Background

Antibiotics were developed in the 1940s to treat bacterial infections in humans and animals.

Following the rapid development of intensive pig farming systems in Europe/Ireland from the 1960s, the levels of infectious diseases on farms, both bacterial and viral, that needed to be controlled, increased. Throughout the 1970s and 1980s, antibiotics, particularly in feeds, were not only used to treat pigs but also to prevent them developing diseases and to promote their growth.

The use of antibiotics as growth promoters was banned in the EU in 2006.

In the late 1990s, the Dept of Agriculture commenced an enhanced sampling/testing programme of pigs at slaughter for residues of antibiotics (more than 55,000 samples annually). At the time, there were concerns that pig herd owners were not adhering to the required withdrawal periods following the administration of antibiotics to pigs, prior to sending them for slaughter.

Laboratory test results confirmed that ‘there were problems’ with antibiotic residues in pig meat from a small number of farms. The finding of antibiotics in a pig carcass resulted in the ‘supplier herd’ being placed on ‘a blacklist’ and flagged for increased testing for antibiotics for the next two months. The cost of such testing was borne by the herd owner.

The testing programme, the improved enforcement of veterinary medicines legislation together with advice/information given by the veterinary practitioners helped make farmers more aware of the necessity to adhere to the correct periods of withdrawal after the administration of antibiotics.

In recent years, Ireland's Department of Agriculture, Food and the Marine (DAFM) is satisfied that the results of the sampling programme carried out annually under the National Residue Plan reflect the fact that farmers are very careful in adhering to the correct withdrawal periods prior to presenting pigs which received medicines, for slaughter. Since 2009, the number pig meat samples which tested positive for antibiotics has been very low, ranging from zero to three pigs per year out of a total of almost three million pigs slaughtered.

So is there still a problem with misuse of antibiotics in pigs since the findings of residues in pig meat is ‘almost historic’? What is the issue?

Antimicrobial/antibiotic Resistance (AMR)

Antibiotics are no longer 100 per cent effective in the treatment of some bacterial diseases in both humans and animals, with particular strains within families of bacteria developing a complete resistance to treatment with certain antibiotics. Antibiotics can be divided into a number of ‘major families’ e.g. tetracyclines, Β-lactams/penicillins, sulphonamides, quinolones, cephalosporins, etc.

Why, as pig farmers should you be concerned about AMR? Is the over-prescribing of antibiotics by the medical profession not the main causative factor in the development of AMR?

The reality is that any kind of antibiotic use in people or animals can promote the development and spread of AMR. Moreover, the misuse of antibiotics in food animals has important consequences for public health, as it promotes the growth of antibiotic-resistant bacteria and resistant genes that can be passed on to people. Some bacteria e.g. Salmonella, E. coli, staphlococci, that cause diseases in pigs can also be infectious to humans and are classed as ‘zoonotic bacteria’.

Strains of these zoonotic bacteria e.g. Salmonella typhimurium (DT)104 are known to have developed multi-resistance. Some antibiotics are classed as critically important for human medicine e.g. the quinolones (similar to Marbocyl, Baytril) and cephalosporins. Should resistance develop to these medicines, as is the case, then we are looking at treatment failures.

Tackling AMR is a public health priority. Experts in human and animal health have come together under the auspices of the WHO, OIE (Animal health), Food and Agriculture Organisation of the UN (FAO), Codex Alimentarius Commission and the European Commission, to tackle AMR from a food safety perspective. AMR infections in humans, in the European Union region, are known to contribute annually to more than 25,000 deaths, four million patients acquiring health care associated infection and costs of €1.4 billion in lost productivity and healthcare.

Need for Urgent Action

The EC has developed an action plan to tackle AB resistance. This multifaceted approach involves effective coordination of actions and an exchange of information among agricultural, food, veterinary and health sectors. A number of action points relevant to the food animal sector include:

• Improving awareness on the appropriate use of antimicrobials
• Strengthen EU law on veterinary medicines and medicated feed
• Have recommendations on prudent use of antibiotics
• Strengthen surveillance systems on AMR and antimicrobial consumption in animal medicines.

In Ireland, there are currently expert groups working on an inter sectoral national strategy and action plan on AMR. It is expected that targets will be set to reduce the use of antibiotics in food animals, with a particular focus on use in feed in the pig industry.

Irish Pig Industry and the Use of Antibacterials in 2013

What is the attitude of the commercial pig farmer to the use of antibiotics in all forms, i.e. injectables, oral powders/water and most critically, in feedingstuffs? Is there a danger that a level of complacency exists since the tackling of the problem of antibiotic residues in pig meat has been largely successful? Is there a perception that the industry does not have a problem with antibiotic usage or misuse?

The prevalence of AMR organisms in pig herds is not as easy to quantify as the testing for antibiotic residues in carcasses. The results of research work done in recent years in this field in Ireland cannot be ignored.

Does Ireland as a country have data regarding the use of antibiotics in food animals, and moreover on a species basis? The truth is we do not have such definitive data. Currently, the Irish Medicines Board (IMB) collates information regarding usage as part of a Europe-wide surveillance.

Recent information indicates that approximately 100 tonnes of antibiotics 'are used across all food producing species' annually in Ireland, of which 40 per cent+ relates to usage in the pig industry.

How does usage on Irish pig farms compare with that in other EU States e.g. Denmark, Netherlands? Currently, there are insufficient data available in Ireland to make an accurate comparison. However, data available regarding the production of medicated feedingstuffs at feed mills and also home-mixed on farms indicates that the level of antibiotic usage on a small percentage of pig farms is high.

In October 2012, there were 1,700 active pig herds, having approximately 1.35 million pigs; 40,000 breeding pigs and 1.21 million fatteners. Only 18.5 per cent of herds had more than 500 pigs and only 1.5 per cent of herds had more than 10,000 pigs. The latter category (26 herds) accounts for around 30 per cent of the total pig population.

What information does DAFM have on the usage of antibiotics in the pig industry? It inspects and licenses compound feed mills and a number of pig farms (around 40 home-mixers) to manufacture medicated pig feed. The use of medicated feed is prescribed and directed by specialist veterinary consultants.

DAFM is aware of the pattern of usage of antibiotics in the various pig diets, from creep, through link, weaner and early fatteners. DAFM has actively engaged with the specialist vets and individual producers advising the more targeted usage of medicines, particularly in the feed.

Factors Influencing a High Usage of Antibiotics - Mostly in Feed - on Some Commercial Pig Farms

The answer lies in the presence of viral diseases like PRRS, circovirus (wasting; PCV) with secondary bacterial infections - respiratory or enteric (i.e. gut-related).

Vaccination programmes against the former and other viral infections are proving successful but there is a reluctance on the part of some herd-owners to request a specialist veterinarian to carry out investigative work, herd health assessment, post-mortems and laboratory tests to determine if ongoing antibiotic usage is necessary or could it be more targeted with a view to ceasing the practice in the long term.

The attitude may be that there is no need - or producers are afraid - to change the practice of routine, prophylactic in feed medication if the pigs are ‘doing well’. However AMR is a global problem and the pig industry needs to be seen to be acting responsibly on this issue.

Type of feed mixing and delivery systems: Many of the larger integrated units use a ‘wet feeding system’ that does not have dedicated mixing tanks to service the different age groups of pigs. At worst, one mixing tank may mix and feed sows and weaners. In such cases, if a vet were to prescribe medicated feed for the first-stage weaners, there is the risk of a residue of antibiotics carrying over into the second stage and sow diets, with the possibility of encouraging the development of AMR bacteria in the latter groups.

Many in-feed medications are licensed for the treatment of conditions like pneumonia for periods from seven to 14 days. However, many pig farms have satellite wet mixing tanks that service a group of weaners for a four- or five-week cycle. With such a system, it is difficult to target the treatment of a small group of pigs, e.g. for one week post weaning, if all first-stage weaners are on the same feed delivery line.

Whether a herd owner is purchasing or home-mixing medicated feed, there is no doubt that this method of feeding would have to be adapted to ensure that only a small number of target groups receive medication.

Water medication is a good solution to the problem outlined above and both the Dutch and Danish pig industries have embraced this alternative to in-feed medication. However, there are some practical difficulties associated with water medication, especially in wet feeding systems. The availability of water-soluble antibiotics is less than those licensed for use in feed. Herd-owners perceive the cost of the former to be high. However, there is no doubt that the use of water medication has to be considered as it would allow a much more targeted delivery of medication than is currently possible with some feeding systems..

Who decides that medicated feed is required for weaners month after month? Is it primarily the farmer or a veterinarian? What role does the feed compounder play in making the decision as to which antibiotic is incorporated in the feed? Where a compounder ‘provides the herd owner with a choice of incorporating only two different medicines in a diet’, is there a risk that the farmer may ‘due to custom and practice’ convince himself that a medicine is effective (on both medical and cost grounds)?

Herd owners need to engage with a veterinarian or a nutritionist to evaluate critically the benefit (if any) of continued use of in feed medication in weaners.

Veterinary services to the pig industry: Many pig farms use the services of two or more veterinarians. Which vet prescribes and supplies antibiotics? Does the farmer purchase the bulk of the antibiotics from a vet who is not the primary vet to the pig unit, purely on cost grounds?

Legally, a vet shall not prescribe the use of a medicine for animals unless he or she has visited the farm sufficiently often and recently enough to have an accurate picture of the current health, welfare and disease status of the pigs on that premises.

Do pig herd owners fully understand and appreciate the importance of this statement? The prescribing vet must also know what vaccination programmes are in place, be fully aware what other vets have advised/prescribed and be prepared to change the course of treatment, including the complete cessation of in feed medication, albeit that some farm clients may not accept the latter advice.

Pig herd owners should ideally contract one veterinary practice to draw up a comprehensive herd health programme that aims to prevent infectious diseases by ensuring biosecurity, good production and management conditions together with proper vaccination programmes. The use of antimicrobials in intensive pig farming is unavoidable but their use MUST be justified by science.

Concentration of pigs on one site: There is no doubt that having a system where all stages of production from birth to finishing/slaughter are on a single site contributes to difficulties in breaking the cycle of infection (bacterial or viral). It may not be possible to have any ‘rest time’ between the movement of batches of pigs to allow for proper disinfection of premises. Herd owners, may decide to ‘request a vet’ to prescribe in feed medication for all young pigs post movement ‘as a precaution’. This could not be described as the ‘responsible use’ of antibiotics.

Biosecurity failure: Pig herd owners and the consultant veterinarians shall ensure that all the employees on farms fully appreciate the importance of adhering to a comprehensive documented ‘biosecurity programme’ to prevent the entry and spread of diseases to livestock. Failure to deliver this message on some farms could result in a general acceptance by management that ‘the use of in feed medicines is required to maintain a level of health in pigs’.

Way Forward

The European Commission is drafting guidelines for the prudent use of antimicrobials in veterinary medicine. A number of bodies associated with human and animal health are helping to develop a national policy for Ireland to ensure the prudent use of antibiotics and minimise the misuse in food animals.

Ireland will be setting targets to reduce usage of antibiotics over the next five years. The focus will be on mass/group medication of pigs and poultry initially. France has set a target over a five-year period to reduce the use of antibiotics by 25 per cent, the Dutch have set a target of a 70 per cent reduction by 2015. The Danes are well on the way to achieving a 50 per cent reduction over recent years and are continuing to set the standards.

What can the Irish pig industry expect and what can be achieved?

The primary responsibility for prudent use of antibiotics in the pig industry lies with the small number of prescribers (vets) and the end users.

To achieve the targeted reductions in the use of antibiotics, pig farmers may have to consider implementing multiple changes to their production practices (e.g. improved diet, later weaning, and increased space per pig) together with adapting the feed mixing /delivery systems to permit the targeted delivery of in feed medication.

Farmers should consider having one primary veterinary advisor who has overall responsibility for the care of the animals.

A documented herd health programme is an absolute requirement and regular updating shall take place to include close monitoring of the efficacy of antibiotics being used and also the quantities administered.

The use of antibiotics must be justified by the decision of a veterinarian (scientific), and based on a clinical evaluation of the herd. Where the latter is not possible then diagnosis should be based on past experience, on previous laboratory sensitivity testing and on the epidemiological status of the farm. Consideration should be given to alternative forms of treatment that may be equally efficient.

There should be no pressure on the vet by the farmer to prescribe particular antibiotics. Before commencing treatment, the vet should ascertain that the infection does have a bacterial element. Where possible, laboratory tests should be used to determine the main pathogen and the sensitivity to antibiotics.

The course of antibiotic treatment should be in accordance with the instructions on the product data sheet, or as prescribed by the vet. The person administering a medicine should adhere fully to the dose rate and duration of treatment and should not make changes without consulting the veterinary practitioner. If the vet prescribes a three-day course of treatment, then do as directed.

The prolonged use of in-feed antibiotic medication e.g. three or four weeks (unless permitted by the information on the data sheet for a medicine as authorised by the Irish Medicines Board) is very likely to increase the risk of AMR organisms in the pig herd.

It is important to note that some families of antibiotics, e.g. quinolones (Baytril type) and some cephalosporins, which are critical to successful treatment of certain infections in humans - such as forms of salmonellosis, coliform infections, streptococcal infections - are also being used to treat infections in pigs. Therefore, these medicines should not be included in the first line of defence and their use in pigs should be limited to cases where antibiotic sensitivity tests indicate that their administration is required for effective treatment.

The use of all medicines, including in feed, must be recorded by the herd owner.

Will DAFM follow the example set by Denmark and require the vets, the pharmacists and the end using pig farmer to submit information to a central agency regarding the quantities of antibacterial medicines prescribed, dispensed and administered respectively on a bi annual basis (or more frequently)?

This option is under consideration. Responsible pig producers should see this exercise as something that would be beneficial to promoting the industry. Where necessary, the information acquired would allow the regulating body to take sanction against any one of those parties (farmers or vets) if the quantities of antibiotics being used in a particular herd, deviated greatly from what could be considered prudent use.

Raising awareness

Across the pig industry, there is a need to provide the herd owners, farm managers and pig farm employees in general with the relevant information on AMR and correct use of antibiotic medicines.

How is this best delivered? The primary veterinarian contracted to a pig farm should factor in the education of the end users in the correct usage of medicines as part of any herd health programme.

Pig farmers should welcome such a development. Education programmes for the pig producers should focus on correct treatment and appropriate use of antibiotics.

DAFM has a role to play through its veterinary inspectorate and possibly via an information campaign directed to the intensive farming sectors. The recently formed Irish branch of RUMA (Responsible Use of Medicines in Agriculture Alliance) should consider developing and publishing a sector-based guidance on the responsible use of antibiotics.

Pig meat consumers

The general public needs to be assured that the food derived from animals is produced in a manner with the minimal use of medication. There are moves afoot, by retailers of poultry products in other EU countries to demand of their suppliers that they do not exceed a set limit of usage (mg/kg bodyweight) of antibiotics throughout the lifetime of the bird. This is one of the requirements for membership of their quality assurance schemes and is a pre-requisite to being accepted as a supplier to that food retailer.

The Irish pig industry should be leading the way in setting standards for the production of pork products with the minimal use of antibiotics and should embrace the concept of being able to provide the information to back up any marketing campaigns promoting Irish pig meat.

In conclusion, the message that farmers should understand is that the primary responsibility for the prudent use of antibiotics on Irish pig farms lies with the prescribing veterinarian and the herd owner who administers the products.

Antimicrobial resistance is a global problem and the Irish pig industry has a part to play in helping to solve what is a serious issue for both human and animal health.

December 2013