The EU salmonella baseline survey in pigs has now been released but where do we go from here?
The EU salmonella baseline survey in pigs has now been released but where do
we go from here?
We have surveyed over 19,000 pigs and their lymph
nodes and an average of 10.3% of all pigs going to slaughter carry Salmonella.
Salmonella enterica Typhimurium and S. Derby are the two
most common isolates, so no surprises there. S. Typhimurium was found in
4.7% and 2.1% were S. Derby, 'which are two common serovars found
in Salmonella infections in humans'. Is that so?
S. Typhimurium is
significant accounting for up to 20% of human cases but occurs in most animals
and poultry. S. Derby, which is primarily found in pigs, usually accounts
for less than 1% (the figure is often so low it is not recorded) and in a UK
survey in 2000, only 0.2% of human cases were associated, which can hardly be
called common. On a proportionate basis, Salmonella from pigs may only account
for 1.0% of human cases.
The second part of the study looked at contamination of the
carcass with Salmonella and the EU average was 8.3% (see Figure 1) and
3.9% for S. Typhimurium and 2.6% for S. Derby.
Interestingly, some countries had higher carcass contamination
than lymph nodes, suggesting that the carcass contamination is occurring in the
slaughter house. In most countries there is a fall, which fits in with good
slaughterhouse management and hygiene.IPVS Congress
recent International Pig Veterinary Society (IPVS) congress there was a very
interesting paper by De Busser and others (2008) from Belgium showing the impact
of the slaughter house on carcass contamination with Salmonella (see Figure
Samples from five
slaughterhouses at various stages of production were taken: - in the lairage,
after the scalding tank and polishing, after splitting of the carcass and
finally in the chilling room. Contamination of the lairage seemed to have the
most impact on subsequent carcass contamination and the difference between the
best and the worst slaughterhouses.
The best one had slatted lairage
floors. Carcass contamination usually goes up after splitting and the opening of
the carcass. There was a surprisingly low prevalence of carcass contamination in
the chilling room, which was well below their national average but it was still
markedly higher in the worst slaughterhouse than the cleanest but lower than the
infected lymph nodes of the pigs coming in. What next?
where do we go from here? The study was set up so that Salmonella reduction
targets could be set for pigs regarding serovars with public health
significance, "supported by a cost/benefit analysis". This is difficult when
"there is convincing evidence that some
cases of salmonellosis are
attributable to infection derived from Salmonella infected pigs or products of
pig origin but the population attributable fraction for the EU has not been
estimated". That is, they don't know how important pigs are in the transmission
of Salmonella to man, so how can they calculate a benefit?
be one of the first things that they do find out, with all the thousands of
isolates they have, before they spend any more millions of euros on these
Investigating slaughterhouse best practices might also be
the most cost-efficient way of reducing the incidence of carcass contamination,
which the Danes have shown several years ago.