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25 July 2002
Research projects commissioned by MAF and Ministry of Health into a
disseminated outbreak of a 'new to New Zealand' strain of Salmonella between
1998 and 2002 have been completed.
The research was conducted by scientists from the Institute of Environmental
Science and Research (ESR) and Massey University and covered both human and
animal impacts of the outbreaks.
Matthew Stone, Exotic Disease Co-ordinator for the Ministry of Agriculture
and Forestry (MAF) said the research provided a valuable insight into the risks
associated with introduction of foreign salmonellae and why strong links between
animal and human health scientists are required to investigate instances of
disease transmission across species.
"This outbreak has provided an opportunity for MAF, Ministry of Health,
Department of Conservation and research scientists from ESR and Massey
University to be involved in an outbreak response and subsequent studies for a
disease with clear human health and environmental implications."
Dr Stone said an important outcome from the study was the need to develop an
integrated interagency approach to salmonellae surveillance in New Zealand.
"The research showed that there are limitations in the New Zealand
surveillance of animal Salmonella infection. The systems in place for data
collection on positive samples and isolates referred to the national salmonellae
reference laboratory at ESR for definitive typing need to be strengthened.
Although tests confirmed that the particular strain of Salmonella Typhimurium
DT160 was new to New Zealand they were unable to show how the disease entered
the country or its origin.
Dr Stone said possible means of introduction included migratory birds or
imported contaminated animal feed, or human travellers.
"There is a reservoir of infection of DT160 in sparrows and probably
other birds now. Infections in other animals and humans will continue as a
result of infection acquired from this source," he said.
Because the strain is now widely dispersed in the environment, people should
be reminded that safe food handling practices are essential, both in the home
and in food businesses, to prevent food borne illnesses.
Douglas Lush from the Ministry of Health recommended that people avoid, where
possible, contact with wild birds, including dead birds, or food and water
contaminated with infected bird droppings. If contact is unavoidable they should
wash their hands afterwards.
The symptoms of salmonella infection are stomach cramps, fever, vomiting and
diarrhoea. Anybody with these symptoms should see a doctor.
Salmonella Typhimurium DT160 was first isolated from a child in Christchurch
in 1998. Since then, it has rapidly become an important human infection. In 2001
the strain was the cause of 34% of the total cases of salmonellosis in New
In 2000 the strain was determined as a cause of spring die-off in sparrows in
Christchurch, and in subsequent years was associated with die-off in other
regions. The strain has now been isolated from a wide range of other animals and
MAF remains interested in investigating the cause of unusual bird deaths.
Reports of unexplained bird mortality events involving more than 20 birds should
be reported to the MAF Exotic Disease Hotline 0800-809-966.
For more information contact: Matthew Stone MAF Biosecurity 04 498-9884
Philippa White MAF Biosecurity 04 498 9948 or 025 223 1875
Zoe Priestly Ministry of Health: 04 496 2483 025 277 5411
Fiona Thomson-Carter ESR: 04 9140753