Salmonella Enteritidis (SE) is a bacteria that can infect poultry and other animals. It can also infect humans usually from eating contaminated food, causing gastroenteritis and a range of other potentially serious health effects.
SE is present and regarded as endemic in many overseas countries where there is production of chicken eggs. This particular type of Salmonella bacteria was previously considered to be largely absent from the Australian egg industry. Recent foodborne outbreaks in humans and detections of SE on a number of Australian egg farms has therefore lead to major concerns within health, agriculture, and food authorities and the Australian egg industry at a national level.
Why SE is a problem
The most common source of SE for human infection is chicken eggs. SE bacteria can live in the reproductive tract of an infected chicken and enter the egg when it is formed, which other types of Salmonella do not usually do. This means that when the egg is laid the bacteria are already inside the egg and pose a risk to anyone who eats that egg.
Chickens infected with SE usually do not show any signs of illness and there is no visible signs that an egg has SE bacteria inside it. Because eggs are often used in food products raw or only lightly cooked, this does not effectively kill the bacteria.
SE infection in people can cause very severe gastroenteritis and other serious health complications, which often requires treatment in hospital.
The SE situation interstate
Health, agriculture and food authorities in New South Wales (NSW) and Victoria are responding to cases of human infection with SE, which has been linked to infection with SE on eggs farms in these states.
Further information about the NSW and Victorian SE outbreak can be found on the NSW Department of Primary Industries Salmonella Enteritidis page.
The SE situation in South Australia
Testing occurs on poultry farms in South Australia, monitoring for the presence of all types of Salmonella bacteria.
Human cases of infection with any type of Salmonella are notifiable to and are followed up by health authorities to determine where the infection came from.
SE has never been detected in poultry in South Australia.
Reduce the risk of SE on your farm
The most common way for SE to spread between farms is via movement of contaminated eggs and their packaging. You should not bring eggs onto your farm from any supplier that cannot provide you with details on the Salmonella status of their flock.
Exercise extreme caution if bringing eggs into South Australia from NSW, given the current outbreak of SE and the number of affected properties in that state. Biosecurity SA advises to never reuse any of the egg fillers from another farm.
Know the status of your suppliers
All movements onto your farm pose a risk of bringing SE onto the farm and infecting your flock. You need to be vigilant in investigating the Salmonella status of all of your suppliers.
Chicks and pullets should only be purchased from flocks with negative test results for SE. Feed should be purchased from a mill that regularly monitors for the presence of Salmonella.
All suppliers should be able to provide you with documentation as to how they manage the risk of Salmonella. This allows you to make a decision as to whether these measures are appropriate for maintaining the biosecurity standards and minimising the risk to your farm.
National SE Monitoring and Accreditation Program
The National Salmonella Enteritidis Monitoring and Accreditation Program is available to all commercial egg producers in Australia. This provides evidence that the flock has been tested for SE and the test results were negative.
Egg producers accredited under this program should be able to share their test results with you, to provide assurance that they are monitoring for the presence of SE.
More information about the National SE Monitoring and Accreditation Program is available on the NSW Department of Primary Industries website.
The only way to effectively minimise the risk of SE entering your farm is to have a very high standard of biosecurity practices in place at all times. All farms should have a documented biosecurity plan in place. The highest risk farms for SE are those with multi-age production systems.
Rodent and insect control
SE persists in the environment for long periods of time. Wild and domestic animals, insects and rodents accessing poultry sheds can spread SE. All farms should have a vermin control program in place. Rodenticide and insecticides must be used according to label instructions to comply with the Australian Pesticides and Veterinary Medicines Authority (APVMA) requirements.
Any vehicles or equipment moving between farms or flocks can potentially spread SE bacteria. Only essential vehicles and equipment should be allowed access to your farm. All vehicles and equipment should be thoroughly cleaned and disinfected both inside and outside before entering another property.
This includes materials such as fillers and pallets. These should be either new or disinfected, otherwise they should not be brought onto your farm, as they pose a risk of spreading SE between farms.
People can also spread SE, either if they themselves are infected with the bacteria, or if their clothing, boots or other items are contaminated. Farm workers and visitors should follow appropriate personal hygiene measures. They should not have contact with poultry at home or on other farms of unknown disease status. If they have recently travelled overseas, appropriate biosecurity measures should be undertaken before they return to work on farm. If they have had contact with poultry or poultry facilities overseas, it should be at least a week until they return to working on the farm.
Any persons with gastrointestinal symptoms such as diarrhoea should not work on the farm until their symptoms have resolved. This is of particular concern for people returning from overseas with gastrointestinal symptoms.
Staff working on the grading floor should ideally not be entering sheds, particularly if they are handling eggs from multiple farms.
Visitors to the farm should be kept to a minimum and the risk each visitor poses determined before they enter the farm, particularly taking into account contact with other poultry or poultry facilities. Clean, sanitised clothing and footwear should be provided on farm for all workers and visitors.
Live animals and animal products
Movement of eggs and live birds poses a risk of spreading SE. See ‘Egg movements’ and ‘Know the status of your suppliers’ above, for ways to minimise the risk.
Keep adequate records
All biosecurity practices on your farm should be auditable, meaning that you should be able to prove that they are undertaken by having standard operating procedures in place, and keeping documents and records.
All movements of vehicles, equipment, people, live birds and eggs onto and off the property should be recorded, so that if any problems are encountered you can easily trace back to where it may have come from.
Vaccination for SE
Vaccines are available against Salmonella Typhimurium (ST). There is currently no commercial vaccine available in Australia for Salmonella Enteritidis.
ST vaccination may provide some cross-protection against SE, but research has shown that vaccination alone is not an effective control strategy for Salmonella to prevent infection in birds or to prevent human infections. Vaccination does not prevent infection of birds with Salmonella.
It is critical that even if vaccination is used, high standards of biosecurity are in place to effectively minimise the risk of entry and spread of SE.
Reporting of SE
Salmonella Enteritidis is a notifiable disease and therefore must be reported to Biosecurity South Australia.
If you have any reason to suspect your flock may be infected with SE, or you have observed any unexplained increase in mortality or disease in your flock, please contact the Emergency Animal Disease Hotline on 1800 675 888.
Phone: (08) 8207 7900