Know thy enemy – listeriosis

As the Department of Health (DoH) attempts to hunt down the source of the listeriosis disease causing bacteria Listeria monocytogenes, it is evident more information on this deadly bug is needed.

With 61 people dead, 40% of who were neonatal babies, The Citizen reached out to international food safety expert Dr Lucia Anelich, the only South African member of the International Commission on the Microbiological Specifications for Food, current president of the South African Association for Food Science and Technology, and chair of the SABS Food Hygiene Committee.

“Listeria was not a known problem for humans prior to the early 1980s, and was more commonly known to cause disease in animals, However, bacteria and viruses change or simply switch host and this can be due to environmental pressure, any number of things,” said Anelich, stating this was the worst documented listeriosis outbreak in global history.

“The organism is an environmental pathogen and is found in soil, water, sewage, and decaying vegetation. Because bacteria and viruses are biological entities, they can mutate or pick up genes from other microorganisms in their environment, they are constantly together.”

This could lead to either the creation of a completely new microorganism or a different strain.

Known to have been around in one form or another for decades, the last massive listeriosis outbreak in 2011 in the US finally traced to cantaloupes which killed 30 people and infected 147 others.

Last year, the DoH said Listeria monocytogenes was detected in 60 to 80 cases annually.

“The organism can be readily isolated from humans, domestic animals, raw agricultural commodities, and food packing and processing environments, particularly cool damp areas that can contaminate food,” Anelich noted.

According to Anelich, Listeria monocytogenes could cause two types of illness, a mild, non-invasive illness – called listerial gastroenteritis – which showed typical symptoms of a tummy bug i.e. fever and diarrhoea.

“This form of the illness is rarely diagnosed and usually passes quickly without severe effects,” said Anelich.

The other side of the coin was the severe, invasive illness responsible for infecting up to 727 people so far.

“Listeriosis is characterised by a relatively high mortality rate of between 20 to25% compared to most other foodborne pathogens such as Salmonella (less than 1%) or E. coli O157. In the invasive form of the illness, the organism has moved beyond the gut and has infected other parts of the body,” Anelich said.

Foods most often implicated in foodborne outbreaks globally ready-to-eat deli meats (polonies, ham products, hot dogs, refrigerated pâtés or meat spreads, unpasteurised milk and dairy products, soft cheese made with unpasteurised milk, such as queso fresco, Feta, Brie, Camembert, also refrigerated smoked seafood, raw sprouts, pre-packaged salads, and ice cream, although not as common said Anelich.

“Pregnant women are approximately 20 times more likely than other healthy adults to get listeriosis. They typically experience only fever and other flu-like symptoms, such as fatigue and muscle aches. However, infections during pregnancy can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the new-born, such as meningitis,” Anelich noted.

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