A print friendly PDF version is available from this Communicable Diseases Intelligence issue's table of contents.

Historical comparisons use notifications by date of onset. All other data are reported using the date the report was received by the health agency.

Introduction

OzFoodNet is a collaborative network of epidemiologists and microbiologists conducting applied epidemiological research into foodborne disease and improving existing surveillance mechanisms for foodborne disease. The Commonwealth Department of Health and Ageing established OzFoodNet in 2000 and the network has had representation on the Communicable Diseases Network Australia (CDNA) since 2001.

This third quarterly report of OzFoodNet summarises the incidence of foodborne disease in the 6 States of Australia and specific foodborne outbreaks identified between July and September 2001. During the third quarter of 2001, Australia experienced an outbreak of Salmonella Stanley. The CDNA requested that OzFoodNet coordinate the national investigation, which identified contaminated peanuts from China as the food vehicle. The investigation also alerted health authorities in Canada and the United Kingdom to human cases of salmonellosis associated with the same brand of peanuts. Salmonella Typhimurium phage type 126 also emerged as a national problem during the quarter. In September 2001, OzFoodNet began a national survey to estimate the incidence of diarrhoeal disease, and a pilot of the national case control study into Campylobacter infections. During this quarter, the Australian Capital Territory joined OzFoodNet and the Northern Territory participated as an observer. Data are only included for the Territories where specified.

Notifications in the third quarter

During the third quarter 2001, OzFoodNet sites reported 4,014 notifications of campylobacteriosis, which represented a 25 per cent increase over the mean for the same quarter for the years 1998 to 2000.¹ The median age of cases ranged between 27 to 33 years old. All States reported that the male to female ratio of cases ranged from 1.1:1.0 to 1.4:1.0. There was one small outbreak of Campylobacter infection in Queensland that was associated with eating duck livers in a restaurant.

OzFoodNet sites reported a total of 1,081 cases of salmonellosis during the third quarter and identified the source of 4 Salmonella outbreaks. As for previous reports, Queensland reported a lower median age of reported cases (9.0 years old) compared to other States (range of medians: 17.0-23.1 years old). OzFoodNet sites reported that Salmonella Typhimurium (phage types 126, and 135), and S. Stanley were the most commonly notified infections during the quarter.

The major feature of Salmonella epidemiology during this quarter was the emergence of Salmonella Typhimurium phage type 126 in jurisdictions across Australia. The National Enteric Pathogen Surveillance Scheme reported that S. Typhimurium 126 was among the five most common infections in five different jurisdictions (Joan Powling, The University of Melbourne, 14 January 2002, personal communication) (Table 1). The South Australian Department of Human Services conducted a case control study of this serovar, which implicated chicken products. There were also concurrent epidemics of this organism in chicken flocks.

Top of pageTable 1. Top five Salmonella infections reported to OzFoodNet sites, July to September 2001, by date of receipt of notification at the Health Department

OzFoodNet Site	Top 5 Salmonella infections	Number of cases
		3rd Qtr 2001	3rd Qtr 2000	Year to date 2001	Total 2000	Ratio*
Queensland	S. Typhimurium 135	22	14	99	83	1.6
	S. Virchow 8	22	18	145	153	1.2
	S. Typhimurium 126	16	0	52	2
	S. Saintpaul	15	23	121	157	0.7
	S. Aberdeen	13	2	69	42	6.5
Hunter	S. Typhimurium 126	4	1	7	3	4.0
	S. Typhimurium 170	2	0	5	1	-
	S. Birkenhead*	1	0	1	9	-
	S. Bovismorbificans 30	1	0	2	0	-
	S. Bredeney	1	0	1	0	-
New South Wales	S. Typhimurium 135	41	20	155	115	2.1
	S. Typhimurium 9	18	8	107	138	2.3
	S. Stanley	14	1	30	8	14.0
	S. Typhimurium 126	14	6	64	56	2.3
	S. Enteritidis 4	12	5	20	19	2.4
South Australia	S. Typhimurium 126	49	1	88	3	49.0
	S. Typhimurium 108	6	2	12	8	3.0
	S. Stanley	5	0	0	6	-
	S. Infantis	4	1	8	12	4.0
	S. Typhimurium 43	4	0	5	0	-
	SS. Typhimurium 12A	4	1	11	9	4.0
Tasmania	S. Mississippi	4	0	90	69	-
	S. Typhimurium 9	1	1	10	21	1.0
	S. Typhimurium 135	1	1	2	5	1.0
	S. Enteritidis 4	1	0	3	5	-
	S. Infantis	1	0	1	4	-
Western Australia	S. Typhimurium 135	16	7	0	68	2.3
	S. Chester	10	1	0	12	10.0
	S. Kiambu	10	0	0	9	-
	S. Stanley	10	0	0	5	-
	S. Typhimurium 4	7	0	0	1	-
Victoria	S. Typhimurium 99	99	95	438	539	1,0
	S. Typhimurium 9	16	9	33	35	1.8
	S. Typhimurium 135	15	17	79	109	0.9
	S. Stanley	11	3	11	11	3.7
	S. Typhimurium 104	12	0	19	0	-

* Ratio of cases for the third quarter 2001 to the third quarter 2000.

The Tasmanian OzFoodNet site continued to report that the most common serovar was Salmonella Mississippi, which is endemic in that State. Queensland reported that the distribution and rates of salmonellosis changed depending on geographical location, with higher rates in the north of the State. Jurisdictions reported an increase in the incidence of Salmonella Stanley between July and September, which was related to the national outbreak.

State health departments received 14 notifications of listeriosis during the third quarter of 2001, five of which were from Western Australia. Median ages for cases not associated with pregnancy ranged from 43 to 83 years. Tasmania reported one maternal-foetal infection during the quarter.

OzFoodNet sites reported seven cases of shiga toxin producing E. coli infections during the quarter; four were from South Australia and three from Queensland. Investigators did not identify any sources and all cases appeared sporadic. The median age of cases were 22 years in South Australia and 7 years in Queensland. The South Australian Health Department was notified of one case of haemolytic uraemic syndrome in a 21-year-old male on holiday from the United Kingdom.

There were 11 notifications of yersiniosis for the third quarter of 2001 (Figure). The Communicable Diseases Network Australia agreed to remove yersiniosis from the list of nationally notifiable disease, but most jurisdictions still receive reports. The decline in yersiniosis has occurred over several years and follows similar trends in other countries. OzFoodNet sites reported that during the quarter there were 86 cases of shigellosis, and 13 cases of typhoid.

Top of pageFigure. Notifications of yersiniosis in OzFoodNet sites, 1998 to September 2001,s by month of onset

Foodborne disease outbreaks

During the third quarter of 2001, OzFoodNet sites reported 17 outbreaks that were potentially related to food (Table 2). These outbreaks affected approximately 244 people, of whom 7 were hospitalised. There were no reported deaths from these outbreaks. Ten outbreaks were associated with meals served at restaurants, and three with takeaway food or catered functions.

Table 2. Outbreaks reported by OzFoodNet sites, July to September 2001

State	Month of Outbreak	Setting	Agent responsible	Number exposed	Number affected	Evidence*	Responsible vehicles
Australia	Jul-Sep	Community	Salmonella Stanley	Unknown	27	D, M	Imported dried peanuts
ACT	Sep	Conference	Probably Norwalk virus	115	25	D	Suspected salad
Hunter	Jul	Restaurant	Unknown	25	10	D	Suspected honey chicken
	Jul	Fast food outlet	Unknown	Unknown	2	D	Suspected takeaway chicken
Qld	Jul	Restaurant	Clostridium perfringens	15	8	S	Beef curry
	Jul	Restaurant	Clostridium perfringens	7	7	D	Unknown
	Jul	Restaurant	Campylobacter	Unknown	2	D, M	Duck liver
	Aug	Community	Cryptosporidiosis	Unknown	6	S, M	Unpasteurised pets milk (cow)
	Jul	Functions x 2	Norwalk virus	90	56	S	Salads, steak sandwiches
SA	Jun	Household	S. Typhimurium 135a	n/a	2	S, M	Home-made Italian sausage
Vic	Jul	Hotel restaurant	S. Typhimurium 99	91+	19	S	Lamb's fry
	Aug	Restaurant	Butterfish diarrhoea	15	4	D	Escolar
	Aug	Restaurant	S. Typhimurium 99	316+	50	S	Eye fillet meal
	Aug	School camp	Unknown (suspect Campylobacter)	27	6	D	Suspected unpasteurised milk
	Sep	Restaurant	Unknown	17	7	D	Unknown
WA	Jul	Restaurant	Unknown	11	6	D	Suspected undercooked turkey
	Sep	Restaurant	Unknown	10	7	D	None identified

* D = Descriptive evidence implicating the suspected vehicle or suggesting foodborne transmission;
S = Statistical association between illness and one or more foods;
M = Microbiological confirmation of agent in the suspect vehicle and cases.

There were three community-wide epidemics occurring during the quarter, two of which crossed State and Territory boundaries. One of these was a small outbreak of cryptosporidiosis associated with unpasteurised pets' milk that was not intended for human consumption.

The Communicable Disease Network Australia requested that OzFoodNet coordinate the national investigation into an outbreak of Salmonella Stanley amongst people of Asian ethnicity. OzFoodNet held national teleconferences of State and Territory investigators to generate hypotheses about the reasons for this national increase. The Victorian Department of Human Services and the Microbiological Diagnostic Unit (MDU) sampled dried peanuts originating from China after 2 cases gave a history of consumption during interviews. MDU identified Salmonella Stanley in the peanuts with a molecular pattern that was indistinguishable from patient isolates. The Australia New Zealand Food Authority coordinated a nation-wide recall of the contaminated product. OzFoodNet sites reported 27 cases of salmonellosis associated with these peanuts. The Australian investigation triggered product recalls and outbreak investigations in Canada and the United Kingdom.²

The South Australian Department of Human Services continued investigations into a State-wide outbreak of Salmonella Typhimurium phage type 126. Since reporting this outbreak in the previous OzFoodNet report other jurisdictions around Australia have identified cases of this emerging infection.¹ South Australian investigators completed a case-control study that showed that illness was associated with consumption of chicken. The Department also identified corroborating evidence for this link, including descriptive epidemiology and microbiological evidence.

This outbreak is one of a number in 2001 that were possibly associated with chicken.^1,3,4 It is concerning that cases of this serovar are now occurring in other Australian States and Territories. It once again raises the difficult question about the role that contaminated chicken plays in the epidemiology of Salmonella and Campylobacter infections in humans in Australia.

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Applied research

In September 2001, the Tasmanian OzFoodNet Site piloted the national Campylobacter case control study. This study aims to examine the risk factors for infection with sporadic Campylobacter infection. Campylobacter is the most common enteric disease reported to health agencies, and is a cause of significant morbidity in Australia. This study will recruit approximately 1,200 cases and 1,200 controls across Australia during the next 12 months. The case control study will use the results of a comparison of 8 Campylobacter typing methods that is being coordinated by the OzFoodNet-Hunter Site and Hunter Area Pathology.

During this quarter, the National Centre for Epidemiology and Population Health started the national OzFoodNet gastroenteritis survey. The aim of this cross-sectional survey is to measure the prevalence of gastrointestinal illness across all States and Territories of Australia. Interviewers use Computer Assisted Telephone Interviews (CATI) to ask respondents about demographic details and whether they have experienced an episode of gastrointestinal disease in the last month. If participants mention that they have had an episode of gastroenteritis, interviewers record symptom details and the patients' use of health services. This study includes residents of the Northern Territory where many people living in remote areas would not have telephone. Despite this, in the month of September Northern Territory residents reported the highest crude proportion of people experiencing gastroenteritis in the previous month, and South Australian residents reported the lowest (Table 3).
Table 3. Unweighted results of the national OzFoodNet gastroenteritis survey during September 2001 showing the proportion of respondents reporting an episode of gastroenteritis in the previous month, and the response rates by jurisdiction

State or Territory	Number of respondents	Proportion with gastro (%)	Response rate (%)
New South Wales*	110	9.3	64
Victoria	93	11.8	64
Tasmania	97	9.3	71
Queensland	89	14.6	62
South Australia	90	8.8	68
Western Australia	83	10.8	65
Northern Territory	68	23.5	63

* Includes an over sample for the Hunter region of New South Wales.

The population survey covers all States and Territories and will run for a year. It will provide important information about the burden of gastrointestinal disease and will supplement information that States and Territories collect about the causes of foodborne illness. OzFoodNet aims to combine these data to learn more about the causes and burden of foodborne illness in Australia.

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Author affiliations

1. The OzFoodNet Working Group is (in alphabetical order): Rosie Ashbolt (Tas), Meredith Caelli (Hunter PHU), Scott Crerar (ANZFA), Craig Dalton (Hunter PHU), Rod Givney (SA), Joy Gregory (Vic), Gillian Hall (NCEPH), Brigid Hardy (AFFA), Geoff Hogg (MDU), Rebecca Hundy (SA), Martyn Kirk (ANZFA), Vanessa Madden (Tas), Ian McKay (DoHA), Lynn Meuleners (WA), Geoff Millard (ACT), David Peacock (NT), Nittita Prasopa-Plaizier (Vic), Paul Roche (Doha), Russell Stafford (Qld), Nola Tomaska (NCEPH), Leanne Unicomb (Hunter PHU), Craig Williams (ANZFA)

Corresponding author: Mr Martyn Kirk, Coordinating Epidemiologist, OzFoodNet, c/o National Public Health Partnership, 589 Collins St, Melbourne 3000, Australia. Telephone: +61 3 9616 1522. Facsimile: +61 3 9616 1500, martyn.kirk@dhs.vic.gov.au.

References

1. The OzFoodNet Working Party. OzFoodNet: Enhancing foodborne disease across Australia: Quarterly report April to June 2001 Commun Dis Intell 2001;25:270-272.

2. Kirk M for the Outbreak Investigation Team. Salmonella enterica serotype Stanley in peanuts. Promed Mail (http://www.promedmail.org), 11 September 2001, Archive Number: 20010911.2189.

3. The OzFoodNet Working Party. OzFoodNet: Enhancing foodborne disease across Australia: Quarterly report January to March 2001 Commun Dis Intell 2001;25:103-106.

4. Tribe I, Cameron AS. Salmonella Zanzibar in rural South Australia. Commun Dis Intell 2001;25:102.


This article was published in Communicable Diseases Intelligence Volume 26, No 1, March 2002