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Introduction

OzFoodNet is a collaborative network conducting applied research into foodborne disease. It was established by the Commonwealth Department of Health and Ageing, formerly the Department of Health and Aged Care.¹ During the second quarter of 2001, OzFoodNet prepared several protocols for national studies investigating the burden and causes of foodborne disease. OzFoodNet epidemiologists assisted with investigations into several outbreaks of foodborne illness, including a major outbreak of Salmonella Bovismorbificans 32 associated with iceberg lettuce, and Australia's first outbreak of multi-drug resistant Salmonella Typhimurium Definitive Type (DT) 104.

This second quarterly report of OzFoodNet summarises the reporting of foodborne disease in the six States of Australia during the second quarter of 2001.² During this time, the Australian Capital Territory and the Northern Territory participated as observers in OzFoodNet, and we have not included data from these jurisdictions unless specified.

Notifications in the second quarter

In this report we have used the date that the health department received notifications, unless specified otherwise.

During the quarter, OzFoodNet sites reported 3,551 notifications of campylobacteriosis (excluding New South Wales). The median ages of cases ranged between 24-32 years. All States reported that the male to female ratio of cases was approximately 1:1 except South Australia (1.4:1). The Tasmanian Health Department reported a large increase in the rate of Campylobacter infections in the northern part of Tasmania, although no source was identified. The South Australian Department of Human Services investigated one point source outbreak of Campylobacter infection associated with a restaurant meal.

OzFoodNet sites reported a total of 1,672 cases of salmonellosis during the second quarter and identified the source of 10 Salmonella outbreaks. The median ages of reported cases in all States ranged from 15-24 years old, except for Queensland where the median age was 9 years. OzFoodNet sites reported that Salmonella Typhimurium (phage types 64, 135 and 126), Virchow (8 and 36var1) and Enteriditis were the most common serovars (Table 1). The majority of these Salmonella Enteriditis infections were acquired overseas.

The following table displays Notifications of new and relapsed cases of tuberculosis, and rates per 100,000 population, Australia, 1986 to 1999, by year. If you are not able to access these data please e-mail cdi.editor@health.gov.au.

Top of pageTable 1. Top five Salmonella infections reported to OzFoodNet sites, April to June 2001, by date of receipt

OzFoodNet site	Top five Salmonella infections, by type	Number of cases
		2nd quarter 2001	2nd quarter 2000	YTD 2001	Total 2000	Ratio1
Queensland	Virchow 8	59	66	123	126	0.89
	Saintpaul	40	90	106	132	0.44
	Bovismorbificans 32	36	0	36	1	-
	Birkenhead	33	21	96	55	1.57
	Typhimurium 126	27	1	35	2	27.0
Hunter	Typhimurium 64	4	3	7	14	1.33
	Typhimurium 44	2	0	5	0	-
	Typhimurium 170	2	0	3	1	-
	Typhimurium 135	1	3	7	10	0.33
	Enteriditis	1	1	1	1	1.00
New South Wales	Typhimurium 135	34	34	25	138	1.00
	Typhimurium 9	29	47	30	115	0.61
	Birkenhead	18	17	12	77	1.05
	Typhimurium 64	17	21	55	53	0.81
	Stanley	10	5	11	56	2.00
South Australia	Typhimurium 126	29	1	74	4	29.00
	Typhimurium 9	14	7	36	28	2.00
	Typhimurium 64	9	4	22	20	2.25
	Typhimurium 108	5	3	6	9	1.70
	Virchow	5	2	15	1	2.50
Tasmania	Mississippi	31	19	86	69	1.60
	Typhimurium 9	5	4	9	21	1.30
	Enteriditis 4	2	3	2	5	0.67
	Enteriditis 1	2	1	2	1	2.00
	Typhimurium 135	2	1	2	5	2.00
Western Australia	Typhimurium 135	5	59	49	68	0.08
	Typhimurium 22	3	2	5	2	1.50
	Typhimurium 4	3	7	18	13	0.43
	Typhimurium 8	3	0	4	1	-
	Bovismorbificans	2	0	7	0	-
Victoria	Typhimurium 9	33	55	89	186	0.60
	Typhimurium 135	20	21	63	71	0.95
	Typhimurium 4	17	2	54	37	8.50
	Virchow 36var1	11	10	20	19	1.10
	Virchow 34	8	18	24	60	0.44

1. Ratio of number of cases reported in second quarter 2001 to second quarter 2000

The Tasmanian OzFoodNet Site reported that Salmonella Mississippi - an endemic serovar in this State - was the most common Salmonella infection for the quarter. Tasmania reported one household cluster of S. Mississippi, although no source was identified. Both Queensland and New South Wales OzFoodNet sites reported that Salmonella Birkenhead was common, which relate to an endemic focus of this serovar in southeast Queensland and northern New South Wales. During the quarter, State and Territory Health Departments commenced investigations into a variety of Salmonella serovars, including: Bovismorbificans (phage types 32 and 14), Muenchen, Typhimurium (phage types 126, 135 and 104) and Virchow (phage type 8).

State health departments received 11 notifications of listeriosis during the second quarter of 2001, which compared to 22 for the same quarter in 2000. Median ages for cases ranged from 38.5 to 70 years. South Australia reported one foetal infection in an infant of 34 weeks gestation. The mother had previously consumed soft cheese. There is little seasonality to notifications of Listeria infection (Figure). Despite the small numbers of cases of listeriosis notified to individual jurisdictions, there is potential for cross-border or national outbreaks.

Figure. Notifications of listeriosis, Australia, 1998 to June 2001, by States and Territories, and month of onset



OzFoodNet sites reported 10 cases of shiga toxin producing E. coli infections during the quarter, with South Australia and Queensland each reporting four cases. Investigators did not identify any sources and all cases appeared sporadic. The median ages ranged from 14 to 71 years.

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Foodborne disease outbreaks

During the second quarter of 2001, OzFoodNet sites reported 16 outbreaks that were potentially related to food (Table 2). These outbreaks affected approximately 224 people, of which 24 were hospitalised and one died. The Victorian Department of Human Services identified helva imported from Turkey, as the source of the first Australian outbreak of multi-drug resistant Salmonella Typhimurium DT 104.* This serovar is a significant problem for countries in the northern hemisphere, due to its propensity to affect many different types of animals, and the antibiotic resistance of the serovar.³ The Queensland Department of Health identified iceberg lettuce that was contaminated during processing as the source of an outbreak of Salmonella Bovismorbificans 32 that affected people across Queensland.

The following table displays Notifications of new and relapsed cases of tuberculosis, and rates per 100,000 population, Australia, 1986 to 1999, by year. If you are not able to access these data please e-mail cdi.editor@health.gov.au.

Table 2. Outbreaks reported by OzFoodNet sites, April to June 2001

State	Month of outbreak	Setting	Agent responsible	Number exposed	Number affected	Responsible vehicles
Hunter	June	Take-away pizza shop	Unknown	Unknown	4	Pizza
	May	Kebab shop	Unknown	Unknown	2	Suspected chicken kebab
	May	Supermarket	Unknown	Unknown	3	Suspected BBQ chicken
	May	Take-away pizza shop	Unknown	Unknown	8	Pizza
Qld	June	Caterer	Suspected Norwalk	14	10	Unknown
	June	Home	Ciguatera	3	3	Barracuda (Sphyraena jello)
	June	Hotel	S. Montevideo	Unknown	8	Unknown
	May	Take away restaurant	S. Bovismorbificans 32	Unknown	36	Commercially processed iceberg lettuce
SA	June	Cafe	S. Zanzibar	Unknown	2	Suspected chicken dish
	June (investigations still continuing)	Community	S. Typhimurium 126	Unknown	44 to end of June; 72 to 10th August 2001	Chicken products
	May	Restaurant	Campylobacter jejuni	13	10	Unknown
Tas	April	Household	S. Mississippi	7	7	Unknown
	April	Household	S. Typhimurium 9	6	6	Suspected duck eggs
Vic	April	School Camp	S. Typhimurium 9	55	29	Unknown
	June	Community	S. Typhimurium DT104	Unknown	23 (20 Vic; 2 NSW;1 Qld)	Turkish Helva
WA	June	Restaurant	S. Typhimurium 64	~40	29	Fried ice cream

Applied research

The OzFoodNet collaboration has achieved some important goals during the first six months of 2001, which included:

• development of a National survey of diarrhoeal disease through the National Centre for Epidemiology and Population Health;
• development of protocols for four national case control studies to examine risk factors for campylobacteriosis, listeriosis, Salmonella Enteriditis, and shiga-toxin producing E. coli;
• development of a national outbreak register for foodborne disease;
• communicating about clusters of foodborne diseases, through a fortnightly cluster report;
• comparing molecular typing methods for Campylobacter;
• development of a national survey of pathology laboratories;
• assisting with the investigation of several important clusters and outbreaks of foodborne disease that have crossed jurisdictional boundaries;
• communication with international agencies involved in similar international work; and
• formation of an important forum for discussing issues relating to foodborne disease.

There are many important areas of foodborne disease surveillance, which OzFoodNet cannot adequately address in this first phase of work. Some examples of this further work include: estimating the cost of foodborne disease, determining the fraction of foodborne disease that is notified to health authorities, novel means of detecting outbreaks, risk factors for other foodborne pathogens, etc. OzFoodNet is currently developing a paper on the potential future of ongoing collaborative work to improve our understanding of foodborne disease.

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Author affiliations

1. Corresponding author: Mr Martyn Kirk, Coordinating Epidemiologist, OzFoodNet, c/o National Public Health Partnership, Level 12, 589 Collins Street, Melbourne Victoria, 3000 Telephone +61 3 9616 1522, E-mail Martyn.Kirk@dhs.vic.gov.au

The full membership of the OzFoodNet Working Group is listed at the end of this report.

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 (DHA), Lynn Meuleners (WA), Geoff Millard (ACT), David Peacock (NT), Nittita Prasopa-Plaizier (Vic), Paul Roche (DHA), Russell Stafford (Qld), Nola Tomaska (NCEPH), Leanne Unicomb (Hunter PHU), Craig Williams (ANZFA)

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References

1. Kirk M for the OzFoodNet Working Party. OzFoodNet: Enhancing Foodborne Disease Across Australia: Quarterly Report January - March 2001 Commun Dis Intell 2001;25: 103-106.

2. O'Grady K, Powling J, Tan A, Vulcanis M, Lightfoot D, Gregory J, et al. Salmonella Typhimurium Dt104 - Australia, Europe. ProMed Mail, 22 August 2001, www.promedmail.org (Accessed 12 November 2001).

3. Crerar SK, Nicholls TJ, Barton MD. Multi-resistant Salmonella Typhimurium DT104 - implications for animal industries and the veterinary profession. Aust Vet J1999;77:170-1.


This article was published in Communicable Diseases Intelligence Volume 25, No 4, November 2001.