Pigmeat and meat as source of Salmonella and Campylobacter

Comparison of pig meat and other meats as causes of Salmonella and Campylobacter
infectious intestinal disease in man

Author: DGS Burch BVetMed MRCVS
Octagon Services Ltd Copyright © 2002
On-line at: www.pigjournal.co.uk

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 (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) (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
18/30 cases associated with ham as primary or secondary cause. * 10/13 cross contamination, 7/13 inadequate storage, 5/13 infected food handler, 2/13 inadequate heating, 2/13 other faults. *6/13 cross contamination, 5/13 inadequate storage, 6/13 inadequate heating, 0/13 infected food handler, 3/13 other. **1/2 cross contamination. Species not recorded.
Pig meat products (primary causes)	73
Pork (including cooked pork)	47	64%
Ham	22	31%	*11/22	Salmonella	***5/11	S. Typhimurium
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.

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