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PMWS Update from PIPS
PIPS/MLC Meeting - This document summaries a number of the issues that were discussed and came out of the PMWS conference in Leeds/Selby, UK in November 2001. The main issues regards Controlling PMWS and PDNS are covered in our main "Controlling PMWS" Document.

PIPS meeting notes

At the end of November 2001, PIPS and MLC joined forces to host a conference on PMWS in Yorkshire. Over 180 people attended the conference and below we have briefly tried to summarize the proceedings.

There was no specific groundbreaking news with the majority of the speakers reinforcing what has been said previously. However, Jake Waddilove and Paul Day reported some interesting developments in the field of serology which may prove promising in helping to control the disease. However, this news comes with a "health warning"!

Paul Day - Comfoot Flooring / Unit Manager for J. D. Alston Estates.

Paul reported on the serology work that was being conducted on his farm by Jake Waddilove (see below).

Jake Waddilove - East Anglian veterinarian

Jake Waddilove spoke about his work on Paul Day's farm in East Anglia where he was trying a technique called serotherapy. Results of sero-vaccination (serotherapy) work in Spain presented at the recent St Malo conference showed circa 10% reduction in mortality from using this technique.
     Jake explained that a batch of 105 pigs have been treated with serum and were being monitored against a similar batch of 120 untreated pigs.
     At the time of speaking, the group of pigs were 12 weeks old and 5 of the controls had died from, and 20 were showing signs of, PMWS. The treated group all looked healthy. Since then 6 of the treated pigs have succumbed, but this is a considerable reduction on the number of controls affected.
     In a more recent development, a batch of 30 older pigs showing signs of PMWS have been treated with the serum. This would appear to have been successful in that the majority of these pigs are reported to have recovered and are be growing normally.
     However, Jake warned that this procedure is a controversial technique. Strict veterinary supervision is required and the serum collected for a farm MUST come from pigs on that farm to ensure the Medicines Act is not contravened.
     We are being specifically vague on this process as work is ongoing by Jake and Mike Muirhead to develop an agreed protocol for the procedure. This is being treated as a matter of urgency and we will keep everyone updated as to the process as it develops.

Derek Armstrong - MLC veterinary scientist

Derek highlighted what appeared to be the two most likely reasons for a farm contracting PMWS. He explained that research has shown that herds within three kilometres of an infected herd are nine time more likely to get the disease.
     Current research also indicated a correlation to the number of gilts you bought in. "This potentially indicates that you can buy in the disease," he said. "But you need to be very careful about reading too much into these findings." This is re-inforced by the fact many farms who have contracted the disease have not bought a pig onto the farm for "years".
     Derek refuted claims by vegans that PMWS is a symptom of UK farming methods and he questioned claims by the UN Food and Agriculture Organisation that the disease is a "European problem".
     "It is not an English problem, nor even a European problem," he told the conference. "It is a worldwide problem."

For more details see Derek's Paper below.

John Evans - Midland Pig Producers

John explained that Midlands efforts with the 20-point Madec plan had been fruitless, highlighting what most people now recognise, that there is no cure all for this problem. Interestingly, John said that their "very best unit" was the first to fall to PMWS? " exactly one year ago.
     The key point that John raised was the issue of bringing breeding stock onto the farm. He indicated they were thinking about "shutting the farm gate very firmly", stopping the movement of animals onto the farm altogether and using AI.
     John felt that it was too easy to dwell on genetic improvement when biosecurity and health status were the biggest drag factor in the industry.

Mark Hayward - Producer

Mark raised the point in his talk of the need for farmers to co-operate in fighting the disease. He suggested farmers group together and each try different a approach to see which works best for them. Although each farm is different Mark highlighted that all farmers trying the same thing at once "wasted months of effort".
Mark highlighted four actions he felt had made the biggest difference:
1. Wean bigger and stronger pigs.
2. Reduce the viral plume - remove sick pigs promptly
3. Reduce stress - especially NO mixing
4. all-in all-out with excellent cleaning and disinfection

Mick Sloyan - BPEX Manager

Mick expressed his concerns over the "parochial" approach to tackling the problem and said. "It's very, very important from a BPEX point of view that we get as much knowledge about what's happening in the EU into a co-ordinated framework." He explained there have been meetings at a scientific level within organisations similar to the MLC and rest of Europe, and at a political level. NPA were briefing European farmers about experiences within the UK, and calling on them for a co-ordinated approach to the European Commission for a framework whereby countries and researchers could communicate with one another, he said. And he called for more money for research. Some research could deliver short-term benefits - such as Jake Waddilove's current work with serotherapy - but we also needed longer term research to manage our way out of the crisis, he said.

Henrik Baekstrøm - Danish Bacon & Meat Council

Henrik gave an overview of PMWS in Denmark and also of the Danish production systems. To date only four farms have contracted "clinical" PMWS, however indications are that the PCV2 virus is present in most herds. Henrik suggested some possible reasons why the Danish herd had, to date, shown little susceptibility:
     The Danes made a decision several years ago to breed out the halothene (stress) gene from their breeding herd. This has resulted in a significant reduction in transport mortality, but could also be helping with PMWS.
     Fish meal can still be fed to pigs up to 40kg. Certainly there is evidence that there is a dietary effect and this may be helping.

Paper by Derek Armstrong - MLC veterinary scientist

PMWS was recognised as a new disease in Canada in 1995, although the first case dated back to 1991. In the UK the first cases were identified in 1999 although it is possible there were some cases as early as 1995. The French first started reporting the disease in 1996 and the Spanish in 1997. Studies of stored samples and records suggest that there may have been cases in Spain as early as 1986.

PMWS is a disease that is present worldwide. It has been reported throughout the EU and in Asia, the U.S. and Canada. Despite all the evidence that this disease is a worldwide problem an official at the Food and Agriculture Organisation has released a statement which paints it as a European or an English problem. In addition a vegan organisation has been claiming that it is due to farming practices in the UK totally ignoring the fact that it is a major problem elsewhere in the world.
When the first cases were seen in East Anglia the Veterinary Laboratories Agency (VLA) in Bury carried out work to define the clinical signs and the pathology so it could be confirmed what was PMWS and what wasn't. This was important since a whole range of other diseases can cause wasting in pigs.

At Weybridge the VLA have been working on the development of diagnostic agents and also on analysis of the genome of Porcine Circovirus 2 (PCV2). A full analysis of the genetics of a virus is a complex and expensive procedure. There could be quite small changes in genes that haven't yet been picked up in PCV2. If there has been a significant change in the genetic makeup of PCV2 it could explain why the virus which has been around since the 1970s has only been associated with serious disease since the 1990s.

British Pig Executive and MLC allocated ?135,000 to fund research on PMWS to date. There is a research project looking at the importance of colostrum and virus transmission around the time of farrowing. There are also some preliminary studies looking at PCV2 and semen. Further studies are looking at the impact of enzootic pneumonia vaccination on the severity of PMWS and the importance of any litter effect on incidence in pigs.

In addition there is an extensive programme of research in a lot of other countries and BPEX is endeavouring to make sure there is better co-ordination and a sharing of information between all countries.

Less duplication and more integration in this respect will help the pig industry get to the bottom of PMWS more quickly. At present we can liken the situation to a jigsaw puzzle where all the pieces are spread all over the floor and we're gradually piecing it together one piece at a time.

The EU have funded three different programmes of research which involve PMWS and PCV2. The two main studies are being led by The Queens University of Belfast and the University of Barcelona. Both these programmes are looking at developing diagnostic methods, the epidemiology of PMWS and also the development of a vaccine. A third programme at the Institute of Animal Health, Compton is investigating the possible use of another virus to create a vaccine against PCV2.

There is still a lot of development and testing work to be done before a vaccine can be launched. Even if the development work were completed tomorrow, it would probably take a year to get through registration. So a vaccine is not going to be an answer in the short term, which is why we still need to concentrate on management and husbandry control procedures.
PMWS virus
PMWS is one of the smallest viruses and also one of the most hardy viruses. It is extremely resistant to heat. Once you've got it on a farm it's very difficult to eliminate.

One the things that seems to be important in controlling PMWS is to reduce the amount of virus that is being spread around the farm. This may help reduce the dose of virus which pigs pick up and may also help to delay the age at which pigs are infected by the virus.

PCV2 is resistant to most disinfectants. In research in the U.S. Virkon S was the only one to give a 4-log reduction. But it is important to remember that this was in a laboratory where there was no dirt to which could interfere with the activity of the disinfectant.

It is very important when we think about cleaning and disinfecting to get the cleaning part right before we start applying the disinfectant.

Interestingly the next most effective disinfectant was sodium hydroxide - or caustic soda - and there are certain health and safety implications to think of before splashing that around!
PCV2 virus
There has been a lot of laboratory research on PCV2 worldwide. It has been shown in laboratories that PCV2 on its own can cause PMWS under certain circumstances. If pigs are co-infected with another virus at the same time or shortly afterwards (for instance Porcine Parvovirus and PRRS) the severity is much increased.

One of the big questions is, whether there been a change in PCV2 which has increased the virulence of PMWS. There is no convincing evidence of significant changes at this stage but there is still a lot of work to be done on this area.

Most vets in practice would agree that PMWS in England has behaved just like a new infectious agent. It is like when we first saw Blue Ear and it spread so quickly. The major difference with PMWS is that we don't appear to see a build up in herd immunity and resistance to PMWS.
Risk factors
The VLA carried out a study comparing PMWS affected farms with farms that did not have PMWS in early 2001. The most important factor in PMWS was proximity to other affected herds. Herds with PMWS and PDNS were nine times more likely to be within three kilometres of another affected herd. There have been similar results in France, where PMWS affected farms were likely to be closer to other farms. This would tend to support the suggestion that PMWS is acting like a new infectious agent.

There have been suggestions that birds may have been involved in transmitting the disease but there is no conclusive evidence either way. In Canada PMWS was first seen in the most biosecure herds and most herds are also more than five kilometres from each other. So the reasons why PMWs spreads are still unclear.

In the VLA study herds affected with PMWS and PDNS also tended to be larger and to be purchasing more gilts. PRRS, Salmonella and Coccidiosis were reported more frequently in affected herds.

It is important to remember to be careful when drawing conclusions from this type of epidemiological study. When the plague was in London somebody noticed that cats and dogs were more common in the poorer areas which were more heavily affected with the plague. So then they killed out all the cats and dogs - allowing rats to increase and spread the plague! The reason there may have been more cats and dogs may have been that there were more rats in the poorer areas the first place.

So you have to be careful about interpreting this type of research. The fact that affected farms were purchasing more gilts might indicate that purchased animals were more likely to be affected but could also simply be a reflection that affected farms were bigger and bought more gilts. The reason bigger farms are affected by PMWS may be totally unrelated to their gilt purchase policy.

Nevertheless, in this study the key risk factor was proximity to other pig farms. This highlights once again the importance of good biosecurity to keep disease out of pig farms. A similar but more detailed case:control study has been carried out in France and results should be available in early 2002.
At present there is no specific treatment available for PMWS. The mortality rate is virtually 100% in clinically affected animals. Cohort studies in France in 1996-97 identified hard management practices as potential contributing factors to severity of disease. Professor Madec and his colleagues in France developed a programme of 20 zootechnical recommendations as a guideline for severely affected farms.

Reports from France indicate that these recommendations have helped to reduce losses on PMWS affected farms. Attention to detail has been the key and it would appear that for maximum effect 80% of the recommendations have to be put into action. The main effect of these recommendations is to reduce the potential for other diseases, especially gut and respiratory diseases to affect the pigs. New viral diseases seem to emerge regularly in the world pig population - Parvovirus, PRRs and now PMWS. The AFSSA recommendations should not only help control PMWS but reduce the possibility for spread of any other new disease in the future.

All husbandry and management procedures on farms should be looked to see if they can be changed in any way so that either pig to pig contact is reduced, and/or stress on the pigs is reduced and/or hygiene is improved. The procedures adopted will vary from farm to farm because all farms are different.

Some suggestions, such as later weaning or structural changes to buildings, may add significant costs. It may be useful to think laterally and for example look at using general purpose buildings as deep litter pens to create a break in a cycle or to reduce stocking density. It may also take time to implement some of the changes but they can be introduced step-by-step.

Other strategies, such as the suggestion to vaccinate sows against Parvovirus and PRRS pre-farrowing to improve the passive antibody transfer, are either unproven or may be significantly affected by the circumstances on different farms. Where it is practical on-farm trials should be considered before adopting changes. A group which has received the treatment should be compared with a second group managed in exactly the same way except for the specific treatment and the effects observed. Because mortality rates can vary over time the two groups should be investigated at the same time if possible. It is also important to remember that with PMWS it may take some time before the changes take effect. It may be necessary to carry out trials for some months to check if the changes are effective in reducing the impact of PMWS.

PMWS is a very complex disease and there are no easy answers to either the research questions or in the control of the disease on farm. There is a lot of research in progress worldwide. Every effort is being made to check the information produced by these studies to see if it could be of value in controlling PMWS on British pig farms.

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