Expert opinion

Antibiotic use in pigs – an update

Progress regarding reduction in use is starting to happen even before what health expert David Burch considers ‘the over-restrictive proposed EU legislation’ is finalised for veterinary medicinal products and medicated feed.

The European Surveillance of Veterinary Antimicrobial Consumption (ESVAC, 2017) for 2015 has just been published. The highest users of antibiotics in food-producing animals (F-PA) expressed in tonnes of active substance are summarised in Table 1, and compared with the usage divided by the amount of animal treated using the population correction unit (PCU) system, which is calculated for each species of animal or bird.

Spain and Italy as heavy users

Based on tonnage of antibiotics used Spain and Italy are very high users and when divided by PCU, they are still very high users. In contrast, Germany and Poland are quite high overall users but based on PCU are more moderate users. France and the UK are even lower users, approaching that of the Netherlands 64 mg/kg PCU and Denmark 42 mg/kg PCU, who have made great strides in this area.

Some countries are now starting to make some real progress in reducing their antimicrobial consumption and ESVAC made a comparison of use in 2010 and 2015 (see Table 2).

This shows that Spain and Poland have actually increased their usage of antibiotics but several countries have made substantial reductions and real progress during this time e.g. the Netherlands, Germany and France.

Germany and France reduced tonnage

Recent data has shown that Germany has continued this progress in 2016, by reducing the tonnage consumed to 742 tonnes, a further 8% reduction from 2015. France has also reduced its consumption, especially of the more critically important antibiotics (CIAs) by greater than 75%.

Germany and France have managed to reduce their antibiotics consumption in recent years. Photo: Henk Riswick
Germany and France have managed to reduce their antibiotics consumption in recent years. Photo: Henk Riswick

These compounds that include the 3rd and 4th generation cephalosporin (ceftiofur; cefquinome) the fluoroquinolones (enrofloxacin; danofloxacin; marbofloxacin) and the polymixin (colistin) are coming under strong pressure to reduce their use, so that the chances of resistance spread to man from animals are minimised as much as possible. Macrolides (tylosin; tilmicosin; tulathromycin; tylvalosin) are also considered CIAs by the World Health Organisation (WHO) but in the EU they are considered of low or limited risk to public health (Category 1).

UK: more decrease of antibiotics

In the UK, the Veterinary Medicines Directorate (VMD) have also just released their latest antibiotic sales figures for 2016 and these have dropped further by 61 tonnes to 337 tonnes, a further 17% drop in usage and this has brought the mg/kg PCU figure down to 45 or a drop of 34% from 2010.

This has been due to extensive reductions in both the poultry (-71%) in 2016 and more recently the pig sector, by monitoring usage and consumption and making changes to management, housing, nutrition and improving herd health, to allow these improvements to occur. An overall national target was set at 50 mg/kg PCU by 2018 but this has been exceeded already to 45 mg/kg PCU in 2016.

Individual species targets

Individual species targets have now been set by species working groups under the supervision of the Responsible Use of Medicines in Agriculture (RUMA) Alliance to be implemented over the next 5 years and it is hoped to reduce the pig use of antibiotics by 62% from the estimated 2015 baseline of 263 mg/kg PCU to 99 mg/kg PCU by 2020.

Read more about pig health in the Pig Progress Health Tool

This really is outstanding work, and I must admit, as a cautious rather conservative observer, I thought it would be unlikely to achieve such an ambitious target but it seems that it can, with the full backing of the UK pig industry behind it.

Legislative matters

The Estonian Presidency is pushing forward on the Veterinary Medicinal Products and Medicated Feed legislation. I have commented before on some of this legislation but feel there are a couple of aspects that I would advise representative and national bodies to challenge and reject.

In the Veterinary Medicinal Products legislation under section 3, ‘Use’, they have put in on page 134:

“Article 111a

Use of antimicrobial medicinal products

1. Antimicrobial medicinal products shall not be applied routinely nor used to compensate for poor hygiene, or inadequate animal husbandry or lack of care or to compensate for poor farm management.

1a. Antimicrobial medicinal products shall not be used in animals for the purpose of promoting growth or increase yield.

2. Antimicrobial medicinal products shall not be used for prophylaxis unless, in exceptional cases for the treatment of a restricted number of animals when the risk for infection is very high and the consequences of the infection are likely to be severe.”

The above is quite reasonable and becoming largely accepted.

Prophylaxis usage

However, they have slipped in the following:

“2aa. Antibiotic medicinal products shall not be used for prophylaxis unless in exceptional cases for the treatment of an individual animal when the risk of development or spread of infectious disease is very high and the consequences of the infection are likely to be severe.”

This is unreasonable and shows a complete lack of understanding of population medicine to restrict it to an individual animal. The restrictions above regarding preventive use are sufficient, this paragraph (2aa.) is too restrictive and I can only advise that it should be challenged and withdrawn or you will lose preventive use totally in pig, poultry and calf medicine.

Illustration of an E. coli bacterium, one of the pathogens against which antibiotics may be used. Illustration: Shutterstock
Illustration of an E. coli bacterium, one of the pathogens against which antibiotics may be used. Illustration: Shutterstock

Medicated feed legislation

Similarly, in the Medicated Feed legislation on page 38 they have inserted a table in ANNEX IIA, which refers to maximum residue levels of cross-contamination (no longer carryover) for active substance of veterinary medicinal products in feed. They are pursuing a carryover of less than 1% and have set targets for carryover for particular medicines. For amoxicillin it is 0.5 mg/kg or 0.5 ppm. If it is included in feed at 400 ppm this represents a 0.125% carryover rate. Some of the others are more moderate, tetracyclines are 2 ppm but even so when included at 400 ppm it is still only 0.5%.

This is too restrictive and should be challenged.

A 3% carryover

Most feed companies can work with 3% carryover but this very restrictive level will lead to the effective ban of medicated feed, as nobody will be able to comply. For over 12 member states where medicated feed/feed premixes comprise more than 40% of their antibiotic use, this could be extremely critical.

These include the countries Spain, Italy, France, Portugal, UK, Ireland, Bulgaria, Cyprus, Finland, Hungary, Iceland and Slovakia.

If countries want to be able to continue to use medicated feed, this legislation needs to be challenged and blocked.

Classification of antibiotics

Finally, this brings me on to the classification of antibiotics in the EU. Most bodies have 3 classifications so that it allows grouping of front line use products, second line use products and ones that are considered critical and their use is last resort. In the EU we have:

• Category 1 - low risk to public health;

• Category 2 - higher risk, which includes the last-resort/critical drugs; and

• Category 3 – which are not used in veterinary medicine.

I think it would be timely to introduce 3 categories of use for veterinary medicines, such as low, intermediate and high risk/last resort antibiotics and a further category 4 for antibiotics that are not used in veterinary medicine but in human medicine only.

A new dividing line

A dividing line could easily be drawn here. For example, the aminoglycosides are coming up for review by the European Medicines Agency (EMA), they could make streptomycin Category 1, neomycin, kanamycin, etc. Category 2 and gentamicin and apramycin Category 3.

The products that are not currently licensed for veterinary use, such as tobramycin and amikacin could be in Category 4 and basically would not be used or available for veterinary use.

Penicillins and cephalosporins

This could also apply to penicillins and cephalosporins:

• Category 1 could be beta-lactamase sensitive penicillins (penicillin V and G) and beta-lactamase resistant penicillins (oxacillin and cloxacillin);

• Category 2 could include extended spectrum penicillins (amoxicillin and ampicillin) and 1st and 2nd generation cephalosporins;

• Category 3 could include penicillins + beta-lactamase inhibitors and 3rd and 4th generation cephalosporins.

This would thereby protect the more advanced human use products from veterinary use, like the ureido-penicillins, carbapenems, monobactams and 5th generation cephalosporins in Category 4, and reduce the potential impact of any antibiotic resistance development in animals, which may be then transmitted to man.

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