Mycotoxins, Antibiotics, Growth Promoters

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Mycotoxins, Antibiotics, Growth Promoters

JoAnn Guest

Jan 26, 2005 19:32 PST

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Animal husbandry has numerous facets, and great changes in farming

practices as well as an enormous expansion in the pharmaceutical

industry, have changed the face of the animal-products industry over

the past decades.

 

Particularly the use of drugs has had a profound influence on animal

husbandry. Drugs are not only used to curtail

disease but they are also extensively used to stimulate growth, and

this last factor has led to an unprecedented increase in the use of

drugs.

http://www.amazingdiet.org/

 

Antibiotics

 

Antibiotics have had a profound effect on the agricultural sector,

and today antibiotics are used extensively in animal husbandry.

Antibiotics are not only administered to animals for the treatment

of disease, but subtherapeutic doses of these antimicrobials are

administered routinely for growth promotion in livestock and poultry

production.

 

Antibiotics are also used in wildlife, and for

the control of plant diseases and food spoilage.

 

In the United States alone some 15 million pounds of antibiotics are

administered to farm animals annually. The fact that animals grow faster

when receiving subtherapeutic doses of antimicrobials serves as an

incentive to farmers to administer these products, particularly

since an added benefit is found in disease prevention.

 

Although vehemently denied in some quarters, this practice is giving

rise to a new generation of antibiotic-resistant microbes which can

cause

serious outbreaks of disease among humans. Infectious diseases

account for millions of deaths annually, with respiratory

infections, diarrhoeal diseases and tuberculosis accounting for the

majority of these.

 

Drug-resistant bacteria have accounted for a steady increase in the

incidence of human Salmonella infections, and in 1983 an outbreak

of Salmonella infection in the Midwestern states of the USA was

actually traced to the farmyard from which the disease spread

An epidemiologic investigation in Minnesota revealed that patients

had eaten ground beef (hamburger) and that the meat had come from a

farm lot where cattle had been fed subtherapeutic quantities of

" chlortetracycline " for growth promotion and disease prevention.

In outbreaks of gastrointestinal disease from drug-resistant

bacteria, it is a common occurrence that infected patients had taken

antibiotics for other diseases such as bronchitis, pharyngitis,

otitis media (ear infection) or other non-diarrhoeal diseases prior

to the onset of the gastrointestinal disease.

This suggests that whilst patients are on antibiotics, and they consume

foods injected with resistant bacteria, the destruction of the natural

non- resistant intestinal bacteria offers some selective advantage to

the

drug-resistant varieties which then flourish and become pathogenic.

The symptoms are normally diarrhoea, abdominal cramps, nausea and

vomiting and in some cases chills, fever, and confusion.

Futhermore,

the disease is difficult to treat, as the bacteria will not respond

to drugs in view of their antimicrobial resistance, and death can be

the ultimate result, even in hospitals with all the necessary care

facilities.

The fact that antibiotics are widely used in hospitals, accounts for

the fact that outbreaks of antimicrobial-resistant bacterial

infections are largely recorded in these institutions.

Bitter rows have developed over this issue between governments and

trade organizations.

In Germany and Denmark the antibiotic avoparcin, which farmers inject

into their livestock, was banned because of

concern that antibiotic resistance could spread from the farmyard to

hospitals. Brussels, on the grounds that the ban could interfere

with free trade, declared the ban illegal.

Avoparcin is similar to other antibiotics such as vancomycin and

teicoplanin which are the only drugs available that kill

methicillin-resistant Staphylococcus

aureus (MRSA), which is becoming more and more prevalent in

hospitals.

Microbiologists were dismayed that the German studies had

not been able to uphold the ban.[iii] Sadly it is often the elderly

or infants who succumb to the disease due to their weaker

constitution.

In view of the widespread use of antibiotics in animal husbandry,

the most common sources of contamination, by this new breed of

antibiotic resistant bacteria, are poultry, cattle, calves,and

milk.

In fact, in over two thirds of US outbreaks of multiple drug-

resistant Salmonella infections with a definite source, the bacteria

came from food animal populations, and the transmission of resistant

bacteria to man, through the consumption of food animals, is thus

not a rare event.[iv]

The World Health Organization has reported that resistant strains of

Salmonella typhimurium have increased

dramatically in many countries, and there was hardly any medication

that was effective against the DT 104 strain of this species. In

some European countries the total number of Salmonella infections

has increased 20fold in the last decade and in Britain, where DT 104

was first isolated in 1988, the number of infections caused by this

strain rose from 10 to 18% within the year 1996 alone.[v]

Tetracyclines are the most commonly used antibiotics in feeding

operations, and these drugs commonly occur in the animal products

purchased from supermarkets and other stores.

Contamination of foods with antibiotics may present various health

hazards and can be strongly allergenic in sensitive individuals.

A study on the occurrence of antibiotic residues and drug-resistant

bacteria in beef and chicken tissues purchased from supermarkets in

Hermisillo,

Mexico, showed that 86% of beef samples were contaminated with

" streptomycin " whilst other antibiotics were also prevalent.

Chicken breasts sampled, likewise, showed high levels of contamination

which exceeded FDA " tolerance " limits.

In this study it was found that in more than 50% of the chicken and

beef samples investigated, more than one antibiotic was present at

the same time,

and in some cases three or four different antibiotics

had been administered to the animals " simultaneously " (Fig. 4.13).

The frequency at which the different microorganisms occurred in the

samples varied, but a wide range of potentially pathogenic species

was prevalent in both beef and chicken samples (Fig 4.14).

From table 4.7 it is evident that no penicillin was found in any of

the samples investigated. The reason for this is that penicillin is

no longer used subtherapeutically in these areas as it has become

ineffective.

Bacteria resistant to penicillin were however isolated

from these tissues, showing that " drug resistance " persists beyond the

time in which the drugs were used. Nearly all the bacteria isolated

from the above mentioned tissues were resistant to penicillin, with

high resistance to tetracycline and streptomycin also noted.

In view of the current controversy surrounding the issue of

antibiotic resistant bacterial strains, two questions seem vital at

this stage:

1) Is the use of subtherapeutic doses on farms responsible for the

increase in resistant strains?

2) What is the status regarding vancomycin resistance?

The argument by industry has been that subtherapeutic doses cannot

enhance resistance, however, this does not seem logical as even low

doses of antibiotics should provide a selective advantage to

resistant strains.

If indeed this is the case, then at least certain antibiotics should be

banned for use in the animal husbandry industry.

Vancomycin is a case in point, as vancomycin is the only drug that can

kill methicillin-resistant Staphylococcus aureus which

is causing hospital epidemics with alarming regularity.

To examine this issue, a project was jointly undertaken by the

Departments of Zoology and Microbiology at the University of the Western

Cape, in

which chicken, pork, beef and milk samples were tested for bacterial

contamination and multiple antibiotic resistance in the greater Cape

Town area.

Animal bacterial samples were taken at abattoirs and at retail outlets,

the rationale being that differences in resistance

between the two groups of samples taken at the beginning of the

slaughtering cycle would indicate that the resistance had emanated

from the farm. The results for the chicken samples have thus far

been evaluated, and are presented in table 4.8.

The results clearly show that a large proportion of the bacterial

strains showed multiple antibiotic resistance, and in most cases the

bacteria from the abattoir samples had a higher resistance to

antibiotics than the retail samples thus indicating that the

resistance route came via the farm. The very high resistance level

displayed by most of the bacteria is certainly unsettling.

Staphylococci were resistant to tetracycline and oxacillin but the

percentage of abattoir isolates that displayed simultaneous

resistance to both tetracycline and oxacillen was nearly double that

of retail samples (69.6% versus 39.4%).

Gram positive bacteria (Staphylococcus) are susceptible to vancomycin,

and although resistance of Staphylococcus to vancomycin as well as

methicillin

was not very high, even the 7% resistance recorded in retail samples

is cause for concern, considering that this is the only drug that

can kill methicillin-resistant Staphylococcus aureus.[vi]

Producers are required to observe a withdrawal period after

administering antibiotics, prior to marketing their product. It is,

however, not feasible to monitor all the meat that goes to market,

and studies on swine have shown that producers do not adhere to the

specified withdrawal times.[vii]

Antibiotic residues are even found in carcasses of cattle with no

record of antibiotic treatment.[viii]

Even if they should adhere to these withdrawal times, it is doubtful

whether this will be of much benefit, considering the fact that

resistance has been maintained over years to antibiotics that are no

longer in use.

Besides the antibiotic problem, contamination of carcasses with

antimicrobial agents and other dangerous compounds

such as " heavy metals " , " organochlorine compounds " and " growth

stimulants " , is now so widespread that methods are being devised to

routinely monitor these contaminants

in the interest of human safety.

Additional Growth Promoters

Besides the addition of antimicrobials to promote growth, animal

feed is also routinely spiked with " hormonal growth " promoters of

which some may be " carcinogenic " .

Hormone residues that have been isolated from beef are used as anabolic

steroids to promote weight increase.

To promote lean meat production, animals are fed ß- agonists, a group of

drugs that convert fats to fatty acids and stimulate the formation of

proteins, to promote rapid weight gain.

In addition in some countries growth hormone is administered and

even genetically-engineered hormones are used, such as PST, which is

used to promote lean meat production in pigs.

Some of these growth promoters, such as clenbuterol, are banned, but

there is a healthy black market trade in these growth-promoting drugs as

shown by the clenbuterol scandal in 1996 when German authorities found

that the

drug was being used on more than 40 calf fattening farms in

Nordrhein-Westfalen and consequently prohibited the slaughter of

2400 calves and arrested a veterinary drug dealer.

In a further case around the county of Gütersloh, calves were found with

the banned

antibiotic Chloramphenicol.

Farm animals today are often treated as commodities, like inanimate

consumer goods. They are frequently housed in unhealthy environments

and fed virtually anything that will promote growth and increase

profits, even though the long-term effect on the health of the

animals or the human consumer is not known.

In large chicken hatcheries the chicks never see sunlight, but are

subjected to low- intensity light for close on 24 hours per day. The

lights are switched off only for approximately 15 min each day so that

the chickens can get used to darkness, lest they panic during a power

failure and cause production losses. Animals are cramped together to

limit their movements and energy expenditure, because growth and

mass increase are the paramount criteria that are taken into account

when designing these facilities. New breeds of chickens are selected

for growth performance with virtual disregard for all other

parameters.

In the past, a free range chicken could be assumed to consume

approximately 17 kg of feed to grow to a market mass of

1.5kg. Today, some breeds utilize only 3.5 kg to achieve the same

mass increase, and this in only six weeks.

The chickens are geared for rapid growth, but their other systems are

severely compromised.

The cardiovascular system, internal organs and immune systems are

poorly developed so that extreme care must be taken not to induce

stress or exposure to infectious bacteria lest they die before

reaching market size.

Farm animals are fed carcass meal, fish meal, edible plastic,

sewage, petro-chemical residues and excrement.

On some farms veritable food chains have been set up where chicken

manure, brom battery chickens, is fed to the sheep cand cattle, and dead

chicks and unhatched eggs in turn are the feed items used in the

piggery.

In the chicken industry, the slaughter offal such as entrails, legs

and heads are often dried, ground and recycled as feed, thus

effectively turning the chickens into cannibals.

Moreover, the chickens are routinely manipulated with a host of " growth

stimulating " , antimicrobial and digestibility enhancing drugs.

Prion diseases

Prions cause a group of animal and human neurodegenerative diseases

which are now classified together because of their etiology and

pathogenesis.

The infectious agent is not a virus, nor does it contain DNA sequences,

it is a brain protein which has undergone

modification.

Prion proteins are thus thought to exist in two forms,

the benign Prion protein (PrPc) and the infectious `scrapie form'

(PrPSc).[x]

The normal Prion protein consists of strands of amino

acids twirled into helices whereas in the infectious form the amino

acid strands are flattened into ß-sheets which can cause

transmissible dementias.

Transmissible dementias are degenerative conditions associated with

neuronal loss, and neuronal vacuolation

or spongiform (spongy) changes. Furthermore, the changes are

accompanied by the accumulation of the abnormal proteinase-resistant

prion protein known as PrPSc which has undergone posttanscriptural

changes, and the ensuing disease is thus termed a prion disease.

Prion disease is becoming a high-profile public health issue,

particularly since the Bovine Spongiform Encephalitis (BSE) or " mad

cow's disease " epidemic rocked Britain. Beginning in 1986, this

previously unknown prion disease decimated the beef industry in

Britain and it has been proposed that some 160 000 cattle were

affected.

The infectious agent was probably transferred to the

animals by routinely feeding them meat and bone meal dietary

supplements.

Carcass meal is predominantly prepared from animals

that have died of disease, or animals that have been condemned at

the abattoir as unfit for human consumption.

The carcass meal and excrement is heat-sterilized to kill the bacteria,

but recently chemical sterilization has become the method of choice in

many

countries, as it is cheaper. Since 1988 the feeding of dietary

protein supplements derived from sheep or cattle offal has been

banned in Britain and it is argued, that this step has brought the

epidemic under control. The incidence of reported cases has indeed

declined since the peak was reached in 1992.

Spongiform encephalopathies are tranmissible dementias, and occur in

man as Creutzfeldt-Jacob disease (CJD), Gerstman-Straussler

syndrome, and kuru. In other animals it occurs as scrapie in sheep

and transmissible mink encephalopathy in ranch mink.

In the UK alone some 75 000 people per year die demented, of which 50%

have Alzheimer's disease and 2% have Creutzfeldt-Jacob disease.[xi] The

latter disease is characterized by a sudden onset of disease, with

rapid progression through dementia and death within a year.[xii]

Economic pressures led to initial denials that consumption of BSE

contaminated beef could lead to Creutzfeld-Jacob disease, but in

1996, after a decade of ministerial denials the British Government

reluctantly admitted the link between the two.[xiii]

Since this

time, European governments have reacted strongly, banning British

beef [xiv] and even slaughtering thousands of head of cattle to

restore consumer confidence. In Switzerland the government

subsidized the slaughter of 230 000 cows born before 1 December 1990

to restore faith in Swiss beef.[xv]

Prior to the admission that there was a link between BSE and CJD it

was argued, that cross species contamination was not possible and

that one could not contract the disease from eating contaminated

food. However, instances of exotic animals in captivity with

transmissible dementias have been linked to consumption of meat and

bone meal, and instances in domestic cats in the UK are assumed to

be due to BSE-infected offal in cat food.[xvi]

In early 1996 it was

recognized that the new variant of CJD that was affecting 12 young

persons in the UK had been transmitted via BSE contaminated beef.

The experimental transmission of the disease by inoculating macaques

(Old World monkeys) with BSE infected brain homogenate proved that

cross species transmission was possible,[xvii] and it is now even

well established that transmission occurs between infected cows and

their calves thus raising questions about the future of the epidemic.

[xviii]

It has been argued, that what happened in Britain is but the tip of

the iceberg, and that major epidemics could erupt worldwide.

Thousands of Europeans could be unknowingly infected with the

disease and could die, and even in the US some researchers feel that

the conditions which led to the UK outbreak can lead to similar

events in the USA.[xix]

Statistics already suggest, that BSE is now

Europe-wide and by May 1996 Switzerland had reported 211 cases of

BSE, Eire 125, France 18, Portugal 30, whilst a total of 71 706

tonnes of British meat and bone meal and 33 424 breeding bovines

have been exported to EU member states from 1985 to 1990.[xx]

Mycotoxins

Regulations regarding animal feeds are not as stringent as those

regarding food for human consumption, and feed that is contaminated

with

" mycotoxins " can be a further source of disease if fed to farm

animals.

Mycotoxins are toxins produced by fungi, and contaminated

foodstuffs is a major problem in most tropical and subtropical

countries.

Aflotoxins are fungal toxins and constitute a serious

worldwide problem. Aflotoxins contaminate peanuts, nuts, rice,

grains, soya beans, peas and sorghum seeds, all of which can end up

as animal feed.

Aflotoxins AFM and AFM2 are the most potent liver

carcinogens in rats, producing 100% incidence of liver tumours in

rats at a dosage of 95 g/kg. These aflotoxins have been found in

liver, milk, blood and kidneys of animals fed aflotoxin-contaminated

feeds.[xxi]

Contamination of the animals does not end at the farmyard, but

continues in the slaughterhouses of the world. Abattoirs are

concerned with speed rather that the well being of the animals, and

stress and terror are endemic.[xxii]

Carcasses are contaminated by faecal bacteria when they come into

contact with ruptured intestines or fall on the ground. Because of

contamination with the faecal

bacteria Yersinia enterocolitica, Campylobacter spp., Salmonellae

and Aeromonas hydrophila, as well as residues of veterinary drugs

and mycotoxins, it has even been suggested that carcasses be

" decontaminated " by radiation to combat the health hazards.[xxiii]

Genetic Engineering

Genetically engineered livestock is expected to revolutionize the

agricultural industry. It is envisaged that animals can be made to

grow faster and to incorporate changes in fat composition so as to

be more suitable for human dietary needs.

Gene transfers have been carried out on laboratory animals, but have

also recently been extended to domestic animals.

Most studies have centered around growth-regulation, as studies in mice

have shown that gene transfers of bovine, ovine, rat or human

" growth-hormone " genes can almost double the rate of growth in mice.

Transgenic farm animals already

include chickens, cows, pigs, sheep, rabbits and fish. Human, Bovine

and rat growth-hormone genes have been transferred to pigs, but the

mortality rates in these animals is high.

Leaner meat has been produced in transgenic pigs, but at a price.

Transgenic animals suffer from a variety of pathological changes

which shorten their lifespan.

In pigs it was found that the animals were lethargic, and suffered from

lameness, uncoordinated gait,

protruding eyeballs and thickened skin. Moreover, they suffered from

gastric ulceration, severe wynovitis, degenerative joint disease,

pericarditis and endocarditis, cardiomegaly, parakeratosis,

nephritis and pneumonia.[xxiv]

The risk of disease from contaminated animal products today is indeed

something to consider. In the past the major concerns revolved around

infectious diseases and parasitic

and viral infections.

This risk still exists today, but additional risk factors have been

added through modern animal husbandry.

Modern technology has also had its effect on plant foods, with gene

transfers being currently in vogue. The long term effects of these

manipulations are also not known and these products may also be

viewed with some degree of scepticism.

However, man has to eat, and if a choice has to be made between

manipulated plant or animal foods, the consumption of plant foods would

certainly be associated with lower risks of contracting diseases.

A diet free from animal products, and concentrating on a variety of

fresh whole foods will supply excellent nutrition and will at the same

time protect against

many of the modern ills associated with the Western diets. Such a

diet need not, and indeed should not, be less attractive than a diet

based on animal products.

A little ingenuity with emphasis on variety will provide an exciting,

healthy lifestyle.

The above has been excerpted from the book Diet and Health by

Professor Walter J. Veith available through our webstore.

---

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[iv] Holmberg, S.D., Wells, J.G., Cohen, M.L. 1984. Animal-to-Man

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[v] Ärzte Zeitung 1997. Zahl resistenter Salmonellen nimmt

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retail chicken in South Africa. Lett. Apl. Microbiol. (in Press)

[vii] Salisbury, C.D.C., Chan, W., Patterson, J.R., Mac Neil, J.D.,

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[viii] Eriksen, J.O. 1990. Antibiotic contamination via the

veterinary surgeon as a possible cause of detection of residues in

carcasses. Dansk Veterinaertidsskrift 73(17):911-916.

[ix] Kluge-Berge, S. 1989. Monitoring for contaminants in carcasses

as contaminated with heavy metals, organochlorine compounds,

organophosphorous compounds, antimicrobial agents, growth

stimulants. Norsk. Veterinaertidsskrift 101(1):30.

[x] Prusiner, S.B. 1996. Molecular biology and pathogenesis of prion

diseases. TIBS 21:482-487.

Riek, R., Horneman, S., Wider, G., Billeter, M., Glockshuber, R.,

Wuthrich, K. 1996. NMR structure of the mouse prion protein domain

PrP(121-231). Nature.382:180-182.

[xi] Editorial. 1990. Prion disease spongiform encephalopathies

unveiled. Lancet. 336:21-22.

[xii] Will, R.G. and Mathews, W.B. 1984. A retrospective study of

Creutzfeldt-Jacob disease in England and Wales 1970-79. I. Clinical

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[xiii] Masood, E. 1996. `Mad cow' scare threatens political link

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[xiv] Butler, D. 1996. Slow release of data adds to BSE confusion.

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[xv] Klaffke, O. 1996. Swiss cull to meet fears of BSE. Nature.

383:289.

[xvi] Smith, P.G., Cousens, S.N. 1996. Is The new variant of

Creutzfeldt-Jacob Disease from Mad cows? Science 273:748.

[xvii] Lasmezas, C.I., Deslys, J.P., Demalmay, R., Adjou, K.T.,

Lamoury, F. Dormont, D., Robain, O., Ironside, J., Hauw, J.J. 1996.

BSE transmission to macaques. Nature. 381:743-744.

Aguzzi, A. 1996. Between cows and monkeys. Nature. 381:734-735.

[xviii] Skegg, D.C.G. 1996. Sacred cows, science and uncertainties.

Nature. 382:755-756.

Masood, E. 1996. BSE transmission data pose dilemma for UK

scientists. Nature. 382:483.

Wise, J. 1996. Scientists find low level transmission of BSE. BMJ

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[xix] Kluger, J. 1997. Could mad-cow disease spread further? Time.

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[xx] Butler, D. 1996. Statistics suggest BSE now `Europe-wide'.

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[xxi] Tricker, A.R. and R. Preussmann. 1990. Chemical food

contamination in the initiation of cancer. Proc. Of the Nutritional

Society 49: 133-144.

[xxii] Holmberg, S.D., Osterholm, M.T., Senger, K.A., Cohen, M.L.

1984. Drug-resistant Salmonella from animals fed antimicrobials. New

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Page updated 10/15/2004

JoAnn Guest

mrsjo-

DietaryTi-

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AIM Barleygreen

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