Manufacturers and regulators must learn from listeriosis mistakes

In 1981 a significant listeriosis outbreak in Nova Scotia, Canada, resulted in 41 cases and 18 deaths. In this incident, the contamination was traced to coleslaw. Cabbages grown on a farm where listeria-contaminated sheep manure was used as a fertiliser were found to be the source of the outbreak. At the time, it was the largest outbreak of its kind in the world and the first time that listeria monocytogenes was proven to cause food-borne illness in humans. In 2002, a listeriosis outbreak in Quebec involved 17 cases and was also associated with cheese.

However, in the summer of 2008 Canada had its most lethal contact - with two separate outbreaks of the pathogen. The initial outbreak, again linked to cheese, gave rise to 38 confirmed cases and two deaths in Quebec. However, this was not related to the second and most devastating outbreak. By the end of this outbreak, listeriosis was confirmed in 57 people and was reported as the underlying or contributing cause of death for 22 of these individuals. Though the majority were in Ontario, illnesses occurred in seven provinces throughout the country.

The 181-page Report of the independent investigator into the 2008 listeriosis outbreak begins by emphasising that the numbers mentioned above do not adequately describe the human impact of this outbreak, which affected mostly frail, elderly individuals living in long-term care homes. Several people hospitalised because of other diseases, such as cancer that weakened their immune systems that left them susceptible to listeria infection, also fell ill.

In fact the outbreak analysis shows that almost 80 per cent of those who developed listeriosis lived in a long-term care home or was admitted to a hospital that had served deli-meats taken from large packages contaminated with listeria monocytogenes.

Back to the source

The outbreak was eventually traced to Maple Leaf Foods of Weston, Ontario. The report notes that like all firms operating food processing plants regulated by the federal government, Maple Leaf Foods was required to maintain a hygienic operating environment in order to control bacteria.

According to the report, at the outset of the 2008 listeriosis outbreak, Maple Leaf Foods was viewed as a good company using the latest food safety control systems. It viewed itself then, and continues to view itself now, as a leader in the industry.

The Bartor Road plant was considered by many to be a compliant plant in that it routinely met all the regulatory requirements under the federal Meat Inspection Act and got satisfactory marks for complying with the government's inspection and testing tasks.

When Canadian Food Inspection Agency's (CFIA) inspectors identified any compliance problems, the plant addressed them. Bartor Road's management maintained the necessary required records, ensured that staff training took place, and made sure its quality assurance programme was completed.

Much of the credit for Maple Leaf Foods' good reputation rested with the firm's in-house safety plan. The company had introduced its own food safety procedures - which includes a comprehensive HACCP1 plan, an additional layer of food safety protection at the end of the 1990s - years earlier than was required by the regulations.

Like most food processors, Maple Leaf Foods' food safety approach laid out a hazard monitoring and control programme. As a general rule, these plans are effective. Over 400 meat processing companies across the country produce tonnes of food products daily without incident. In fact, like many of Canada's ready-to-eat meat processing plants, Bartor Road actually went beyond the policy and requirements in that the company had an extensive environmental testing programme of its own. Doing more than was required did not guarantee the company was trouble-free.

As early as summer and fall of 2007, the company's environmental testing programme showed positive listeria environmental test results from production lines 7 and 8 in the plant, every two to three weeks, at various locations on those lines.

This pattern carried on into 2008 (see Table 1). For example, in the first week of February, the plant's environmental test results showed an increase in the number of positive listeria results from line 7. The problem also occurred in March and April when increased numbers of positive listeria test results showed up on line 8, every two to three weeks. During the week of 19 May, more positive test results appeared on the plant's lines 7 and 8. With the benefit of hindsight, we now know that this problem persisted over several months before 3 June onset of the first case of human illness linked to contaminated Maple Leaf Foods deli meat products. Positive results for listeria from environmental testing were also identified during the week of 23 June.

In each instance, the plant staff took action to destroy the bug. They employed a 'search and destroy' approach - the recognised standard procedure - sanitising all the surfaces where the bacteria could grow on production lines and throughout the building. Every time employees intervened, the follow-up test results were negative, at least for awhile. This led to the assumption that the problem had been solved, creating a false sense of security.

What was missing was the big picture - recognising the repeated pattern of presence of listeria on the same production lines several weeks after the problem was presumed to have been fixed.

The report then goes into considerable detail about how food safety is managed in Canada and looks more closely at how the events of 2008 were managed: everything from equipment suppliers to the information supplied to the public by the government comes under its spotlight.

It concludes with 57 recommendations, including:

- To enhance food safety awareness of meat processors including but not limited to Federally-registered ones: the ceo and senior management of all meat processors should accept oversight responsibility for ensuring that food safety is fully embedded in every level of their business; the ceo and senior management of all meat processors should ensure effective design and actively promote all aspects of food safety consistent with their Food Safety Plan; such plans should be regularly updated to ensure on-going attention to pathogen control; all meat processors should ensure that new and existing equipment is and remains appropriate for the intended use; sanitation methods should be validated and implemented by meat processors in consultation with the equipment manufacturer, with a particular focus on the intended use and the products being processed on each piece of equipment.

- To improve sanitation of food processing equipment, manufacturers of food processing equipment should ensure that their specifications and instructions to users specifically emphasise the necessity to control the risk of pathogens, including listeria monocytogenes. In addition, manufacturers of food processing equipment should accept responsibility for the foreseeable impact of the design and operation of their equipment on food safety. The design and operation of, and recommended sanitation methods for all food processing equipment should: enable thorough cleaning and disinfection; allow for efficient and complete disassembly and reassembly when required; eliminate to the fullest extent possible all areas likely to harbour pathogens, including listeria monocytogenes; wherever possible, use material that is scientifically validated to limit pathogen growth or survival; and be peer-reviewed (applicable only for the recommended sanitation methods).

- Finally, the report concludes that to demonstrate its commitment to food safety, the government of Canada should be mindful that due to globalisation and increased Canada-wide production and distribution of food, food safety will require increased attention.

TABLE 1.

Key dates of the outbreak (source: July 2009 Report of the Independent Investigator into the 2008 Listeriosis outbreak).

- February to July (2008) - sporadic positive listeria test results at Bartor Road plant.

- 3 June - earliest known human illness linked to the listeriosis outbreak.

- 17 June - first death linked to listeriosis from contaminated Maple Leaf Foods product.

- 10 July - first two listeriosis cases in the outbreak identified through DNA fingerprinting.

- 18 July - Maple Leaf Foods first identified as possible source of contaminated food products.

- 22 July - 11 food samples from Toronto long-term care home sent for testing.

- 29 July - more than double the normal number of listeriosis cases (24 v 11 expected) reported by almost half of Ontario public health units.

- 4 August - food samples from long-term care home test positive for listeria monocytogenes.

- 7 August - The Canadian Food Inspection Agency (CFIA) initiates a food safety investigation.

- 12 August - DNA fingerprinting matches cases from several provinces.

- 13 August - Maple Leaf Foods advises distributors to hold certain products.

- 16 August - THE CFIA confirms listeria monocytogenes in Maple Leaf Foods products

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