“It’s the worst documented listeriosis outbreak in global history.” So says microbiologist Lucia Anelich, PhD, principal of Anelich Consulting, Pretoria, South Africa, of the devastating public health crisis that has tallied a mindboggling 1,056 cases and 214 deaths as of July 4, 2018.
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According to the South African Department of Health, the source of the outbreak that began in January 2017 has been identified as a bologna-like sausage known as polony. The implicated product containing the outbreak strain was traced to Enterprise Foods in Polokwane.
Enterprise demonstrated the presence of the ST6 strain in its facilities, according to the South African National Institute for Communicable Diseases.
Not surprisingly, massive recalls have been conducted across the country and in neighboring countries that imported those products from South Africa. “An estimated 4,000 tons of food has been recalled,” Dr. Anelich relates. “The recall has included not just polony, but also many other products produced by Enterprise as a precaution.”
Unbelievably, babies are the population group most dramatically impacted by the polony listeriosis tragedy. Some 92 babies have died in South Africa as a result of the outbreak.
“Obviously, babies are not eating polony,” Dr. Anelich relates. “The transmission of Listeria monocytogenes occurs when a pregnant woman eats the contaminated food and transmits the organism via her placenta to the unborn baby. This may result in miscarriage, stillbirth, or preterm delivery. Another potential outcome may be delivery on time, but then the baby could be born with meningitis, pneumonia, or septicaemia from which they may succumb.”
The pregnant mother is often not seriously affected, Dr. Anelich notes. “The mother may only show flu-like symptoms and may never even know that she was infected with the pathogen, if she did not seek medical attention,” she points out.
Dr. Anelich has established a website for consumers that highlights Listeria facts.
The World Health Organization (WHO) is calling the incident in South Africa the largest Listeria outbreak that has ever been detected and is offering assistance in diagnosing and monitoring the organism to any impacted governments as needs arise.
“This Listeria outbreak has been the crisis that made South Africa, and possibly the whole of Africa, realize the importance of food safety and foodborne diseases and the need to invest in improving the control of them,” says Peter Ben Embarek, PhD, WHO’s global food safety specialist. “South Africa has embarked on a deep reform of its food safety system including strengthening of its regulations, standards, and food inspection activities.”
The genus Listeria contains seven species (monocytogenes, ivanovii, seeligeri, innocua, welshimeri, martii, and grayi), two of which are pathogenic. L. monocytogenes is pathogenic to humans and animals; L. ivanovii (previously L. monocytogenes serotype 5) primarily infects animals and very rarely causes disease in humans.
An estimated 1,600 people get listeriosis in the U.S. each year from L. monocytogenes, resulting in some 1,500 hospitalizations and about 260 deaths, according to the CDC.
Along with pregnant women and their newborns, listeriosis is most likely to impact adults aged 65 or older and people with weakened immune systems.
According to Foodsafety.gov, foods particularly susceptible to Listeria contamination include ready-to-eat deli meats and hot dogs; refrigerated pâtés and meat spreads; unpasteurized (raw) milk and dairy products; soft cheese made with unpasteurized milk, such as queso fresco, feta, brie, camembert; refrigerated smoked seafood; and raw sprouts.
“Listeria monocytogenes is found naturally in the environment, such as soil, water, and some animals, including poultry and cattle,” says Dr. Anelich. “So one can therefore realistically expect its presence in low numbers in raw food commodities, including raw poultry and raw meat. This is nothing new. L. monocytogenes has been present in these commodities for decades and many countries that have a long history with listeriosis understand that it is unrealistic to expect raw meats to be completely free of the organism.”
Since raw foods are not sterile, they are not totally free of all microbial life and neither is it a realistic expectation, Dr. Anelich emphasizes.
“It is therefore more important to focus on controlling the organism so that is does not become a risk to human health,” she advises. “This includes, among other things, understanding the behavior of L. monocytogenes in food and in a food processing environment, and developing appropriate risk mitigation strategies.”
Prevention of post-processing contamination of food in a manufacturing facility remains key, Dr. Anelich relates, particularly after a product is cooked, meaning that it received a listericidal treatment (kill step).
“L. monocytogenes is known to become persistent in the environment of some facilities and could therefore be a consistent source of post-processing contamination,” Dr. Anelich points out. “A robust environmental monitoring and control program is vital, which would include, amongst other important considerations, hygienic design of equipment and facilities, and an ongoing effective cleaning and disinfection regime.”