The Use and Misuse of Antibiotics in UK Agriculture - part 3
Residues of Dangerous Drugs in Intensively Produced Chicken Meat and Eggs.
Full Report - 
Overview
This report examines the intensive poultry industry and the residues of dangerous drugs that find their way into chicken meat and eggs.
It reveals that because of intensive farming methods, and inadequate consumer protection by the
Ministry of Agriculture, Fisheries and Food (MAFF) and the Food Standards Agency (FSA), Britishfarming may be incubating yet another serious threat to human health in the form of cancers, birthdeformities, drug cross-reactions, and heart failure. This problem however is not uniquely British. Frozen poultry is a globally-traded commodity.
This new threat concerns chemical drugs used to control single-celled protozoan parasites. The
most significant of these is called ‘coccidia’. This causes serious illness in chickens. The drugs are
known as antimicrobials, rather than antibiotics. As with BSE, and so many other food safety
problems, it has its roots in intensive farming methods. In this case, the specific problems are the
unnatural feeding practices and unsanitary, overcrowded, moist, dark, confined conditions in which large numbers of chickens are kept–conditions under which most would undoubtedly perish without drugs to keep them alive until slaughter.
In the past, a number of relatively safe drugs were available to control coccidiosis, but excessive
reliance on drugs rather than good animal husbandry has honed drug resistance and these have
become ineffective on most poultry farms. As a result, the industry now relies on about a dozen drugs,which it uses in rotation to slow the development of resistant strains. Most of these are so toxic they could never be used in human medicine, but the effect of their residues in our food has never been scientifically evaluated.
Almost half of these drugs belong to one family, the ionophores. Warnings of the serious danger
posed by ionophore food residues come from the deaths of horses from eating pig feed, turkeys fromeating chicken feed containing recommended levels, dogs and cats from eating pet food containingresidues, and cattle and sheep from eating residues in their food. Chickens have been accidentallyparalysed by overdosing their feed. Other licensed antimicrobials may cause cancer and birth defects but scientists disagree and the truth cannot be established because the necessary scientific trials have never been undertaken.
British consumers now eat more chicken and chicken products than ever before. On average we
consume a third of our body weight in chicken each year. Chicken is cheap and available, but as ourconsumption of chicken has gone up so has the use of these toxic drugs. As a result, assumptionsmade in the past about their safety as contaminants in our food should be revisited. Everyone knowsthat intensive chicken is produced at a high cost to the welfare of the birds, but do poor welfare conditions also have implications for our own health?
Driven by consumer concerns and pressure from multiple retailers, there has been an effort to
improve the poor image of the British broiler poultry industry in recent years. Some 85 per cent ofproduction, it is claimed, is now linked to the ‘Assured Poultry Production’ scheme, where it is
maintained that significant improvements have been made. The limited evidence available suggests things have improved far less than the industry would like us to believe. However, even in the show piece units where recommended practice is followed fully, there remains an intrinsic welfare problem in all broiler houses. Many commentators have drawn the link between this and some of the obvious signs of ill health in birds, such as lameness and blisters. This report suggests there is also a link with the less visible diseases that are normally controlled by the routine inclusion of drugs in feed. Residues of these drugs turn up in chicken liver and eggs on a regular basis. They are also present in chicken flesh.
Main Findings
This report finds that:
1 Until 1998 there had been no statutory testing for drug residues in poultry in the UK.
The scale of the residue problem that has since emerged should alert us to a range of
issues relating to food safety regulation, farming practices and consumer choice.
2 Government regulators have routinely provided misleading information in their public
statements about the incidence of drug residues in chicken meat and eggs.
3 They maintain that 99 per cent of poultry meat and 97 per cent of eggs are free of
detectable residues. However, detailed analysis of the data on which their summaries are
based suggests the actual levels could be up to 2,000 per cent higher.
4 Nicarbazin, shown to cause birth defects and hormonal problems in animal studies, has
never been carefully evaluated for safety in humans. In 1999, the last year for which full
figures are available, 17.8 per cent of chicken livers tested had residues of nicarbazin in
excess of the Maximum Residue Limit of 200 micrograms per kg., the highest being
10,500 micrograms per kg., over fifty times the legally permitted level. Since then 127
out of 700 (18 per cent) of tested chicken livers contained residues of nicarbazin. Studies
show that where it is present in liver it will also be found in flesh at lower levels. In
addition it is found in approximately 2 per cent of eggs.
5 Lasalocid is not licensed for laying hens. It is a member of the potent cardio-toxic
ionophore family of drugs that have never been properly evaluated as residues in food.
No Maximum Residue Limit has been set. Yet in 1999, one in every dozen tested egg
samples (8.5 per cent) contained residues of lasalocid above the arbitrarily-decided
action level of 100 micrograms per kg. The highest of these was 5,400 micrograms per
kg. 12 per cent of chicken muscle also tested positive. Most recent results suggest that
half of all quail eggs and 30 per cent of all quail muscle on sale in the UK contains
residues of lasalocid above 100 micrograms per kg.
6 Dimetridazole (DMZ) has never been properly evaluated for safety. Scientific committees
disagree about its safety, but it is suspected of being able to induce both cancer and birth
defects. It is also not licensed for laying hens or broilers, yet in 2000, 2.6 per cent of
broiler feed tested contained DMZ, no tests were undertaken for laying hens but in 1998,
2 per cent, and in 1999, 0.5 per cent of eggs contained residues of DMZ.
7 The misleading nature of official government statements on drug residues in food are
the result of statistical and presentational techniques used by the Veterinary Medicines
Directorate (VMD) an executive agency of MAFF. Essentially residues have been
expressed as a percentage of all tests for all substances in chicken meat and eggs (most of
which are negative) rather than as a percentage of the tests for each individual drug
residue. As a result, the general public has been given an entirely false account of the
true level of drug residues in food.
8 British consumers eat almost 10 billion eggs each year, and so even contamination in a
tiny fraction of one per cent of eggs suggests a very large number of contaminated eggs
are being eaten each day, and a large number of individual consumers potentially put at
risk. Despite this, just 525 samples of eggs are tested each year by government regulators
– one test for every 18 million eggs consumed. Samples for individual drugs in eggs
from different species (hen, quail etc.) in different production systems (battery, perchery,
free-range, organic) can be very small and insufficient to reflect the national picture or
reveal patterns between different production systems.
9 Ionophore drugs can react badly with some prescription medicines, yet doctors have not
been notified of the possible presence of dietary ionophore residues and are therefore
unable to take this into account when prescribing.
Discussion
m In 1999 (the last year for which full figures are available) a total of 8,063 poultry samples
were tested for all likely drugs and contaminants. Of these, 8.007 (99.3per cent) were, as
the VMD states, ‘free of detectable residues’. However, only 264 samples of poultry liver
were tested for nicarbazin, of which 47 (17.8per cent) contained residues above the MRL.
This same statistical trick, of expressing residues of each drug as a total of all tests
undertaken for all substances, rather than as a percentage of the tests for that drug, is used
throughout the residue-testing programme for each of the drugs of concern, and is a false
basis on which to found policy on antimicrobials. It may even give the poultry industry itself
the impression that there is no real problem.
m The actual situation may be worse even than these figures suggest. There are indications
that when residues are found, the VMD warns the producer and suspends testing while
attempts are made to find out what went wrong. The group set up by the VMD to reduce
residues of nicarbazin is the ‘VMD/Industry Initiative’. This entity is highly secretive. The
VMD will not even disclose how many members it has, let alone who they are or what
reports have been generated.
The VMD also maintains that these residue problems are caused entirely by ‘contamination
at the feedmills’. This has clearly contributed to the problem, especially with eggs (in 1998
an organic egg was found to contain low residues of nicarbazin). However, while the VMD
maintains that the residue problems can be solved by technical improvements at mills and
an industry education campaign, evidence suggests otherwise. Despite regulatory effort
residues of lasalocid in eggs rose sharply in 1999. In addition to the problem at mills
residues in both chicken meat and eggs result from many other factors. These include:
- Accidental mixing up of different batches of differently medicated feed
- Failure to empty bins completely before refilling, and failure to clean bins and
automatic feeding equipment properly
- The setting of inappropriately short withdrawal times for some drugs
- The failure of some producers (either for financial reasons, or through concerns
that disease will reappear) to observe drug withdrawal times fully, before sending
birds to slaughter
- The use of very high stocking levels and the associated practice of ‘thinning out’
some birds towards the end of a production cycle when space is most limited
- The inevitable recycling of drug residues after medications are withdrawn as
chickens peck their own excreta – something they cannot avoid in broiler systems
- The dropping in 1998, of the requirement that veterinarians must consider and
list all antimicrobials included in feed, when prescribing veterinary medicines for
simultaneous use. (Some veterinary drugs dramatically reduce the elimination of
ionophores from the body of farm animals. In some situations this could account
for residues still being present in birds at slaughter.)
When eggs are tested a ‘sample’ is made up of a dozen eggs, which are broken and
mixed before testing. But about 90 per cent of egg samples show no detectable residues,
so this pooling of eggs has the potential to dilute the actual residue levels in individual
eggs considerably and could reduce levels of some samples below detection limits. The
VMD maintains this is not significant, since all eggs from individual suppliers will carry
similar levels of residues. If this is true, however, it suggests that the total number of eggs
actually contaminated could be significantly higher than official results indicate, since
there is no information on the proportion of eggs released on the market by producers
whose samples turn out to be positive.
Government also maintains that residues of these drugs pose no health risk. It claims,
for example, that ‘Nicarbazin residues are not primarily a safety issue’. However, the
former Department of Health’s senior toxicologist, Dr. Derek Renshaw, now with the
Food Standards Agency, is known to be personally concerned that nicarbazin was never
properly evaluated for mutagenicity. He has stated in a personal communication seen by
the Soil Association: ‘I feel very uncomfortable when asked to comment on the consumer
health significance of any residues of nicarbazin found in foods.’
The same picture emerges for several other drugs. Dimetridazole (DMZ) is banned
throughout Europe, except in the UK, where it can be used only for turkeys, pheasants,
other game birds and pigeons. Yet residues are found in chicken feed and as a result in
eggs. EU Committees disagree about the dangers posed by DMZ. One, the CVMP,
recognises that DMZ may be genotoxic and carcinogenic and that guidelines governing
its use currently do not offer adequate safety guarantees. Another, SCAN, believes that
the weight of evidence indicates that DMZ should not be considered as a genotoxic
compound in mammals. However, Germany wants to see DMZ banned entirely, and
British toxicologists (Dr. Derek Renshaw and Professor Diana Anderson) state: ‘We are
concerned that dimetridazole may be genotoxic. The dimetridazole molecule contains a
structural alert: the 5-nitro ring. Several other compounds with a 5-nitro ring have been
convincingly shown to be genotoxic.’
Another large family of drugs, the ionophores, is also used to control coccidiosis in
poultry. Some ionophore drugs are currently included in chicken feed at up to half the
lethal dose. Susceptibility to the drugs varies greatly between species, individual animals
and between different ionophores. Given the size of the industry and its cut-throat
competitive nature it is hardly surprising that the ionophore drugs sometimes get mixed
up or used at the wrong dose.
Every Christmas for the last several years, large numbers of turkeys have died from
accidental poisoning with the wrong ionophore in their feed, yet no turkeys have been
withdrawn from the market and (as far as the authors of this report have been able to
establish) no monitoring is undertaken to check whether otherwise unexplained heart
attacks in humans may be linked to residues of ionophores consumed in poultry
products.
Yet, the assumption of safety by officials is possible only because there are no studies
evaluating toxicity in humans. Laboratory tests have, however, shown that the ionophore
lasalocid has a strong effect on human heart muscle at low levels and monensin, another
routinely used ionophore, has been found to have a similar cardio-vascular effect in dogs
at levels as low as one millionth of a gram per kilogram. Many of the animals that have
died from ionophore poisoning have died from heart failure.
Extrapolating from the toxicological data in animal tests it seems reasonable to suggest
that some groups within society and some individuals could be significantly more
sensitive to the harmful effects of ionophore residues than others. They could be a
particular danger to older people – and according to the National Food Survey, people
aged 65 – 74 eat more eggs than any other group.
The tragic aspect of this potential problem is that those at greatest risk are also likely to
be the poorest members of society. They have the greatest incentive to buy the cheapest
food available – and this may once again be putting their health, and even their lives, at
greatest risk. Further the poultry industry, as it exists, is currently locked into a vicious cycle, with limited potential for restructuring.
Restructuring the poultry industry
Poultry production has long been a fiercely competitive business; economies of scale and
new techniques mean everything. This competition now takes place at a global, rather
than a national let alone local level. Pressure is intensifying rather than declining as
supermarkets squeeze margins. Chickens were the first species to be bent to the rigors of
the production line, but now when producers anywhere on the planet find a new way of
increasing efficiency in the chicken factory, most producers worldwide have little
alternative but to follow suit. If they do not, within weeks they find themselves being
undercut by others and the tiny profit per bird on which they rely becomes a loss. As a
result most of the smaller producers have already gone.
British poultry producers find themselves in a particularly difficult situation. Pushed by
consumer concerns over welfare and food safety, most UK producers have accepted the
need for a line to be drawn, beyond which stocking densities and other abuses cannot
go. In general, standards on British poultry farms are among the best in the world, yet
the conditions under which the birds are kept is still lower than most of us find
acceptable, and implementation of the guidelines is merely voluntary. With tight margins
it is tempting for some producers to cross that line, either occasionally or regularly.
Stronger controls are placed on the use of drugs within the EU than in many other
countries. An inspection by EU officials in one non-EU country from which we import
poultry found that veterinary drugs are widely available without proper veterinary
supervision. Also between 1997 and 1999 the three antibiotic growth promoters most
widely used in chicken production: avoparcin, virginiamycin and zinc bacitracin were
banned in the EU. Led by some supermarkets and one of Britain’s largest chicken
producers, Grampian, many producers have also now stopped using the two remaining
licensed chicken antibiotic growth promoters, avilamycin and bambermycin.
For society these have been important developments. As the Soil Association has shown
in previous reports, the use of these drugs causes antibiotic resistance and in the case of
both avoparcin and virginiamycin there is compelling evidence that the routine inclusion
of these antibiotics in animal feed was the principal factor behind the development of
new strains of two hospital superbugs.
Yet, the use of these drugs in intensive conditions helped to control disease, make
animals grow more quickly and increase the efficiency of feed conversion. They are still
permitted in many non-EU countries and this helps to keep their production costs as low
as 39 pence per kilo, compared with 49 pence per kilo in the UK. As a result, imports
have risen dramatically over the last two years and now account for over 40 per cent of
all chicken sold in the Britain. It is not hard to sympathise with the chicken producer
who complains that he has been put at a commercial disadvantage while the public
health problem has still not been fully addressed.
Profit margins in the UK are between 7 and 20 pence per bird. Just changing to vaccines
instead of antimicrobials would increase costs by 6.8 pence a bird. Yet consumers would
surely be prepared to pay 7p per chicken more for the added safety it would bring but in
the current world market place and with the rules of the World Trade Organisation as
they are, it is not easy to suggest exactly how this might be brought about.
Organic production offers an attractive alternative for increasing numbers of producers,
but it is clearly unlikely to be the first choice for most of the largest producers with the
heaviest capital investment in poultry houses and automated equipment.
Recommendations
1 In future, summaries of drug residue testing should state honestly and openly the
percentage of positive tests for each drug. An estimate should then be included of how
representative such sampling was for the entire industry. Overall analysis should draw
together data for all available schemes. Efforts should also be made to simplify the
arrangement of tables in residue reports in order to set out in one section data for
individual drugs tested under the statutory, non–statutory and other schemes in order to
permit more meaningful understanding of the overall national picture for each drug
where positive results are found.
2 The drugs lasalocid and dimetridazole should be suspended for use in food producing
animals as a matter of urgency. While better regulation might reduce the incidence of
their residues and metabolites in food, it will never stop this completely and consumers
will have no assurances that potentially dangerous levels of either drug will not turn up
in individual samples of chicken meat and eggs from time to time.
3 The drug nicarbazin should be suspended for use in food producing animals pending
the completion of further studies and thorough consideration by regulatory committees
of its safety as a food residue.
4 The use of all ionophore antimicrobial drugs should be phased out as soon as possible in
place of better systems (such as organic production) where possible, and of vaccination
where not.
5 To make this possible consumers should be prepared to pay extra for poultry produced
in this way. An initiative is needed to bring together consumer group representatives,
multiple-retailers and the poultry industry to consider ways in which this might be
achieved. Multiple retailers should avoid selling chicken as a ‘lost-leader’.
6 Government should ensure that the issues surrounding intensive poultry production,
including the residues of potentially dangerous drugs in chicken meat and eggs, are
included in the fundamental review of agriculture already promised.
7 Government should re-examine the terms of reference of the Veterinary Medicines
Directorate, its sources of funding, potential conflicts of interest, and also consider
handing responsibility for residue testing to the Food Standards Agency.
8 Government should work with our EU partners towards ensuring that poultry imports
match, in every respect, the requirements of EU legislation. Consideration should be
given to including the testing of imported poultry products in the statutory scheme.
l Organic production offers an attractive alternative for increasing numbers of producers,
but it is clearly unlikely to be the first choice for most of the largest producers with the
heaviest capital investment in poultry houses and automated equipment.
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