Changes in climate fuel listeriosis

Enterptise polony
Enterptise polony
Image: ALAISTER RUSSELL

South Africa's changing climate could fuel listeriosis outbreaks.

Several features of the microbe that cause the life-threatening disease make it, especially climate sensitive, scientists warn in the June edition of the South African Medical Journal.

"Spikes in ambient temperature and high summer temperature peaks, for example, have been linked to the occurrence of listeriosis, as with most diarrhoeal pathogens," they said.

"Hot weather extremes that become more common with climate change augment the replication cycles of listeria monocytogenes and could cause breakdowns in food-cooling chains, with rapid rises in numbers of the bacteria on food products."

Altered rainfall patterns and longer dry seasons - such as those experienced in western regions of South Africa - may influence listeria transmission, said Matthew Chersich from Wits University, and fellow authors Fiona Scorgie, Helen Rees and Caradee Wright.

The world's worst listeriosis outbreak - with more than 1000 confirmed infections and 200 deaths - began early last year, and the source of the outbreak was traced to Tiger Brands' Enterprise Polokwane plant.

The plant was closed, but Chersich said it was important that longer-term, structural factors were also dealt with.

"Ultimately, infectious disease outbreaks, which may become more frequent with rising ambient temperatures and water scarcity, are the proverbial canary in a coal mine," he says.

Water scarcity may hamper efforts to clean machines used for slicing and chopping.

Changes in the sources of water could also influence the spread of listeria, Chersich added. "In both rural and urban areas, roof-harvested rainwater is increasingly being used for irrigation and domestic purposes. A study of rainwater tanks in villages in three provinces found that 22% of samples were contaminated with listeria monocytogenes, possibly from bird faeces and debris on rooftops."

Finally, changes in rainfall patterns caused by climate disruption can also affect listeria dispersal. They called for closer monitoring of food industry standards.

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