Salmonella in Livestock Production in GB - 2009 - Pigs

by 5m Editor
18 January 2011, at 12:00am

This annual publication from the Veterinary Laboratories Agency provides data on Salmonella reports from livestock species in Great Britain (England, Wales and Scotland). This article covers the chapter entitled 'Reports of Salmonella in Pigs'.

Results from the June Agricultural Census indicated little change in the size of the GB pig herd from 2008, down 0.5 per cent to 4.3 million head. However, within this total, the figure for Scotland declined sharply, from 436,000 animals in 2008 to 396,000 in 2009. In the same period, the UK female breeding herd increased by almost six per cent, recovering much of the loss evident in the previous year. Revised data from Defra for 2009 indicates 8.8 million pigs were slaughtered, four per cent fewer than in 2008. UK feed wheat prices were considerably lower in 2009 than in 20081, offering those producers who survived the high prices in 2008 the chance to create a margin in the production process.

A total of 5,334 pig submissions were received by VLA/SAC during 2009, down from 5,761 in 2008 and 6,176 in 2007. Diagnostic pig submissions however (which generate the bulk of Salmonella incidents in pigs) actually rose by a fifth from 1,490 in 2008 to 1,797 during 2009.

In December 2009, the European Food Safety Authority (EFSA) published the results of the 2008 EU baseline survey of Salmonella in holdings with breeding pigs. Holdings with breeding pigs were separated into two categories. Breeding holdings that predominantly sold gilts or boars for reproductive purposes and production holdings which mainly sold pigs for fattening or slaughter (commercial farms). The UK estimated prevalence for all Salmonella positive breeding holdings and production holdings was 52.2 per cent and 44 per cent, respectively. This was higher than the mean weighted EU prevalence of 28.7 per cent and 33.3 per cent for these types of herds. This survey followed the publication in 2008 of the EFSA report on the results of the 2006-2007 survey of Salmonella in slaughter pigs. Interestingly, some countries with very high prevalence of Salmonella in breeding pigs had a proportionately lower level in slaughter pigs. Salmonella Derby was the most commonly detected serovar in the survey across Member States, and in the United Kingdom, S. Typhimurium was most commonly isolated serovar. Part B of the EFSA report, due to be published in 2010, will give further information on the S. Typhimurium phage types identified, as well as the results of risk factor analyses.

2009 saw the British Pig Executive’s Zoonoses National Control Programme for pigs (ZNCP) enter its second year of operation. Under this programme assured herds receive four-monthly reports containing their rolling annual meat juice ELISA results. Producers are encouraged to aim for <10 per cent of results in the positive or weak positive categories, and all units must maintain and demonstrate progress against a Salmonella Action Plan. While the rolling 12-month average in England was stable through 2009 at approximately one in every two samples testing antibody positive or weak positive, the percentage in Scotland has shown a slow increase from 22 per cent to 25 per cent. VLA continued to support the programme by agreeing to visit eligible holdings to collect samples and assess the effectiveness of Salmonella control measures, producing a report for the producer and his/her veterinary surgeon. Sixteen visits were completed during 2009, with 1,497 samples taken for Salmonella testing at VLA. There is a concern that breeding herds may be a reservoir of Salmonella for finisher units, and a small number of visits were specifically directed at holdings higher up the production chain. Of particular interest was the isolation of Salmonella Panama from two herds. This group D serovar is currently rarely reported from UK farms, having previously been isolated once in the last six years, although it was more prominent previously.

Table 4.1 shows the overall number of Salmonella incidents and isolations recorded from pigs over the past five years and Figure 4.1/Table 4.2 the proportions afforded by the most frequent serovars. There were 182 incidents of Salmonella in 2009, which is similar to 2008 (183 incidents) but there were subtle changes in the prominence of minor serovars.

Figure 4.1. Incidents of Salmonella serotypes in pigs in 2009

Figure 4.2. Incidents of Salmonella Typhimurium phage types in pigs in 2009

Salmonella Typhimurium remained the most commonly found serovar. It was detected in 129 incidents in 2009, the highest number since 2003. In terms of its animal and human health implications, Salmonella 4,5,12:i:- is considered to be an important variant of S. Typhimurium and was responsible for two significant outbreaks in humans in Luxembourg. Its relative contribution has risen steadily since 2005 and was the second most common serovar isolated in 2009 (12 incidents; 6.6 per cent of the total). Salmonella Derby was the third most common serovar in 2009, though its relative contribution was less than a third of the level observed in 2005. Fewer than half as many incidents of S. Reading and S. London were detected in 2009 than in 2008, while S. Rissen, a serovar of feed origin, absent from the tables before 2008, contributed seven incidents in 2009.

In 2008, Salmonella Enteritidis and S. Montevideo were reported in pigs for first time for five years. Neither was identified from routine surveillance in 2009. Serovars newly reported in the year included S. Choleraesuis (var Kunzendorf), last reported in pigs in 2001, and S. Kimuenza which was last reported in 2002 (but which was also reported from research work in 2008).

DT193 and U288 continue to be the most commonly identified definitive (DT) and undefined (U) types of S. Typhimurium (Table 4.3) and phage typing defined nine of the 12 incidents involving S. 4,5,12:i:- as DT193. Salmonella Typhimurium definitive types DT12 and DT30, last reported in pigs in 2003 and 1998 respectively, were identified on a small number of premises during the year. DT1, which has been reported previously in other livestock species (including cattle, horses, chickens turkeys and wild birds), was reported in pigs for the first time. U311 was also identified for the first time in pigs; the last report from routine surveillance having been in 2003 from cattle.

In 2009, there was one Salmonella report of non-GB origin from imported pigs; this was a report of S. Typhimurium U288 which has been excluded from the tables and figures of this publication.

1 Information on UK feed wheat prices supplied by the Agriculture and Horticulture Development Board.

Further Reading

- You can view the full chapter Reports of Salmonella in Pigs (including detailed tables) by clicking here.

Further Reading

- You can view the full report Salmonella in Livestock Production in GB 2009 by clicking here.

January 2011