Listeria in Raw Milk Soft Cheese: A Case Study of Risk Governance in the United States Using the IRGC Framework

Abstract

Between 1980 and 1996 there were 30 known and reported outbreaks of foodborne illness associated with cheese consumption in the United States, Canada, Europe, and Scandinavia (Cody et al. 1999), and 16 of these outbreaks were associated with cheese produced using unpasteurised milk contaminated with one or more of the following pathogens—Brucella sp., Escherichia coli, Listeria monocytogenes, Salmonella spp., and Yersinia enterocolitica (Teuber 2000). In this chapter, we will focus on only one of these pathogens—Listeria monocytogenes (Lm). Of the above outbreaks, three were caused by Lm, which resulted in 284 reported illnesses and 86 deaths (Teuber 2000). Periodic outbreaks of listeriosis from cheese have continued to occur; at least another six Lm outbreaks in the US, four in Europe, and two in Canada have been associated with cheese consumption since 1996 (de Valk et al. 2005; Food Safety Network 2005; Pagotto et al. 2006; US Food and Drug Administration Center for Food Safety and Applied Nutrition [FDA CFSAN] et al. 2003). Listeria is a genus of bacteria that includes six separate species that can be found throughout the natural environment, for example, in the feces of mammals, on vegetation, and in silage. The Lm strain was first identified in 1926 following an outbreak in rabbits (CFSAN 1992), but has only gained significant interest by the US federal regulatory bodies in the past 20 years (Woteki and Kineman 2003). Lm is commonly found in the gastro-intestinal tract of several animal species and humans. It has been found in at least 37 mammal species, 17 species of birds, and both fish and shellfish; and is believed to be present in up to 10% of humans (CFSAN 1992). Lm is the primary causative agent of listeriosis. Listeriosis can be distinguished as two types: invasive and non-invasive. Invasive listeriosis is the severe form of the disease which typically has a two to three week incubation time, but can extend up to three months. Adverse outcomes can include septicemia, meningitis, encephalitis, abortion or stillbirth, endocarditis, cutaneous infections, and, though rare, it may cause focal infections, such as endophthalmitis, septic arthritis, osteomyelitis, pleural infection, and peritonitis (FDA CFSAN et al. 2003). Non-invasive listeriosis causes gastrointestinal illness, which may result in chills, diarrhea, headache, abdominal pain and cramps, nausea, vomiting, fatigue, and myalgia. The frequency of contracting non-invasive Lm is unknown because most of the cases are not reported to public health officials (FDA CFSAN et al. 2003).