Foodborne Disease Outbreak Investigations Research Articles

Characteristics of Foodborne Disease Outbreak Investigations Conducted by Foodborne Diseases Active Surveillance Network (FoodNet) Sites, 2003–2008

A mean of ≥ 1000 foodborne disease outbreaks (FBDOs) causing ≥ 20,000 illnesses are reported to the Centers for Disease Control and Prevention (CDC) annually. We evaluated characteristics of successful outbreak investigations (ie, those that identified an etiologic agent or food vehicle) in the Foodborne Diseases Active Surveillance Network (FoodNet). FBDOs were defined as the occurrence of ≥ 2 cases of a similar illness resulting from ingestion of a common food. FBDOs reported to CDC Foodborne Disease Outbreak Surveillance System during 2003-2008 with FoodNet supplemental data available were included in the analyses. Data regarding 1200 FBDOs were available. An etiologic agent was confirmed in 715 (60%); a food vehicle was identified in 387 (32%). At least 4 fecal specimens were collected in 425 of 639 outbreaks (67%) with a confirmed etiologic agent and 48 of 232 (21%) without a confirmed etiologic agent (odds ratio [OR], 7.6; 95% confidence interval [CI], 5.3-10.9). A food vehicle was identified in 314 (47%) of 671 outbreaks investigated using a case-control or cohort study, compared with only 73 (14%) of 529 outbreaks investigated by using other methods (OR, 5.5; 95% CI, 4.1-7.3). At least 1 barrier affecting the success of the investigation was reported for 655 outbreaks, including too few patients (n = 172; 26%), too few stool specimens (n = 167; 25%), and too few control subjects (n = 152; 23%). Etiologic agent and vehicle are frequently undetermined in FBDOs. Greater emphasis on fecal specimen collection and overcoming barriers to pursuing analytic epidemiologic studies can improve ascertainment of these factors.

Detection and Differentiation of Coccidian Oocysts by Real-Time PCR and Melting Curve Analysis

Rapid and reliable detection and identification of coccidian oocysts are essential for animal health and foodborne disease outbreak investigations. Traditional microscopy and morphological techniques can identify large and unique oocysts, but they are often subjective and require parasitological expertise. The objective of this study was to develop a real-time quantitative PCR (qPCR) assay using melting curve analysis (MCA) to detect, differentiate, and identify DNA from coccidian species of animal health, zoonotic, and food safety concern. A universal coccidia primer cocktail was designed and employed to amplify DNA from Cryptosporidium parvum, Toxoplasma gondii, Cyclospora cayetanensis, and several species of Eimeria, Sarcocystis, and Isospora using qPCR with SYBR Green detection. MCA was performed following amplification, and melting temperatures (T(m)) were determined for each species based on multiple replicates. A standard curve was constructed from DNA of serial dilutions of T. gondii oocysts to estimate assay sensitivity. The qPCR assay consistently detected DNA from as few as 10 T. gondii oocysts. T(m) data analysis showed that C. cayetanensis, C. parvum, Cryptosporidium muris, T. gondii, Eimeria bovis, Eimeria acervulina, Isospora suis, and Sarcocystis cruzi could each be identified by unique melting curves and could be differentiated based on T(m). DNA of coccidian oocysts in fecal, food, or clinical diagnostic samples could be sensitively detected, reliably differentiated, and identified using qPCR with MCA. This assay may also be used to detect other life-cycle stages of coccidia in tissues, fluids, and other matrices. MCA studies on multiple isolates of each species will further validate the assay and support its application as a routine parasitology screening tool.

Trends in food-borne disease.

Abstract Food-borne disease is widespread around the world, with its most serious consequences affecting those who are young, old and already ill. Chemical contaminants are present in much of the food supply but usually at levels not associated with adverse human effects. However, there are occasional problems from natural toxins that can cause local disease and restrict international trade. Much of food monitoring is focused on testing foods to meet the national standards for mycotoxins and pesticide residues. More recently, there have been concerns over specific chemicals such as acrylamide, food dyes and melamine as well as allergens, but there is no routine testing for these chemicals. Despite this concern over chemicals and their monitoring, most of the known illness relates to microbial contamination, and surveillance systems focus on that which links to human illness. Interestingly, many foods that have been associated with outbreaks would not have been thought of as vehicles from the then-existing microbiological studies, e.g. Salmonella in chocolate and peanut butter; Escherichia coli O157:H7 in apple cider and sprouts and Listeria monocytogenes in hot dogs. Many steps have to be taken to bring a food-borne disease outbreak investigation to a successful conclusion. As is so often the case, if key data are missing or the different players in the investigation do not coordinate effectively, not only will many ill persons not be identified, but also the cause of the outbreak may not be determined. Surveillance can comprise two main systems: complaint or notification systems, and pathogen-specific surveillance. The former may trigger an investigation and the latter leads to interpretation of case trends over periods of time. More recently there has been interest in syndromic surveillance as a way of rapidly detecting an event even if the causative agent may not yet been identified. Most countries have some kind of disease surveillance system and these usually include enteric diseases but not necessarily food-borne disease per se . Among those countries that do, they tend to have their own approach to surveillance, which is mainly passive in letting the local investigators prepare the reports and communicate these to national levels. An important step in food-borne disease surveillance is the development and maintenance of an active system, such as FoodNet and PulseNet in the USA, even if it is time-consuming and expensive. This is because they can be very useful in predicting the burden of food-borne disease at the national level and what the main risk factors are that lead to infections, which in turn help direct control measures. A new concern today is the threat of deliberate contamination of food, and early disease detection systems that link to first responders are being developed. In preparation for such an event, not only do public health personnel need to be involved, but also law enforcement officers who have a different mandate. This threat is stimulating better traceability methods particularly for imported foods, and having governments and industry being more concerned over fraud, counterfeiting and smuggling. Eventually, food-borne disease surveillance systems will become integrated internationally, as they are starting to do within Europe and under the direction of the World Health Organization.

Application of foodborne disease outbreak data in the development and maintenance of HACCP systems

Five-hundred and thirty general foodborne outbreaks of food poisoning reported in England and Wales between 1992 and 1996 were reviewed to study their application to the development and maintenance of HACCP systems. Retrospective investigations of foodborne disease outbreaks provided information on aetiological agents, food vehicles and factors that contributed to the outbreaks. Salmonella spp. and foods of animal origin (red meat, poultry and seafood) were most frequently associated with outbreaks during this period. Improper cooking, inadequate storage, cross-contamination and use of raw ingredients in the preparation of food were the most common factors contributing to outbreaks. Classification and cross tabulation of surveillance information relating to aetiological agents, food vehicles and contributory factors facilitates hazard analysis. In forming control measures and their corresponding critical limits, this approach focuses monitoring on those aspects that are critical to the safety of the product. Incorporation of epidemiological data in the documentation of HACCP systems provides assurance that the system is based on the best scientific information available.

Grade A Eggs as a Source of Salmonella enteritidis Infections-Reply

In Reply.— Mr Thomas evidently misunderstood the epidemiologic methods that were the core of our report. We did not interview persons 1 or 2 years after their illness. Rather, state and local health departments routinely investigate food-borne disease outbreaks at the time of occurrence, recording specific epidemiologic data such as food-specific attack rates and microbiological tests of foods. The epidemiologic findings we reported from 1985 through 1987 therefore represented an analysis of the aggregate results from an extensive series of independent investigations of food-borne disease outbreaks reported to the Centers for Disease Control. Our ability to collect and analyze 65 S enteritidis outbreaks occurring in the northeastern United States testifies to the extraordinary rise of this one serotype of Salmonella as an agent of food-borne disease in recent years. Grade A eggs or foods containing such eggs were implicated in 77% of these S enteritidis outbreaks in which the vehicle