Antimicrobial Use in Swine Production

David G S Burch
BVetMed Dipl.ECPHM FRCVS Veterinarian, Octagon Services Ltd

Interviewed by Dagmara Chelstowska of "Hoduj z głową. Świnie" in 2013

By way of introduction, David is a Diplomate of the European College of Porcine Health Management i.e. a specialist in pig medicine, especially antibiotic use, and recently has been appointed to the European Commission's European Innovation Partnership (EIP) Focus Group 'On the reduction of antibiotic use in the pig sector'.

Q1. Is it possible to manage swine production without antibiotics?

A1. A number of farms have tried to be antibiotic free, with mixed success. Much of the new Brachyspira hampsonii problems in Canada, which causes a similar, severe disease to swine dysentery, first started on farms that were trying to be antimicrobial-drugs free and possibly it is the lack of antibiotics that have allowed this new infection in and to take a hold. It is possible that the use of antibiotics, even as growth promoters would have masked or prevented the infection taking place. It is difficult to be totally antibiotic free and I think we can turn the question round to do we need to be antibiotic free? Animals get ill just like human beings; they suffer from a number of virus infections, which predispose them to secondary bacterial and mycoplasmal infections as well as primary infections, so why should we not treat sick pigs. It is good for both the welfare and health of the pig and enables the farmer to maintain his production efficiency and hopefully profitability, otherwise he will go out of business. The problems have arisen from what antibiotics we use and how reliant we have become on their use - are we over-using them?

Q2. What are the most common health problems that swine operations have to face?

A2. This depends to a certain extent where you are in the world, some countries have foot and mouth disease, classical swine fever, African swine fever, Aujeszky's disease to contend with, as well as what I consider the more common diseases that affect most herds. Most EU herds have been hit with porcine circovirus type 2 (PCV-2) problems in the last decade but this has been largely controlled by highly effective vaccines. Other viruses such as porcine reproductive and respiratory syndrome virus (PPRSV) are still circulating in Europe, but fortunately we have the milder European strains and US vaccine strains present, unlike the US, which has a much severer form of the disease. Both PCV-2 and PRRS are immunosuppressive, so this enables bacteria to penetrate the pig's body and cause secondary infections, especially pneumonias, which can cause an increase in antibiotic use as a result.

Swine influenza viruses are also a potential problem and new strains have recently caused some major problems here in the UK. Porcine epidemic diarrhoea virus (PEDV) is causing a major problem in the USA and seems to be related to the severe Asian strains. Europe has its own strains circulating at a low level but it is not clear yet whether these will protect against the US strains if they are introduced here. From a bacterial perspective, all pigs have a check at weaning, associated with Escherichia coli and many diets (80-90%) will contain either zinc oxide, in the countries that permit it, or antibiotics to prevent post-weaning diarrhoea and possible death. Water medication is also a common option and injections for the sicker pig.

Swine dysentery is not so widespread but it has caused problems in some countries and antimicrobial resistance development has been reported as a major issue, e.g. Spain, Italy and Belgium due to the need to continuously treat infected pigs. Much higher control on the sale and movement of infected pigs is required. Ileitis caused by Lawsonia intracellularis is also widespread and is controllable with a vaccine but many farmers prefer to use medication in growing pigs and allow natural immunity to occur. Respiratory-wise, Actinobacillus pleuropneumoniae is common still, as well as Mycoplasma hyopneumoniae; both are primary infections and are still problematic, although vaccines are used to control them. Haemophilus parasuis and Streptococcus suis are also still circulating and frequently made worse by PRRS infections. Vaccines can be used but medications such as penicillins and cephalosporins are also popular and effective. Establishing disease-free farms is one way to reduce medication with antibiotics, e.g. swine dysentery and enzootic pneumonia-free farms use much less antibiotic. The problems remain though of biosecurity and here we can make greater improvements to keep diseases out.

Q3. Do swine diseases have a seasonal nature or do their prevalence depend on other factors?

A3. Generally, respiratory diseases are worse in the winter than the summer - think of the common cold and influenza in man. To preserve heat in a building, the compromise is to reduce ventilation. This allows the spread of viruses and bacteria in the atmosphere of a building to move more easily from pig to pig. Enzootic pneumonia lesions at slaughter were always classically higher in pigs during the winter and spring when pigs have been housed through the cold months. In Poland particularly, the winters can be very cold, so good insulation and temperature and ventilation control is important. Regarding enteric disease, piglets and weaners are very susceptible to cold temperatures and fluctuations in temperatures, such as at night time. Chilling will induce or increase the severity of enteric disease, especially E. coli diarrhoea. In spring and autumn possibly due to the variations in temperature and humidity, streptococcal meningitis is reportedly to increase in weaners and growers. Generally, in the summer ventilation is better and respiratory infections are lower.

Q4. Before introducing antibiotic treatment on a given swine operation, what should be definitely done regardless of costs?

A4. This is an interesting question and has received much comment in recent times regarding the 'responsible use' of antibiotics. Ideally, a sound diagnosis of the problem is critical. Is it viral, is bacterial is it new or is it a recurrence of an old disease? Practitioners and farmers are considering these aspects all the time. The history of the farm is important. Have new animals been brought on to the farm (can they have brought a disease in with them); has the farmer changed something management-wise - a new building, changed the age of weaning, stopped cleaning, replaced a member of staff, especially in the farrowing area etc. If there are dead pigs, a post-mortem examination is the best approach to see what is going on. Samples can be taken for histology, virus and bacterial isolation and blood can be taken for serology. If a bacterium is cultured and thought to be responsible e.g. E. coli, an antimicrobial sensitivity test can be easily and quickly carried out. Some bacteria and mycoplasma are very difficult to grow, but even in the case of Brachyspira hyodysenteriae it is important to start the process and many companies will support this, if sent to specialised laboratories. These tests then confirm which sensitive antibiotics can be used. In some countries they are introducing first, second and third line drug treatment and to use the second or third line (fluoroquinolones and 3rd and 4th generation cephalosporins) a sensitivity report to show this is essential. If the first line drug is not working, then you can switch quickly to one that will. Always remember though, infections and disease are frequently management related - one of the main challenges of pig medicine - and this must also be looked into - what am I doing wrong?

Q5. When the treatment is ineffective despite the proper choice of antibiotic, what should be done then?

A5. I have touched on this in A4. Check the management. If it is an E. coli problem post weaning it is usually associated with cold temperatures or fluctuations in temperatures. If the pigs are being chilled they cannot fight this and therefore maximum/minimum thermometers are essential in flat decks. In the UK we can wean into straw yards, where the pigs can bury themselves and keep warm enough, even in our harshest winters. With some antibiotics, especially with swine dysentery, sometimes the pigs come off the antibiotic and breakdown again within 2-3 days. The antibiotic is at an inhibitory level only and is not eliminating the infection, so when you stop it, the disease comes back quickly. In some cases it comes back after 3 weeks and the antibiotic has worked but the pigs have usually become re-infected from the environment. Hygiene measures are also important in these cases to prevent re-infection. It is sometimes difficult where you have solid-floor, scrape-through systems as in the UK.

Q6. What ways/methods of limiting the use of antibiotics on swine operations would you recommend?

A6. This is sometimes very difficult as each farm is different, whether they are breeder/weaner, grower or finisher producers. Firstly, don't let the disease in. Ideally, if you start with disease-free stock then the use of antibiotics is much reduced, possibly to only individual treatments with injections. Secondly, good biosecurity - keep diseases out; do not tolerate suppliers of weaners or growers that carry swine dysentery for example. Do not buy from them again. If you have a multi-resistant infection like B. hyodysenteriae, take the opportunity to depopulate the farm; clean, disinfect and repair and repopulate with high-health stock. Do not share transport or workers if possible. If you have to, make sure lorries/trucks are thoroughly clean coming on to your unit and workers can change into fresh clothes and boots. Buy in breeding stock from reputable companies, again so not to buy disease in.

Unit isolation is also important. It has been shown that PRRS virus and M. hyopneumoniae can travel up to 9km if the weather conditions are right and a plume of infection travels your way. The further away you are from other pig farms the better. Review your antimicrobial and vaccine programmes on a regular basis with your veterinarian. Look at what you are doing and how often you need to treat your animals. Are there areas that treatments can be reduced or dropped? Many of the new monitoring schemes in Denmark and Netherlands look at daily doses and set limits. These can be helpful but they are quite complicated. Germany is introducing a treatment-day system, which has some advantages as you can put on a spreadsheet how you are using antibiotics and can then visualise possible reductions in use more easily rather than just using a benchmark figure.

Generally, we do use a lot of antibiotics in pig production and much of this is because we have evolved as an industry and have lived with our older buildings and methods of production. Antibiotic use or over-use was a back up to these systems. I think in the future there will be more controls over antibiotic usage so farmers must look to their production systems and try to improve them. Use more vaccines if available, especially to prevent respiratory diseases and some enteric diseases. Improve biosecurity and where possible improve the health status of their herds.


Copyright © Octagon Services Ltd  2013

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