Producing Safe Eggs

Microbial Ecology of Salmonella

Steven Ricke, Richard K Gast

• Publisher: Academic Press
• Year: 2016
• Print ISBN: 9780128025826
• eBook ISBN: 9780128026779
• Topic: Technology & Engineering
• Subtopic: Microbiology
• Index: Technology & Engineering

Producing Safe Eggs: Microbial Ecology of Salmonella takes the unique approach of interfacing problems of Salmonella and microbial contamination with commercial egg production. It presents in-depth information on microbial contamination, safety and control, physiology, immunology, neurophysiology, and animal welfare, which makes this book a complete reference for anyone involved in the safe production of eggs and egg products in the food industry.This book discusses management and risk factors across the entire egg production process, including practical applications to decrease disease and contaminated food products in poultry houses, processing plants and retail businesses. It is an integral reference for food scientists, food safety and quality professionals, food processors, food production managers, and food business owners, as well as students in food science, safety, microbiology, and animal science.- Includes pre- and post-harvest control measures to reduce microbial contamination and salmonella risks- Presents hot topics regarding vaccination, egg-in-shell pasteurization, and other new technologies currently under development- Provides risk assessment strategies for implementation in business operations- Discusses management and risk factors across the entire egg production process, including practical applications to decrease disease and contaminated food products in poultry houses, processing plants, and retail businesses- Offers a complete reference for anyone involved in the safe production of eggs and egg products in the food industry

Section 1

Salmonella in Egg Production Systems: International Prevalence, Issues, and Challenges

Outline

Chapter 1. Of Mice and Hens—Tackling Salmonella in Table Egg Production in the United Kingdom and Europe

Chapter 2. Microbiology of Shell Egg Production in the United States

Chapter 3. Egg Production Systems and Salmonella in Korea

Chapter 4. Egg Production Systems and Salmonella in Canada

Chapter 5. Egg Production Systems and Salmonella in Australia

Chapter 6. Egg Production Systems and Salmonella in South America

Chapter 1

Of Mice and Hens—Tackling Salmonella in Table Egg Production in the United Kingdom and Europe

Francesca Martelli, Andrew Wales, and Rob Davies Animal and Plant Health Agency (APHA), Addlestone, United Kingdom

Abstract

Laying hens can become infected with a number of non–host-specific Salmonella serovars, of which Salmonella Enteritidis and Salmonella Typhimurium (including monophasic strains) are considered the most relevant threat to public health in Europe. S. Enteritidis in particular is able to persist indefinitely on layer farms unless effective interventions are implemented. In 2014, 2.5% of adult laying flocks in the European Union were reported to be infected by Salmonella (0.9% with either S. Enteritidis or S. Typhimurium). Laying hens can become infected as a result of contact with a contaminated environment (either at the hatchery or farm). Once Salmonella infection is established in a flock, it is perpetuated through a fecal–oral cycle. Rodents, particularly house mice, play a major role in the persistence of the infection, especially for flocks infected with S. Enteritidis. Rodents can readily become infected via contact with feces and dust and harbor salmonellae in their intestines and liver, where they can multiply to high numbers and persist for the whole life of a wild mouse. Contamination of feeding and water supply systems and surfaces of buildings and equipment by rodent droppings leads to infection in birds and contamination of egg collection equipment can directly contaminate eggs. Even when hens are vaccinated against Salmonella, the presence of breeding and young rodents shedding high numbers of organisms usually undermines vaccinal protection, although the occurrence of systemic infection of hens and internally contaminated eggs will still be reduced. When infected flocks are removed at the end of a production cycle, Salmonella can persist in the environment and infect replacement flocks. Intensive baiting of rodents before depopulation, and especially at the time when houses are empty and poultry feed has been removed, is essential to break the cycle of infection and avoid Salmonella carryover between flocks. Flies and litter beetles can also be infected for short periods and may be involved in the transmission and persistence of infection when downtime between flocks is short, or multiple age production is in place on the laying farm. Infestation by red mites can reduce the ability of birds to resist or clear infection, as a result of stress and anemia, and red mites are the main means of transmission of the nonzoonotic Salmonella Gallinarum biovar Gallinarum infection. Salmonella can survive for months in contaminated dust and laying hen houses tend to generate large quantities of dust during the long production cycle. Effective cleaning and disinfection between flocks is often costly to implement in laying houses, especially large cage units that are usually not designed to facilitate drainage after washing, leading to persistence of contamination between flocks. Removing all organic matter and using highly bioactive disinfectants such as aldehydes at the correct concentration and application rate is essential to avoid environmental persistence of Salmonella. Salmonella can be present at low prevalence in adult laying hens in mid lay and in older pullets and may therefore be difficult to detect. It is often assumed that new infections have entered laying farms when in reality the Salmonella has been continuously present but below the limits of detection of standard monitoring programs. Effective sampling and testing is therefore essential to the control of Salmonella on-farm. In the European Union, major progress on control of Salmonella in egg production has only been achieved after the introduction of effective vaccination programs and the application of severe financial penalties in terms of trade restrictions on the sale of fresh eggs from infected farms, which in many countries makes continued production from infected flocks economically unsustainable. Official sampling by the competent authority is also in place to validate operator sampling. Such incentives are usually required to ensure that effective control measures that come at a cost to the producer are fully implemented.

Keywords

Cleaning and disinfection; Laying hens; Risk factors; Rodents; Salmonella; Vaccines

1. Salmonella Control in Table Egg Production in Europe

In the European Union in 2014, 44% of the human cases of salmonellosis associated with a known food source were linked with eggs and egg products (EFSA, 2015). In Europe, the two Salmonella serovars that are specifically regulated in laying flocks in all Member States are Enteritidis and Typhimurium (EC, 2003), but in the Nordic Countries all serovars in poultry are subject to a slaughter policy, and Salmonella Kentucky, which has been spreading rapidly in poultry in some countries and is highly resistant to fluoroquinolones, has been added to National Control Programmes (NCPs) in France. The European Union level of prevalence of adult laying hen flocks that tested positive for Salmonella in 2014 was 2.54%. Salmonella Enteritidis was isolated from 0.7% of laying hen flocks and Salmonella Typhimurium from 0.2% (EFSA, 2015). S. Enteritidis has a special ability to colonize the ovary/oviduct of laying hens for long periods and therefore to internally contaminate eggs, and has been the most frequent serovar associated with egg-related foodborne outbreaks in Europe since the mid-1980s (Thorns, 2000). S. Typhimurium is a common cause of foodborne outbreaks in humans worldwide originating predominantly from cattle, pigs, and poultry (EFSA, 2010). Foodborne outbreaks related to the consumption of S. Enteritidis-contaminated eggs have been widely reported in Europe (Gormley et al., 2012; Harker et al., 2014; Liu et al., 2012; Zenner et al., 2013; Zielicka-Hardy et al., 2012), but have been decreasing since the introduction of harmonized monitoring and control programs in laying hens across Europe in 2008.

The role of S. Typhimurium in egg-related foodborne infections appears to be less significant than the one of S. Enteritidis (Martelli and Davies, 2011; Wales and Davies, 2011), except in Australia, where S. Enteritidis never became established in laying hens, since no infected primary breeding or parent stock was imported from either Europe or the United States.

Other Salmonella serovars can be linked to poultry products, egg contamination, and foodborne outbreaks (Okamura et al., 2001). For example, in the United States, Salmonella Heidelberg and S. Kentucky are frequently associated with eggs, broilers, turkeys, and poultry products and have resulted in large product recalls and outbreaks of food poisoning in the human population (Foley et al., 2011; Reddy et al., 2...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of Contributors
• About the Editors
• Preface
• Section 1. Salmonella in Egg Production Systems: International Prevalence, Issues, and Challenges
• Section 2. Salmonella Contamination in Layer Flocks: Pathogenesis, Dissemination, and Current Control Strategies
• Section 3. Development of Specific Interventions for Salmonella in Laying Hens and Table Eggs: Present and Future Prospects
• Index