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Highest recorded PRRS diagnosis in first quarter

17th Jul 2018 / By Alistair Driver

The first quarter of 2018 saw the highest ever recorded diagnostic rate of PRRS, according to the latest GB Emerging Threats Quarterly Report. 

The Animal and Plant Health Agency report highlights that total GB diagnostic submissions to APHA and SAC CVS from pigs in January to March 2018 were 7% down on the average of the previous four years. 

The full report can be found HERE.

It contains information on ongoing, new and re-emerging disease investigations and changes in disease patterns and risk factors, including:

  • The spread of African Swine Fever into Hungary 
  • Typical winter rise in PRRS diagnoses 8
  • Swine dystentery cases in Yorkshire
  • Novel bat-derived enteric virus in pigs in China 11
  • Brachyspira suanatina detection in pigs in Germany 

ASF

ASF update map

The continued westward spread of ASF emphasises the need to raise awareness amongst all pig keepers across Europe of the need to take stringent external biosecurity precautions to reduce the risk of introduction, the report says.

Key messages include:

  • Not feeding kitchen and catering waste to pigs and, particularly, preventing feeding pigs with pork or wild boar meat or products
  • Providing dedicated clothing and boots for workers and visitors
  • Limiting visitors to a minimum
  • Preventing outside vehicles which may be contaminated from coming on to the farm. 

An ASF poster for pig keepers has been produced as part of this campaign. 

ASF poster 2018

The report notes Information from a publication modelling ASF transmission emphasises that, contrary to some traditional textbook descriptions, the spread of ASF by pig to pig contact can be slower than for some other diseases, such as classical swine fever). 

If infection is first introduced into a small number of pigs in a group, disease initially only involves those few pigs and spread of infection to larger numbers of pigs, leading to higher than expected mortality, can take several weeks.

This slower spread on pig farms supports enhanced passive surveillance for ASF in restricted and at risk areas to enable early detection of ASF cases even where the mortality has not yet significantly increased.

PRRS

The diagnostic rate for PRRS in GB in the first quarter of 2018 was the highest recorded quarterly diagnostic rate (16.6%) with the previous highest being in Q4 2016 (12.7%).

The seasonality pattern with a peak in diagnoses in winter months and dip in summer months is familiar. This data supports anecdotal reports from pig practitioners of continued clinical problems associated with PRRS.

The rise may well reflect better survival and transmission of the virus in cooler, darker and less dry weather conditions, as well as colder wetter weather making effective cleaning and disinfection harder to achieve. Temperature fluctuations and ventilation issues that can occur over the winter months may also contribute to PRRS as for other respiratory diseases.

The majority of diagnoses were made in submissions from pigs in England.

Swine dysentery 

There have been four further diagnoses of swine dysentery in Q1 of 2018, all in South or North Yorkshire.

Control of swine dysentery using alternative interventions (all-in, all-out management systems; cleaning and disinfection; and partial and total depopulation leading to eradication) is vital to prevent the development of wider antimicrobial resistance, the report said. 

AHDB Pork have been promoting awareness of the Significant Diseases Charter amongst producers and encouraging them to sign up and declare diseases such as swine dysentery, should they be diagnosed.

Novel bat-derived enteric virus in pigs in China

A letter in Nature describes a novel enteric coronavirus, distinct from PED and TGE, causing diarrhoea and high mortality in neonatal piglets in China in 2017.

Evidence indicates the virus recently moved from horseshoe bats into pigs and the index case herd is in a region fairly close to where severe acute respiratory syndrome (SARS) emerged in humans from bats via an intermediate host.

Brachyspira suanatina detection in pigs in Germany

Brachyspira suanatina has previously only been described in pigs in Scandinavia in 2007. The first description of B. suanatina infection in pigs outside Scandinavia has been recorded in Germany. It confirms the ability of this Brachyspira species to cause severe swine dysentery.

The paper also describes several other detections of B. suanatina in Germany in healthy breeding sows and in fattening pigs with diarrhoea. Pathogenic Brachyspira species are spread by the faeco-oral route. It is likely that the same risk pathways exist for introduction of B. suanatina into the UK, and into pig herds, possibly by importation of clinically mildly or asymptomatically infected pigs, the update warns. 

In this context, it highlights the NPA's voluntary import protocol, which has practical advice on biosecurity including quarantine when importing pigs to the UK.

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