Listeriosis – A Killer on the Loose

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Listeriosis is a disease caused by the bacterium called Listeria monocytogenes (L. monocytogenes).  The Listeriosis outbreak in South Africa killed at least 180 people and infected almost 1000 others since January 2017.  It was the world’s worst recorded listeria outbreak.

The National Institute for Communicable Diseases eventually identified the culprits on 4 March 2018.  L. monocytogenes were found in ready-to-eat processed meats (polony and sausages), manufactured by two meat processing companies.

On 3 September 2018, the Health Minister, Aaron Mostoaledi officially announced the end of the outbreak.  The South African economy lost hundreds of millions, and the meat processing industry took a big knock.

The outbreak might be over, but there could be severe ramifications for the companies concerned.  A double edge sword hangs over their heads.  Victims and family members of victims might launch a class action suit and/or possible Government fines imposed as per the South African Consumer Protection Act, No 68 of 2008.

Where Do You Find Listeria Monocytogenes Bacteria?

You find it in the environment, including soil, water, and many other environmental sources.  It also survives in the digestive systems of at least 37 species of mammals (both domestic and wild), birds (17 species identified), and some fish and shellfish species.  Did you know, up to 10% of humans might be intestinal carriers of the bacteria?


L. monocytogenes is common in the environment and livestock. This is the main reason why it is frequently found in vegetables and uncooked meat. L. monocytogenes is resistant to adverse conditions and can survive freezing, drying, high salinity and low heat.

Food Sources That Might Contain Listeria Monocytogenes Bacteria

These are only a few examples, and you should take precautions when consuming raw, undercooked and under heated food products.  Rinse vegetables and fruit properly and remember to wash your hands before and after working with food.

Meat and Cheese Platter
Cold Meat and Certain Cheeses
  • Unpasteurized (raw) milk and dairy products
  • Ready-to-eat deli meats and hot dogs
  • Soft cheese made with unpasteurized milk, such as Feta, Brie, queso fresco, Camembert
  • Refrigerated meat spreads and pâtés
  • Refrigerated smoked seafood
  • Raw sprouts

In recent years soft-ripened cheeses and under pasteurized milk have caused several cases of infection, but during the recent listeriosis outbreak in South Africa, ready-to-eat (RTE) meat (cold meats) and poultry products were the main culprits.

Who is at Risk?

L. monocytogenes is especially pathogenic to high-risk human populations such as:

  • newborns
  • pregnant women
  • the elderly
  • people with weakened immune systems, such as persons immunocompromised by anticancer drugs, graft-suppression therapy and AIDS
Pregnant Women and the Elderly
Pregnant Women and the Elderly

Other conditions that may increase susceptibility to Listeriosis are:

  • diabetes
  • cirrhosis
  • asthma
  • ulcerative colitis
  • end-stage renal disease
  • liver disease
  • alcoholism

Healthy people are generally at low risk of contracting L. monocytogenes-related illnesses, but heavily contaminated food can make any person susceptible to infection.

Although listeriosis infections are relatively uncommon, it is a potentially fatal disease.  Frequent spontaneous abortions do occur in pregnant women who are infected with the bacteria.

Even though the symptoms may be relatively mild in the mother, the infection may be transferred to the foetus, causing severe illness or foetal death.

The Symptoms of Listeriosis

Symptoms of L. monocytogenes may include:

  • fever
  • stiff neck
  • confusion
  • weakness
  • vomiting sometimes preceded by diarrhoea
  • meningitis
  • encephalitis
  • septicaemia
  • spontaneous abortion
  • stillbirth
  • influenza-like symptoms

The disease’s onset can occur anywhere from a few days up to 6 weeks after the ingestion of L. monocytogenes bacteria.  The symptoms last from a few days to several weeks.

Listeriosis is clinically defined when the bacterium is isolated from blood, cerebrospinal fluid, or otherwise sterile site (such as the placenta).

The Responsibilities of Food Handling Organisations

The South African Listeriosis outbreak has resulted in an unprecedented public health risk.  The industry could have easily avoided this.  Food handling organisations have to ensure that steps are taken at all production levels to prevent contamination of meat products by Listeria monocytogenes.

While this is a difficult task, given that L. monocytogenes is so widespread in the environment, the recent outbreak has shown that it is a necessary precaution.

Food-processing operations need to make every effort to prevent L. monocytogenes in raw, unprocessed foods and recontamination in precooked, RTE finished products.

Due to foodborne illness associated with L. monocytogenes in meat and poultry products, the USDA has issued a zero-tolerance policy for the organism in RTE foods.

How Do You Effectively Control Listeria Monocytogenes in Your Organisation?

Effective control of L. monocytogenes is challenging.  It requires intensive management and extensive resources.

This is usually in the form of effective HACCP and Food Safety Management Systems that ensure that food production facilities ascribe to the highest food safety standards.

Even though the risk of contracting listeriosis is relatively low, the consequences are devastating for both the consumer and the processor when it does occur.

The presence of L. monocytogenes in raw ingredients emphasises the importance of adequate cooking (thermal processing) to destroy the organism.

Preventing the spread of Listeriosis starts with proper housekeeping and cleaning. Factory employees need to ensure they maintain good hygiene practices all the time. Factories need to be thoroughly cleaned and disinfected. Proper verification systems, including taking micro swabs, visual observation, etc., become necessary to ensure the effectiveness and efficiency of cleaning.

Well Trained Staff Can Help Prevention

Employee training also plays a vital role in controlling contamination problems.  Employees must understand the organism, observe basic sanitation principles, and gain the same sense of personal responsibility exhibited by management and regulatory officials.

ASC Consultants has a wide range of training modules available to help employees understand Listeriosis and its preventative measures.

You are welcome to Contact Us for more information.


Listeria monocytogenes bacteria are common in the environment, and we will never be able to avoid it, but we can prevent Listeriosis.  Good personal hygiene practices and taking the necessary food safety measurements in the workplace will make a difference.

Awareness is key!

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2 thoughts on “Listeriosis – A Killer on the Loose”

  1. Listeria outbreaks are very scary. There have been many Listeria outbreaks reported worldwide every year. Most of these outbreaks are mainly due to the lack of proper food handling practices. This is a very informative article about Listeriosis. It is important to know what Listeria is and whom is most susceptible to contracting this potentially deadly disease. I am very careful when handling and preparing food and do not take any chances. If I have any doubts about any food products I don’t buy it or it gets tossed.

    • Hi Monika,
      Thank you very much for having a look at our post. Good food handling practices are not only the manufacturer’s responsibility, but the consumer should also be vigilant when preparing and cooking food.


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