CASE NOTES
Descriptive Epidemiology of Salmonella Enteritidis outbreak in New South Wales
Catherine Fraser, NSW Department of Primary Industries
Posted Flock & Herd September 2021
Introduction
Historically, the Australian egg industry has been free of Salmonella enteritidis (SE)1. In September 2018, traceback from a human SE cluster not attributable to overseas travel led to the detection of SE in a New South Wales (NSW) poultry flock.
Summary
There have been 17 premises detected with SE within NSW since September 2018, one of which is solely an egg grading facility. Of the 16 premises with poultry, six (38%) had an onsite grading facility and the remaining 10 (62%) premises had their eggs graded off site.
All infected premises link through movements of eggs, egg packaging, people, vehicles or machinery. The time lag between potential introduction of the SE agent and establishment and subsequent detection on farm was approximately 8 - 14 weeks, and up to five months. At this stage rodents have not played a significant role in transmission.
Clinical disease was present in aged birds (70 - 100 weeks) in three (19%) of flocks. There was no clinical disease or increased mortalities in younger birds.
Relevance
Within NSW, SE has expressed itself as a disease with a slow and insidious spread both within and between premises. With minimal clinical signs in poultry flocks and spread via fomites, SE may spread undetected until contaminated eggs enter the food chain and become a human health concern.
A Control Order under the NSW Biosecurity Act 2015 was implemented on 1 August 2019 for all licensed poultry businesses in NSW to increase biosecurity both on farm and at the farm gate. This Control Order was amended on 30 June 2020 to include mandatory Salmonella enteritidis surveillance for all licensed egg layer farms in NSW. The Control Order is current for 2 years from 30 June 2020.
References
- Sergeant ESG, Grimes TM, Jackson CAW, Baldock FC, Whan IF. Salmonella enteritidis surveillance and response options for the Australian egg industry. RIRDC, Barton, A.C.T, 2003