Comparison of Pigmeat and other Meats as Causes of Salmonella and Campylobacter
Infectious Intestinal Disease in Man
by
David G S Burch BVetMed MRCVS
Copyright © 2002 - Octagon Services Ltd
 

Part 1. Salmonella isolations from reported incidents - species comparison (%)
The 10 most common species of Salmonella isolated in man in 1996 compared with 2000 and for the different species of animals:

 
Species Man '96 (1) Man '00(2) Pig '96 (2) Pig '00 Cattle '96 Cattle '00 Sheep '96 Sheep '00 Chicken '96 Chicken '00 Turkey '96 Turkey '00
S. Enteritidis 63.1 57.4 1 0 0.9 0.9 0.4 0 19.1 0.9 0.9 0
S.Typhimurium 19.4 18 58.9 76.7 59.5 23.5 36.3 15.6 9.2 3.3 29.5 11.9
S. Virchow 4.2 2 0 0 0.5 0.1 0 0 7.4 2.5 0 0
S. Hadar 2.1 2.2 0 0 0.3 0 0 0 0.4 3.3 1.3 2.8
S. Newport 0.7 1 0.5 0 1.1 0.8 0 0.5 3.1 1.1 23.9 8.3
S. Heidelberg 0.7 NR 0 0.6 0.1 0.2 0 0 0.2 5.4 0.4 3.2
S. Infantis 0.7 1.1 0.3 0.3 0.3 0.2 0 0 5.9 0 0 0
S. Indiana 0.6 NR 0 0.3 0.5 0 0 1 2.3 0.7 12.8 3.6
S. Agona 0.5 1 0 0.6 0.4 0.5 0.4 1.5 1 1.5 0 11.9
S. Braenderup 0.4 NR 0 0 0 0.1 0 0 0.8 0 0 0.8
Sub-total 92.4 82.7 60.7 78.5 63.6 26.3 37.1 18.6 49.4 18.7 68.8 42.5
Others 7.6 17.3 39.3 21.5 36.4 73.7 62.9 81.4 50.6 81.3 31.2 57.5
Total  100 100 100 100 100 100 100 100 100 100 100 100
No. 30075 16556 392 313 1699 1006 238 192 1016 1168 234 253
NR - not reported
Carcase contamination with salmonella in the UK (2,3):
Faecal carriage (%) (2) 23 0.2 0.1
Carcase swabs (%) 5.3 (2.1% S. Typhimurium)
Food samples (%) (3) 8 Raw sausage 33 (Chilled)
41 (frozen)
References:
1. Resistance to antibiotics and other antimicrobial agents report (1998) House of Lords Select Committee on Science and Technology
Memorandum by the Public Health Service Section 7.3 Salmonella, pp. 56-60.
2. Salmonella in livestock production in GB, 2000 (2001) Veterinary Laboratories Agency, DEFRA.
3. Bell, C. and Kyriakides, A. (2002) Salmonella - a practical approach to the organism and its control in food Blackwell Sciences Ltd, Oxford, UK, pp18-19.

Conclusions:
1. Pigs have a very low isolation rate of S. Enteritidis, which is the major cause of salmonella infections in man but salmonella has been isolated from 5% of carcases.
2. Chickens had the most similar pattern of infection to man, but this has changed dramatically by 2000 with fewer reported S. Enteritidis PT4 incidents in 2000.
3. S. Typhimurium is found in chickens but was the most common in all the other species but accounted for only 19% of human cases.
4. Many of the less common isolates (usually exotics) have a variable reporting rate in man and animals.

 

Part 2. Comparison of isolation patterns of Campylobacter species in man and animals (%) (4 & 5)

 
OSL Database (4) Man Pig Cattle Sheep Chicken
C. jejuni 89 7 - - 85
C. coli 11 93 - - 15
No. 2055 1136 - - 316
UK data (5)
C. jejuni - 1 92 45 -
C. coli - 99 8 55 -
No. 733 108 143
References:
4. Octagon Services Ltd, International Database.
5. Teale,C. J. and others. (2002) Veterinary surveillance for antimicrobial resistance in Campylobacter, Enterococci and other bacteria. Proceedings of conference ' Surveillance for Antimicrobial Resistance in Domestic Livestock and the Risk to Public Health' 12th February, 2002.

Conclusions:
1. C. jejuni is the dominant cause of food poisoning and most frequent isolate found in man, whereas in the pig C. coli is the dominant isolate.
2. Chickens and cattle have a similar isolation pattern to man but sheep is approximately half and half.
 

Part 3. Infectious intestinal disease in man associated with meats 1992-99 (8 years) (Refs: 6 & 7)
 

Red Meats Poultry
No of reported cases (all) 4604 4604
Attributed to food borne causes (all) 1426 1426
Attributed to red meat / poultry 228 16.0% 273 19.1%
Pig meat Beef Lamb Chicken Turkey Duck
Attributed to types of meat 73 77 25 196 60 4
% foodborne diseases 5.1 5.4 1.8 13.7 4.2 0.3
Major organisms:
Salmonella outbreaks 35* 17 7 125 25 3
S. Enteritidis 13** 8 0 72 15 2
S. Enteritidis PT4 10 8 0 64 12 1
S. Typhimurium 13*** 6 3 15 5 1
S. Virchow 0 0 0 9 0 0
Other salmonella 9 3 4 19 5 0
Campylobacter spp. 2**** 0 0 14 1 1
Clostridium perfringens 15 50 17 31 26 0
E. coli (VTEC O157) 2 1 0 2 0 0
Links: Overall Overall
Linked to commercial catering (restaurants etc.) 104 149
% linked to commercial catering 45.6 54.6
Linked to residential setting (old peoples homes etc.) 37 22
% linked to residential settings 16.2 8.3
Linked to domestic setting (home) 7 19 55
% linked to domestic setting 9.6 8.3 20.7
Contributing factors: Overall Overall
Infected food handler 16 5 0 29 17 6 0 24
Inadequate heat treatment 24 33 9 84 89 29 1 120
Cross contamination 33 15 4 79 77 19 4 105
Inappopriate storage 29 37 14 104 81 33 2 119
Other faults 8 10 2 25 10 4 0 14
 
*11/35 salmonella cases associated with ham as a primary cause.
** S. Enteritidis 10/13 cross contamination, 7/13 inadequate storage, 5/13 infected food handler, 2/13 inadequate heating, 2/13 other faults.
*** S. Typhimurium 6/13 cross contamination, 5/13 inadequate storage, 6/13 inadequate heating, 0/13 infected food handler, 3/13 other.
**** Campylobacter spp. 1/2 cross contamination. Species not recorded.
Pig meat products
(as primary cause)		 73
Pork (including cooked pork products) 47 64% *23/47 Salmonella **10/23 S.Enteritidis ***8/23 S.Typhimurium 5/23 other salmonella
Ham 22 31% *11/22 Salmonella *2/11 S.Enteritidis ***5/11 S.Typhimurium 5/11 other salmonella
Bacon 4 6% *1/4 Salmonella **1/1 S.Enteritidis
References:
6. Smerdon, W.J., and others (2001) General outbreaks of infectious intestinal disease linked with red meat, England and Wales, 1992-1999, Communicable Disease and Public Health, 4, 4, 259-267.
7. Kessel, A. S. and others (2001) General outbreaks of infectious intestinal disease linked with poultry, England and Wales, 1992-1999, Communicable Disease and Public Health, 4, 3, 171-177.

Conclusions:
1. Red meats have been associated with 16% of reported infectious intestinal disease in man and poultry 19.1%.
2. Pig meat was linked with only 5.1% of cases in comparison with poultry at 13.7%
3. Salmonella was associated with pig meat( 35/73) but all of the S. Enteritidis outbreaks (13/35) could be related to cross-contamination or other faults in hygiene or storage or infected food handlers.
4. Some outbreaks of S. Typhimurium (3/13), the commonest isolate from pigs and their carcasses, could not be linked to poor handling etc. and may be directly meat associated.
5. The 3 S. Typhimurium cases with no links were all from ham or cooked pork, which makes one suspicious that they had been contaminated in some way.
6. Eight of the eleven salmonella outbreaks involving ham were linked to cross contamination and 1 of the bacon cases involving salmonella was also from cross contamination.
7. The risk of campylobacter infections being transmitted to man from pig meat appear to be very low (2 cases); one was linked to cross contamination but no species data was reported.
8. Overall, once the effects of cross contamination and poor storage factors etc are removed, pig meat would appear to pose a relatively low risk as a source of food poisoning to man.
The low percentage of outbreaks ( 9.6%, 7/73) involving preparation in the home, where more care is taken, in comparison with nearly 50% in commercial premises, would appear to confirm this.
Cross contamination of uncooked and cooked products in particular, is a risk for pork-based products but improved handling, hygiene and cooking could substantially reduce or even eliminate it.

 

Copyright © Octagon Services Ltd   2002

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