can be bound to such agents, the

latest approach to mycotoxin control is mycotoxin

deactivation.

By means of enzymes (esterase, epoxidase), yeast

(Trichosporon mycotoxinvorans)or bacterial strains

(Eubacterium BBSH 797), mycotoxins can be reduced.


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Counteracting strategies

Detoxification procedures after harvest should: deactivate, destroy or remove the toxin

not result in the deposition of toxic substances, metabolites or

toxic by-products in the feed

retain nutrient value and acceptability of the feed through the

animal not result in significant alterations in the products technological

properties

destroy the fungal spores

The process should be readily available, easily utilized,

inexpensive and the effects on the environment should also be

considered


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Detoxification procedures

Physical methods Cleaning

Mechanical sorting and separation

Washing

Density segregation

Thermal inactivation

Chemical method

Bases, oxidizing agents and different gases

Biological method

Adsorption

biotransformation


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Biotransformation of mycotoxins by certain isolated microorganisms


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Conclusions

Since the aquafeed industry is moving towards using moreplant ingredients, both risk assessment of mycotoxins as

well as the development of appropriate protection strategies

will become an integral part of aquaculture nutrition.

Prevention strategies must target the production chain from

cropping systems to animal feeding.

Adsorbents that bind mycotoxins and decrease theirbioavailability show a great deal of promise in strategies that

attenuate mycotoxin-induced toxicosis.

It becomes important to have knowledge of not only how tocontrol mycotoxin contamination but also in the event of

exposure of fish to varios mycotoxins to understand how

they are affected.


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REFERENCE

Abdelhamid, A. M., Khalil, F. F and Ragab, M. A.,1998.

Problem of mycotoxins in fish production. Egyptian J. Nutr.

Feeds., 1:63-71.

Diaz, D. E., 2005. The Mycotoxin Blue Book: Mycotoxins in

Aquaculture by Bruce Manning, Page 139-157 Manning, B. B., 2010. Mycotoxins in aquaculture feeds. SRAC

publicationno: 5002.

Santos, G. et al. 2010. Mycotoxins in aquaculture: Occurrence

in feeds components and impact on animal performance.

Monterrey, Mxico, pp. 502-513. www.mycotoxins.info
http://www.mycotoxins.info/http://www.mycotoxins.info/


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My Co Toxicity