Severe Salmonella outbreaks predicted in Australia, researchers say

Salmonella outbreaks are likely to become more severe in the future, according to a model developed by University of Sydney researchers.

There are an estimated 93.8 million global Salmonella infections annually, resulting in approximately 155,000 deaths worldwide. Australia is the worst affected country, with the number of Salmonella cases doubling over the last decade. For example, Bridgewater Poultry Farm eggs were recently recalled after Salmonella Enteritidis was detected on the farm.

The model by Sydney researchers can predict Salmonella outbreaks several months in advance, which can help improve the allocation of health resources in future. However, the research team found that outbreaks will become more severe.

Led by Professor Mikhail Prokopenko, Director of the Complex Systems Research Group, they used 2008–2016 strain data to demonstrate that genetic networks of Salmonella pathogens are linked through a few degrees of separation, indicating an increasing severity of future epidemics.

“The data on Salmonella outbreaks in NSW in the last decade or so highlights a continuing ‘arms race’ between pathogens and their human hosts,” explained Prof Prokopenko. “In a classical Darwinian evolution scenario, the pathogens spread over time by initially creating many mutated variants, with the more infectious ‘clones’ soon becoming the most dominant within their own population.”

Salmonella networks operate as ‘small worlds’, the researchers explained, and this close degree of pathogen separation could lead to an aggressive strain and increase the chances of a ‘superbug’.

Complex Systems researcher Dr Oliver Cliff said there has previously been little understanding of how the bacteria has evolved into stronger strains, but the team found correlations between the severity of Salmonella epidemics and the pathogen’s genetic diversity. He said human hosts provide the perfect environment for the bugs to keep evolving.

“We hope this better understanding of Salmonella will lead to enhanced protection of food sources to reduce instances of illness and death,” he said.

To avoid Salmonella infection, people are recommended to stay away from high-risk foods — such as raw or partially cooked eggs, unpasteurised milk and raw ground meat — and wash hands thoroughly after contact with these foods or animals.

The research was published in the journal Scientific Reports.

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