OzFoodNet: enhancing foodborne disease surveillance across Australia. Quarterly report January to March 2001

This article published in Communicable Diseases Intelligence Volume 25, No 3, August 2001 contains the quarterly report for OzFoodNet, which aims to enhance the existing surveillance mechanisms for foodborne disease across Australia.

Page last updated: 20 September 2001

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


Martyn Kirk for the OzFoodNet Working Group


Introduction

In the latter part of 2000 the Commonwealth Department of Health and Aged Care established and funded a collaborative network - coined OzFoodNet - to enhance the existing surveillance mechanisms for foodborne disease across Australia.

The aims of OzFoodNet are to:
  1. estimate the incidence of foodborne disease in Australia;
  2. learn more about the causes and determinants of foodborne disease;
  3. identify risky practices associated with food handling and preparation; and
  4. train foodborne disease epidemiologists.
The work of OzFoodNet will improve surveillance of foodborne disease across Australia. Collaborators of OzFoodNet include State health authorities, the National Centre for Epidemiology and Population Health (NCEPH), the Public Health Laboratory Network (PHLN), Territory health departments, and national government agencies.

State health authorities have employed epidemiologists to enhance foodborne disease surveillance and conduct applied research into foodborne disease. Western Australia, South Australia, Tasmania, Queensland and Victoria are enhancing surveillance across the whole State. New South Wales is concentrating efforts on the Hunter region although comparative data for the rest of the State area were supplied where available.

Notifications in the first quarter 2001

In the first quarter of 2001, Campylobacter was the most commonly notified enteric pathogen, with 3056 cases reported to all OzFoodNet sites, except New South Wales, where campylobacteriosis is not a notifiable disease. Despite the large number of cases, there was only one cluster investigated in OzFoodNet sites for the period.

OzFoodNet sites reported 2115 cases of salmonellosis (529 from New South Wales) and 10 outbreaks. Notifications of salmonellosis for the first quarter of 2001 were increased in the Tasmania (19.0%), and in the Hunter Public Health Unit (Hunter PHU) (15.8%), when compared with the three-year mean for the same quarter for 1998-2000. Although there was also a 37.7 per cent increase in Western Australia, this reflected a change in the notifications system there, whereby laboratory notifications were counted for the first time only from the beginning of 2000. Notifications of Salmonella infections from the States of South Australia (-53.4%), Queensland (-18.8%), Victoria (-12.0%), and New South Wales (-9.5%) were decreased compared to three-year mean values (Figure).

Figure. Notifications of Salmonella infections to OzFoodNet sites, January 1998 to March 2001, by date of onset

Figure. Notifications of Salmonella infections to OzFoodNet sites, January 1998 to March 2001, by date of onset

Salmonella Typhimurium Phage Type 135 was one of the most common serovars in OzFoodNet sites (Table 1). It was represented in the top 5 serovars of all sites, except for Tasmania. Some States distinguished Typhimurium 135 into variant 135a, although reference laboratories are currently clarifying the sub-typing of this serovar. In Tasmania, the predominant serovar reported during the quarter was S. Mississippi (56/71 cases) - a serovar endemic to this State. The incidence of S. Mississippi in Tasmania was similar to previous years and there was no obvious geographical clustering. Data on Salmonella serovars were not available for samples from Western Australia at the time of writing this report.

Top of pageTable 1. Top five serovar of Salmonella notified to OzFoodNet sites, January to March 2001, by date of onset

State
  First quarter 2000 Second quarter 2000 Total 2000 % change
New South Wales Typhimurium 135
52
28
121
85.7
Typhimurium 135a
28
3
13
833.3
Typhimurium 9
38
44
136
-13.6
Typhimurium 64
31
33
76
-6.1
Birkenhead
26
23
76
13.0
Hunter PHU Typhimurium 135a
7
0
0
 
Typhimurium 135
5
2
10
150.0
Typhimurium 64
3
5
13
-40.0
Typhimurium 9
3
2
3
50.0
Typhimurium 44
2
0
0
 
Queensland Birkenhead
62
35
97
77.1
Saintpaul
61
44
185
38.6
Virchow 8
48
66
175
-27.3
Typhimurium 135
42
57
127
-26.3
Aberdeen
27
25
58
8.0
South Australia Typhimurium 9
19
8
28
137.5
Typhimurium 135
19
1
3
1800.0
Typhimurium 126
15
0
4
 
Typhimurium 64
13
4
20
225.0
Chester
9
6
18
50.0
Tasmania Mississippi
56
36
73
55.6
Typhimurium 9
3
7
22
-57.1
Bovismorbificans
1
0
1
 
Enteriditis 1
1
1
1
0.0
Muenchen
1
0
0
 
Victoria1 Typhimurium 9
51
58
178
-12.1
Typhimurium 135
43
23
68
87.0
Typhimurium 4
37
7
38
428.6
Virchow 34
16
37
60
-56.8
Typhimurium 170
15
9
36
66.7

1. Victorian data reported by date of receipt at the Victorian Department of Human Services.


OzFoodNet sites reported 22 cases of listeriosis with reported onset of symptoms in the first quarter of 2001. The highest number of cases was reported from Queensland (8   cases), followed by Victoria (6 cases), and New South Wales (5 cases). The majority of these cases were reported in older males who were immunocompromised. The median age of cases varied between 63 and 83 years. None of the cases in Queensland involved maternal-foetal infections.

South Australia recorded 77.3 per cent (17/22) of cases of Shiga toxin producing E. Coli (STEC) from OzFoodNet sites during the first quarter of 2001. The median age of these South Australian cases was 32.5 years (range 0-87 years), and the male to female ratio was 1:1. South Australian pathology laboratories intensively screen faeces containing blood for the presence of a gene that encodes for production of shiga toxin. Other States do not conduct similar intensive screening, and detecting toxin producing E. coli requires special culture media or the use of nucleic acid detection methods. These factors account for the relatively higher number of reports from South Australia.

The only other OzFoodNet sites to report STEC cases were Victoria (3 cases), and Queensland (2 cases). Despite the high number of cases reported from South Australia relative to other States, the total number reported in South Australia was decreased in the first quarter of 2001 compared to previous years.

There were 3 reports of haemolytic uraemic syndrome during the first quarter of 2001. Two of these were from Queensland and one was from Victoria. E. coli O111 was identified in one of these cases, but no toxigenic E. coli were isolated from the other 2 cases.

Top of page

Foodborne disease outbreaks

During the quarter, OzFoodNet sites reported 27 outbreaks that were potentially related to food. These outbreaks affected approximately 402 people and a total of 28 people were hospitalised (Table 2). Some of these outbreaks were associated with previously recognised high-risk foods or food preparations and should have been preventable. An example of this was a small family cluster of rudderfish diarrhoea that occurred in the Hunter area of New South Wales. Similar outbreaks of rudderfish diarrhoea have previously occurred in Victoria and South Australia.

Table 2. Outbreaks reported by OzFoodNet sites, first quarter 2001

State
Month
Setting
Agent responsible
No. exposed
No. affected
Responsible vehicles
Vic Jan Function S. Typhimurium 170 30 14 Beef product suspected
Jan Restaurant Norwalk 12 9 Unknown
Feb Restaurant Unknown 9 5 Unknown
Feb Restaurant Norwalk 159 65 Possible sausages
Feb Restaurant Unknown (suspected Norwalk) 56 24 Unknown
Mar Home Ciguatera toxin 17 13 Coral Trout
Mar Hotel Unknown 36 9 Possible cheese platter, mushroom risotto, Thai prawns or combination
Mar Restaurant Unknown 18 14 Unknown
SA Dec 00- Jan 01 Restaurant S. Typhimurium 29   8 Consumption of prepared food at the restaurant
Nov 00-Jan 20   Rotavirus in one faecal specimen   11  
Mar   S. Typhimurium 126   9 Custard fruit tart
Jan   S. Typhimurium 185   5  
Mar Aged care S. Typhimurium 135 38 17 Raw egg (served in mince and potato pie and rice pudding)
WA Mar Remote mine S. Typhimurium untyped ~300 29 Probably bore water supply
Feb-Mar Detention centre S. Wandsworth ~1000 501 Unknown
Tas Feb   Unknown 10 9 Unknown
Qld Jan Home Ciguatera 14 14 Spanish mackerel
Jan Home Ciguatera 2 2 Spotted Mackerel
Jan Restaurant C. perfringens 25 9 Reef and Beef (possible sauce)
Jan Camp (health retreat) Unknown 141 87 Drinking water
Feb Restaurant Histamine poisoning 4 4 Mahi Mahi
Feb Aged care facility Unknown Unknown 19 Unknown
Feb Wedding Unknown 110 6 Unknown
Feb Aged care facility S. Heidelberg PT 1 Unknown 12 Suspected raw egg drink
Mar Aged care facility S. Muenchen Unknown 3 Unknown
Mar Caterer S. Virchow PT 8 Unknown 2 Chicken
Mar Takeaway C. jejuni Unknown 3 Chicken kebabs

1. All cases in this outbreak were asymptomatic.


During the quarter, the Queensland OzFoodNet site reported a small cluster of 3 cases of Campylobacter infection that was associated with a chicken kebab shop. This is the third small outbreak of Campylobacter associated with take-away kebab shops in the last 2 years. These infections are easily prevented providing proprietors cook the meat thoroughly, monitor the internal temperature of the meat, and handle foods correctly.

There were 2 outbreaks of salmonellosis associated with raw or undercooked eggs served to residents of aged care facilities during the quarter. One of these outbreaks was due to Salmonella Heidelberg 1 (Queensland), and the other to Salmonella Typhimurium 135 (South Australia). There is a high risk of Salmonella infection associated with the consumption of raw eggs, which should not be served to elderly people.

Top of page

Surveillance improvements and applied research

The work of OzFoodNet during the quarter revealed several areas where surveillance and control activities for foodborne disease need improvement. These have included differences between States in the case definition for listeriosis, and delays in communicating Salmonella typing information. OzFoodNet will work with stakeholders, such as State and Territory health departments, the Communicable Diseases Network Australia (CDNA) and industry groups, to effect improvements.

OzFoodNet epidemiologists in each site have developed plans for studies to further our knowledge about foodborne disease in Australia. These studies include:
  • a national survey of diarrhoeal prevalence;
  • four case control studies into risk factors for infections due to: Campylobacter, Salmonella Enteriditis and other locally-important serovars, Listeria, and STEC;
  • a census of pathology laboratories for faecal testing practices;
  • a register for foodborne outbreaks;
  • laboratory sub-typing projects on Campylobacter;
  • a retrospective review of foodborne disease across Australia; and
  • enhanced surveillance through laboratories and general practitioners.
It is expected that these studies will commence within the next three months.

OzFoodNet has only recently been established, but has developed into an extensive network of foodborne disease specialists. This has the potential to benefit investigations of foodborne disease that cross State and Territory boundaries. OzFoodNet sites will provide an estimate of the incidence of foodborne disease in Australia, and will work to improve investigation and control efforts.

OzFoodNet represents a significant investment in applied research into foodborne disease. It is important for the results of this work to become incorporated into policy formulation. The results of analytical studies will provide a useful insight into the occurrences of foodborne disease in Australia.

The OzFoodNet Working Group is (in alphabetical order):

Rosie Ashbolt (Tas), Louise Carter (ACT), 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), Martyn Kirk (ANZFA), Vanessa Madden (Tas), Ian McKay (DHAC), David Peacock (NT), Nittita Prasopa-Plaizier (Vic), Paul Roche (DHAC), Russell Stafford (Qld), Elenor Sullivan (WA), Nola Tomaska (NCEPH), Tony Watson (WA), Leanne Unicomb (Hunter PHU)

Footnotes

* Totals for foodborne disease in this report differ from those reported for the same period to the National Notifiable Diseases Surveillance System. This report analysed cases by date of report and included cases with a disease onset date in 2000 and a date of report in the first quarter 2001 unless specified otherwise.

† The three-year mean value for South Australia was skewed by the large number of cases in a Salmonella Typhimurium 135a outbreak associated with contaminated orange juice in March 1999.

Author affiliation

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 above.


This article was published in Communicable Diseases Intelligence Volume 25, No 3, August 2001.

Communicable Diseases Intelligence subscriptions

Sign-up to email updates: Subscribe Now

This issue - Vol 25, No 3, August 2001