Antibiotic use in the food-chain

by Professor Joe Lederman , Julian Wan and John Gao © Lawmedia Pty Ltd, August 2007
Australian Food Lawyers & Consultants

In early August 2007, it was revealed in the media that one-third of samples of prawns, fish and other seafood from China, Indonesia, Vietnam and Thailand contained traces of antibiotics (see Concern over antibiotics in seafood). This article seeks to outline some of the issues surrounding the use of antibiotics not just in seafood, but the food chain in general and its possible impact on public health.

Background - Antibiotic use in for food production

In 1999, an Australian government committee report of the Joint Expert Advisory Committee on Antibiotic Resistance (JETACAR) in Australia estimated that, on average, two-thirds of the antibiotics imported into Australia each year were for veterinary use, with the majority of this being added to stock feed.

Antibiotics are used in primary production all over the world in cattle, pork, poultry and seafood. Producers use antibiotics in their animal feeds in order to maintain the health of the food producing animal, to increase feed lot efficiency and as ‘growth promoters’.  Studies have shown however that the economic and productivity gains from using antibiotics in feed for food producing animals is not that great – it has been shown that weight gain from antibiotic use is variable, but at most the gain is approximately 2%: see the article titled The Routine Use of Antibiotics to Promote Animal Growth Does Little to Benefit Protein Undernutrition in the Developing World. In another study reported by Pfizer, also examined in the article referred to previously, antibiotic use did not reduce the mortality rate of chickens, and in Denmark and the United States where antibiotic use in poultry was stopped, no significant change in the mortality rate was observed. It should be noted however, in developing countries antibiotic use may result in significantly higher benefits, with the authors of the abovementioned article identifying one study in India which found that poultry experienced a 9% increase in weight as a result of the antibiotics – the final weight of the chickens in this study was however only half the weight of chickens bred in developed countries without antibiotic use.

Given these studies, prima facie it would appear that the widespread, indiscriminate use of antibiotics in food production in developed countries may-be less necessary (in relation to the weight gain issue) than previously thought and, in fact, antibiotic usage is being reduced or even prohibited in many of the developed countries. Comparing the weight of the poultry mentioned above between India and developed countries suggests that factors such as farming practices, environment, feed quality and quantity have a much greater impact on the weight gained by animals than antibiotic use.

Regulation of antibiotic use in Australia

There are two areas of regulation when discussing antibiotics and food – regulations which deal with antibiotic use in animal feed while the animal in question is still being reared and regulations which govern antibiotic content in a food.

The amount of antibiotics which may be present in a food is governed by Standard 1.4.2 of the Australia New Zealand Food Standards Code (“the Code”).  Standard 1.4.2 sets the Maximum Residue Limits (“MRLs”) which is the maximum permissible residue limit for agricultural and veterinary chemicals which is allowed to be present in a food. Clause 2 of Standard 1.4.2 requires that unless a permitted MRL for a chemical is listed in Schedule 1, the chemical must not be detectable in the food, and where there is a prescribed MRL, that the residue present is below what is allowed in the Schedule.  For example, the antibiotic Virginiamycin may be present in cattle meat, poultry and sheep meat (amongst others) at a level of 0.1 mg/kg. In comparison neither fluoroquinolones or quinolone, both considered ‘next-generation’ antibiotics, are listed in Schedule 1 to Standard 1.4.2, meaning food must be completely free of these antibiotics. The imported seafood which had been identified by the Australian Quarantine and Inspection Service as containing fluoroquinolones and/or quinolone (see Concern over antibiotics in seafood) were therefore clearly in breach of the Code and could not have been legally sold to consumers in Australia.

The other area of Australian law which regulates the use to antibiotics in the food supply chain is the Commonwealth Agricultural and Veterinary Chemicals Code Act 1994 (“Agvet Act”) and the ‘Control of Use’ legislation in each State and Territory. The Commonwealth Agvet Act controls all aspects of agricultural and veterinary chemicals up to the point of retail sale, while State and Territory laws deal with the chemicals following their point of sale.

Veterinary chemical product is defined in Section 5 of the Agvet Act as “a substance or mixture of substances that is represented as being suitable for, or is manufactured, supplied or used for, administration or application to an animal by any means, or consumption by an animal, as a way of directly  or indirectly:

(a) Preventing, diagnosing, curing or alleviating a disease or condition in the animal or an infestation of the animal by a pest; or

(b) Curing or alleviating an injury suffered by the animal; or

(c) Modifying the physiology of the animal:

(i) So as to alter its natural development, productivity, quality or reproductive capacity; or

(ii) So as to make it more manageable; or

(d) Modifying the effect of another veterinary chemical product.”

The definition of “animal” is also very wide, and includes any animal other than a human being, whether they are food producing or not and expressly includes fish and crustaceans. The definition of Veterinary Chemical Product therefore clearly covers the use of antibiotics in agriculture and aquaculture for both usages, name the treatment of disease in a food producing animal or fish and as a growth promotant.

As a Veterinary Chemical Product, an antibiotic which is intended for use in food producing animals  must first be reviewed and registered under the Agvet Act by the Australian Pesticides and Veterinary Medicines Authority (“APVMA”) (note there are exceptions in the definition of  Veterinary Chemical Products for products substances prepared by a pharmacist or  veterinary surgeon for the use in their profession).

Under Section 74 of the Agvet Act, it is a criminal offence for a person, at any time, to have in their possession or custody with the intention of supply a substance that is likely to be used as an active constituent for a chemical product unless the substance has been approved (or exempted) by the APVMA or the possession of the substance has been authorised by a permit. The offence of supplying an unapproved active constituent is found in Section 76 of the Agvet Act.

Similarly it is illegal for a person to have in their possession or custody, or to supply a Veterinary Chemical Product that is not registered unless that product has been exempted by the APVMA or possession is authorised by a permit (see Section 75 and Section 78 of the AgVet Act).

Even where an active constituent or Veterinary Chemical Product has been approved or registered, it must only be supplied on the conditions that it has been approved for – see Sections 77 and 79 of the AgVet Act.

The Approval and registration of Veterinary Chemical Products is governed by Part 2 of the AgVet Act. When assessing an application for registration of a chemical, if it is likely that the chemical product would be present in foods at a level which is not already permitted under Standard 1.4.2 Maximum Residue Limits (as discussed above), the APVMA must notify Food Standards Australia New Zealand of the application under Section 13A of the Agvet Act.

While the AgVet Act provides uniform regulation of the registration and supply of antibiotics in Australia, by virtue of its adoption by the States and Territories (for example, such as by the Agricultural and Veterinary Chemicals (Victoria) Act 1994), there is no uniform Control of Use legislation in Australia. While the legislation in each State and Territory makes it an offence to use an unregistered Veterinary Chemical Product, the exemptions which each jurisdiction may provide (either through the issue of permits or other regulations), means there is no guarantee that a primary producer who is able to utilise a particular veterinary chemical product in one jurisdiction will necessarily be able to use the same product in another Australian jurisdiction under the same conditions, or to use the product at all (for example Section 6 of the Agricultural and Veterinary Chemicals (Control of Use) Act (Vic) 1992, and Section 12e of the Chemical Usage (Agricultural and Veterinary) Control act (Qld) 1988).

Antibiotics in the food chain and antibiotic resistant bacteria

The Maximum Residue Limits imposed on food ensure that food which contains trace amounts of antibiotics are still safe for consumption, and where trace amounts of antibiotics are not safe then consumers are protected. The safety of food is only part of the safety equation when examining the issue of antibiotics in the food chain.

With the use of any antibiotic, it is only a matter of time before bacteria evolve and become resistant. The question this raises is whether by feeding animals the same antibiotics which are used to treat life threatening bacterial conditions in humans puts people at risk by increasing the likelihood of antibiotic resistant bacteria evolving.

Antibacterial resistance occurs in two distinct stages (see Page 17 The use of antibiotics in food-producing animals: antibiotic-resistant bacteria in animals and humans (“JETACAR Report”)):

  1. Genetic Change – Bacteria can become resistant to an antibiotic either by mutation of the bacteria, or because an existing antibiotic-resistance gene has been transferred into the bacteria from another resistant bacteria;
  2. Selection – once a bacterium is resistant (either due to mutation or transfer of resistance gene), the bacterium will continue to grow in numbers despite the presence of antibiotics. The amount of antibiotics used serves as a general indicator of selection pressure – the more exposure there is to an antibiotic, the stronger the pressure is for resistant bacteria to grow and multiply in numbers.

The use of antibiotics in the food chain can therefore impact on the development of antibiotic resistant bacteria a variety of ways, for example if an animal is fed antibiotics, and the resulting food from that animal contains residual levels of that antibiotic, bacteria which affects humans will effectively be exposed to higher levels of antibiotics. The increased exposure of animals to antibiotics also means animal bacteria are more likely to develop antibiotic resistance which means there is a larger pool of antibiotic resistant bacteria from which a resistance gene could be transferred to bacteria which has an effect on humans.

From  examination of research reports, the JETACAR Report was able to draw the following conclusions, amongst others, to answer the following questions:

  1. Does giving antibiotics to animals result in the emergence of antibiotic resistant bacteria? Yes. It is universal experience that resistance will emerge whenever antibiotics are used. – See page 48, JETACAR Report.
  2. Do resistance genes from animal bacteria transfer to human pathogens? Yes. There have already been examples of resistance gene transfer between animal and human bacteria. Even though the frequency of this was uncertain, JETACAR stated that frequent gene transfer is not necessary to cause resistance in the human population, as antibiotic use would work to amplify the level of resistance – see page 55, JETACAR Report.
  3. Do antibiotic resistant bacteria from animals cause disease in humans? Yes. Listing antibiotic salmonella as an example, JETACAR stated that there is already “ample evidence” that antibiotic-resistant strains of animal bacteria can cause disease in humans – See page 56 JETACAR Report.

Health Risk Extends Beyond Food Safety Risk

The conclusions drawn by JETACAR show that the use of antibiotics in the food chain poses a safety risk beyond the issue of just food safety: Food which is produced from an animal which has been fed antibiotics can be perfectly safe and free of antibiotic residue, BUT the fact that antibiotics were used in the food’s production creates a potential risk to public health by expediting the evolution of antibiotic resistant bacteria in animals and humans.

The fact that our current food law (in the form of Maximum Residue Limits being prescribed in the Australia New Zealand Food Standards Code) will minimise the exposure of humans to increased levels of antibiotics through food will NOT reduce the wider adverse health impact of feeding antibiotics to animals especially animals in countries outside Australia.

Recent studies have suggested that Australia’s policy of restricting antibiotic use, such as fluoroquinolones in food production may be responsible for the lower levels of antibiotic resistant bacteria found in the Australian population:  see Less antibiotic use in food animals leads to less drug resistance in people, study shows. Nevertheless, it must be remembered that even if a food contains no trace of antibiotics, the animal may have been exposed to considerable quantities of antibiotics and thus aided the evolution  of antibiotic resistant bacteria anyway.

Need for international action, Australia cannot solve the problem in isolation

It must also be borne in mind that the world is now truly a global community, and while Australia’s policy on antibiotics in food production have had some beneficial impact on discouraging the development of resistant bacteria amongst the Australian population, Australia is not safe from the problem unless the rest of the world also tackles the issue. Even if Australia was to ban all antibiotic use in food producing animals for the Australian food supplyand prevent the importation of all foods containing any traces of antibiotics, it is still possible for resistant bacteria to develop in another country where antibiotics are more widely used and for those resistant bacterium to infect the Australian population as a result of human movement across international borders.  In other words, the solution must include the restriction of antibiotic usage for animals outside Australia and not just inside Australia. While each country may be able to reduce the public health consequences, only a co-ordinated international approach will truly tackle the health risk problem for Australians as well as others.

This is general information rather than legal advice and is current as of 12 Dec 2015. We therefore recommend you seek legal advice for your particular circumstances if you want to rely on advice or information to be a basis for any commercial decision-making by you or your business.