The Food Safety Authority of Ireland says that procedures put in place to control Salmonella in ducks and duck eggs are working, according to the National Salmonella, Shigella and Listeria Reference Laboratory (NSSLRL). In its Annual Report for 2011, the laboratory reports a decrease in the number of cases of illness caused by a particular strain of Salmonella
which has been linked to duck eggs (S. Typhimurium DT8). Because duck eggs can occasionally contain Salmonella, they must not be eaten raw, but fully cooked until the yolk and white are solid. 

Sometimes, subtyping can actually detect outbreaks.  In 2009, the NSSLRL noticed an increase in cases of illness caused by a particular strain of S. Typhimurium (phage type DT8) and alerted public health colleagues to the possibility of an outbreak.  Over 30 cases were detected and investigations by the Outbreak Control Team pointed to the consumption of duck eggs as the source. 

In order to control the outbreak, consumers were advised not to eat raw or undercooked duck eggs and to handle them hygienically.  Also, new legislation setting down a legal basis for the control of Salmonella in ducks and duck eggs was introduced (S.I. No 565 of 2010).  This legislation requires anyone keeping ducks (even a small ‘backyard’ flock) to register with the Department of Agriculture, Food and the Marine (DAFM).  Also, anyone selling even small quantities of duck eggs must put in place a biosecurity plan to prevent Salmonella entering their flock and spreading.  Guidelines are available on DAFM’s website at: www.agriculture.gov.ie/farmingsectors/poultry.

According to the NSSLRL, these control measures have worked.  The number of cases of human illness caused by S. Typhimurium DT8 has dropped from 28 in 2010 to nine in 2011.

Salmonella infection is a notifiable disease in Ireland.  All cases diagnosed by doctors or clinical laboratories must be notified to the Health Protection Surveillance Centre (HPSC), which manages the surveillance of infectious diseases in Ireland.  The HPSC provisionally reported 314 cases of Salmonella infection in 2011, which follows a decline in numbers of cases since a peak in 1998.

According to the NSSLRL, Salmonella Typhimurium and S. Enteritidis were the strains which caused most Salmonella illness in humans in 2011, as in previous years.   Of the 320 Salmonella isolates from patients referred to the NSSLRL in 2011, 27% were identified as S. Typhimurium and 18% as S. Enteritidis. 

Reptiles as a Source of Infection

Reptiles often carry Salmonella and can be a source of infection, especially for children.  The HPSC advises that households with children under five years of age should not keep reptiles as pets; and neither should reptiles be kept in childcare facilities such as crèches.  However, the NSSLRL is concerned that this public health message is not being heeded because reptile-associated cases in children continued to be reported in 2011.  Subtyping of isolates from a number of these cases revealed that the strain which caused illness in the child or children was the same as that carried by the household’s pet reptile.  

NSSLRL annual reports are available at:  www.nuigalway.ie/salmonella_lab/