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Tackling disease in pigs

Dr Susanna Williamson leads scanning surveillance activities for pigs at the APHA to detect, investigate and tackle new and emerging disease threats. She has been involved in the diagnosis and investigation of many disease outbreaks in pigs, as well as projects on bacterial and viral diseases.


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Dr Susanna Williamson discusses pig diseases and how to tackle them #Pigs

Dr Williamson was recently awarded the 2016 David Black Award which goes to somebody who has made a valuable and sustained contribution to the British pig industry.

How did your professional interest in pigs develop?

My interest in pigs and pig diseases developed when I moved to work as a Veterinary Investigation Officer (VIO) at the Bury St Edmunds Veterinary Investigation Centre to work in the Veterinary Laboratories Agency (now AHPA) team there in 2000.

Why is the level of disease risk and its potential impact in pigs so high compared to other livestock species?

One of the differences between pigs and ruminants is pigs breed all year round. This means there is no significant break between successive batches of young pigs as there is for cattle and sheep. Also, each sow produces a high number of young at each pregnancy comparted to ruminants; typically around twelve pigs per litter and so 90 percent of the commercial pig population at any one time is under six months old. As a consequence, more of the population is susceptible to infection and disease due to their naïve status because they have not previously encountered infections in their lifetime.

What are the most serious disease threats facing the UK pig industry today?

African Swine Fever (ASF) is an ever present threat because it is persistent in countries bordering eastern EU member states where ASF infections are detected regularly in wild boar and domestic pig outbreaks have been reported over the past three years.

Any spread of ASF westward within the EU is of concern. Countries like Denmark have stepped up pig transport biosecurity in response to the risk of spread on lorries returning from these areas. About 20 percent of lorries coming to the UK from Europe are from Poland and if there is any contamination of these with ASF-infected pig faeces, they represent a risk route for introduction. This emphasises the need for pig farmers in the UK to maintain the highest standards of biosecurity.

The highest risk of the disease entering pigs in the UK is through people feeding waste food containing meat from an ASF-infected pig or wild boar to pigs.

The feeding of swill to pigs has been banned since 2001 but almost a third of smallholder pig owners admitted to feeding food waste to their pigs in a recent survey. These actions, which may be done with good intentions, are illegal and pose a serious danger to the wellbeing of their own pigs and the entire pig industry.

A virulent strain of Porcine Epidemic Diarrhoea (PED) has been one of our biggest concerns since it was detected in late spring 2013 in the United States. It was found to spread rapidly, particularly via pig lorry movements due to ineffective disinfection procedures. It spread through the US and into Canada in less than a year.

The effects of the disease are devastating in young pigs; it typically results in 80 to100 percent mortality in pigs less than two weeks old. Consequently, Government and industry worked together to take action to reduce the risk of introducing the virus, to increase the likelihood of detection if it did enter and to establish control plans.

The disease was made notifiable in England and Scotland requiring pig keepers or vets suspecting PED to report it.


Dr Susanna Williamson.

What forms of surveillance do you use at the AHPA?

One form of surveillance we use we refer to as ‘horizon scanning’ where we monitor a range of sources to scan for infections and diseases which have not been detected in the UK but may be reported in other countries. We attend conferences, examine veterinary research publications and also keep an eye on relevant websites.

Diagnostic investigations taking place through APHA and SAC and discussions with veterinary practitioners attending disease outbreaks are another vital method of surveillance. Vets and farmers are the ‘eyes and ears’ for disease surveillance and we encourage practitioners to contact us where they suspect something out of the ordinary, for example where there are unusual signs or disease is severe or unresponsive to control measures.

Part of your role as the Veterinary Lead on pigs is to inform Defra and make recommendations about the seriousness of a disease. How do you quantify the level of risk and the impact of a disease?

There is a standardised approach which is overseen by the Veterinary Risk Group which reports to the four Chief Veterinary Officers. For each potential disease threat, we consider the impact of on pig health and welfare. Importantly, we assess any risk to human health. Finally we must assess the possible impact of the disease on international trade.

What technological advances do you think may make a real difference for pig health and welfare in the coming years?

I think vaccines have the potential to help us in the battle against many serious pig diseases. In 2006, PCV2 vaccines were introduced and have proven very effective against porcine circovirus-associated disease which caused huge losses from late 1999 when it appeared and spread in the UK.


However, there are ‘clever’ viruses such as Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) which mutates quickly and is therefore more challenging for the vaccine companies to produce fully effective vaccines. There is no vaccine available for use in ASF-affected countries. Investment in technological advances to produce new or improved vaccines could make quantum leaps in disease control for some diseases.

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