Salmonella: Duck Eggs, Frogs & Others

Ducks in my home village, China /© 2008 Am Ang Zhang

Years back when I was a medical student, we were taught that ducks basically carry salmonella as a matter of course due to their aquatic habitat and for that reason the Chinese have always been careful to make sure that ducks are well cooked unlike some modern day fancy cooking where duck meat is often presented rare. 

As it is coming up to Chinese Moon Festival time, it is worth mentioning that our moon cake often have one or two duck egg yolks in them, yes, salted egg yolk in moon cake. They too are of course well cooked.

Recently there has been an outbreak of Salmonella Typhimurium DT8 food poisoning in the UK.

The Health Protection Agency (HPA) reported:

HPA investigates a national outbreak of salmonella

17 September 2010

The Health Protection Agency (HPA) has investigated an on-going national outbreak of Salmonella Typhimurium DT8. 

Salmonella Typhimurium DT8 causes a similar illness to other forms of Salmonella infection, so symptoms can include diarrhoea, vomiting, abdominal pain and fever.

So far this year, the HPA has confirmed 66 reports of human infection in England and Northern Ireland.  Figures for previous years were 34 in 2008 and 47 in 2009.   

Of the reported cases two are known to have been hospitalised, one of whom has died. Cases are mainly adults with an average age of 46 years, and most are men (61 per cent).  Cases have been referred from Northern Ireland and most regions in England, with predominance in the South East and North West.   

 “It became clear from our investigations that the increase was related to the consumption of duck products, mainly eggs. It is important that consumers and caterers are aware that all eggs, including duck eggs, may occasionally be contaminated with Salmonella and follow advice provided by the Food Standards Agency in order to reduce the risk of infection. Eggs should be cooked thoroughly and good hygiene practices, such as washing hands, utensils and kitchen surfaces should be followed after handling or using duck eggs.”

There is of course another very important source of the infection: pets especially frogs and turtles.

Center for Disease Control (CDC) reported earlier in the year:

Multistate Outbreak of Human Salmonella Typhimurium Infections Associated with Aquatic Frogs --- United States, 2009

Strawberry poison dart frog (nicknamed Blue Jean frog)
- Dendrobates pumilio/© 2008 Am Ang Zhang

During April--July 2009, the Utah Department of Health identified five cases of Salmonella Typhimurium infection with indistinguishable pulsed-field gel electrophoresis (PFGE) patterns, predominantly among children. In August, CDC began a multistate outbreak investigation to determine the source of the infections. This report summarizes the results of this ongoing investigation, which, as of December 30, had identified 85 S. Typhimurium human isolates with the outbreak strain from 31 States.

31 States!!!

Environmental samples taken from patient homes in four states yielded the outbreak strain of S. Typhimurium. The Colorado Department of Public Health obtained matched isolates from two African dwarf frogs, and from a rock and water in the aquarium containing the two frogs. The New Mexico Department of Health matched the outbreak strain with isolates from the filtration system, gravel, and water from an aquarium in a patient's home containing fish and a small water frog. The Ohio Department of Health matched the outbreak strain with isolates from a patient's deceased African dwarf frog, its water, and the lid and edge of its aquarium. The Utah Department of Health obtained matched isolates from a container used to clean African dwarf frogs in a patient's home.

Traceback investigations of frogs associated with positive environmental isolates have been completed. African dwarf frogs from the homes of the Colorado patient and the Utah patient were prizes from games at two different carnivals. The vendor who distributed the frogs to both carnivals was from Utah and identified the source as a breeder in California. Environmental sampling from the vendor's home (of aquarium filters and skin previously shed from African dwarf frogs) yielded multiple isolates matching the outbreak strain. The aquatic frog from the home of the New Mexico patient was purchased from a pet store chain, whose distributor identified the same breeder as the source for all of its aquatic frogs. The family of the Ohio patient purchased its African dwarf frog from a department store, whose distributor identified the breeder as the ultimate source of its frogs.

Environmental sampling from the breeder's California facility yielded S. Typhimurium isolates matching the outbreak strain. Positive samples were collected from multiple locations in the facility, including water tanks that contained African dwarf frogs and gravel in the water filtration system.

CDC’s advice:

• Persons at increased risk for serious infection from salmonellosis are children < 5 years old, elderly persons, and persons with weakened immune systems.
• These persons should avoid contact with amphibians (e.g., frogs) and reptiles (e.g., turtles) and anything that comes in contact with them (e.g., aquarium, habitat, and water).
• Keep amphibians and reptiles out of homes with children < 5 years old or people with weakened immune systems.

Read more at CDC>>>>>>

CDC: Poultry, Reptiles & Amphibians

Iguana iguana, Costa Rica/© 2007 Am Ang Zhang

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