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Foodborne disease across Australia, Oct – Dec 2004

OzFoodNet is a national network of epidemiologists working with State, Territory governments and other organisations to investigate foodborne disease in Australia. During 2004, OzFoodNet strengthened surveillance of these very common diseases.

For many foodborne diseases, control measures are difficult to implement. In the July 2004 issue of Food Safety & Hygiene, we discussed outbreaks of Norovirus due to oyster meat imported from Japan. Since 2002, there has been seven outbreaks of gastroenteritis attributed to these imported products. One of these outbreaks occurred even though the oyster meat was cooked, which highlighted the difficulty of ensuring that these products were safe. In 2004, the importation of these raw oysters from certain geographic regions was restricted by the Australian Quarantine and Inspection Service (AQIS) unless they could be demonstrated safe for consumers.

During the fourth quarter of 2004, OzFoodNet sites reported 26 outbreaks of foodborne disease affecting approximately 458 people. Nineteen people were hospitalised as part of these outbreaks and there were no fatalities. Six of the outbreaks were due to Salmonella, three due to Noroviruses and two due to Campylobacter. In the majority of these outbreaks (22/26), investigators were unable to identify a food vehicle. Over half of the outbreaks (14) resulted from food prepared in restaurants or by commercial caterers.

There was one outbreak of histamine poisoning where a commercial caterer served rudderfish. Rudderfish is often marketed incorrectly, and should be sold as Escolar. In this instance, the Health Department was unable to collect fish samples to identify the species. Rudderfish and Escolar (see FDA Regulatory Fish Encyclopaedia: vm.cfsan.fda.gov/~frf/rfe0ec.html), haves caused several outbreaks of histamine poisoning. Histamine compounds build up in the flesh of certain fish species (particularly of the scombroid family) due to the activity of spoilage bacteria. The symptoms of histamine poisoning usually occur within two hours of eating the fish and include numbness of the mouth and tongue, flushing, nausea, vomiting, sweating and diarrhoea. Escolar served as Rudderfish have also been known to cause keriorrhoea (orange oily stools) due to the high concentration of indigestible wax esters in the flesh of the fish (see Food Safety & Hygiene, March 2003). These fish are not suitable for use in food service industries because of the problems of histamine poisoning and indigestible wax esters.

There was also a small outbreak of illness amongst recreational fishermen in Victoria. The illness consisted of gastroenteritis and neurological symptoms following consumption of Redfin, although the exact cause was never identified.

It is important to recognise that many foodborne infections are not part of recognised outbreaks. The National Notifiable Disease Surveillance System recorded 6,927 cases of eleven diseases that are potentially foodborne. These common infections include: campylobacteriosis, salmonellosis, listeriosis and yersiniosis. Reports for several of these diseases were higher than for the same time period in 2003, including infections of Campylobacter (14 percent increase) and Salmonella (21 percent increase).

Improving investigation

In October 2004, OzFoodNet trialled NetEpi (www.health.nsw.gov.au/public-health/epi/open_source_tools.html), a web-based database for capturing patient information during community-wide outbreaks. To test the system, OzFoodNet epidemiologists in State and Territory health departments entered information about patients for a mock outbreak. The mock scenario was a fictitious outbreak of Salmonella Mordor involving wizards, elves, ents and hobbits attending a birthday party in Tasmania! The trial showed that web-based databases are excellent for collecting epidemiological data about individuals affected by an outbreak occurring over a wide geographic area. NetEpi was a useful tool to capture this information and will be used in the future.

In 2005, OzFoodNet will further improve coordination arrangements for outbreaks of foodborne disease. Two initiatives that will assist this are the development of guidelines for the investigation of multi-jurisdictional outbreaks, and a workshop to train people conducting epidemiological studies during outbreaks. This article was contributed by OzFoodNet. For more information contact:
Martyn Kirk, Coordinating Epidemiologist, OzFoodNet,
Tel: +61 2 6289 9010, martyn.kirk@health.gov.au