Main challenges in poultry farming. Salmonellosis

Presentation brochure

MAIN CHALLENGES IN P

ULTRY FARMING

Salmonell sis Clara Marín Orenga Santiago Vega García

main challenges in poultry farming

Salmonellosis

MAIN CHALLENGES IN P

ULTRY FARMING

Salmonell sis Clara Marín Orenga Santiago Vega García

Authors: Clara Marín Orenga

and Santiago Vega García.

Format: 17 × 11 cm.

Number of pages: 70.

Number of figures: 66.

Binding: Paperback, wire-o.

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33 €

This handbook is entirely dedicated to avian salmonellosis based on a handy and visual approach of the topic. Being a critical public health issue, avian salmonellosis is a very important condition that should be acquainted for, controlled and prevented by every veterinary surgeon involved in the poultry industry. A handbook like this will help the experts understand, diagnose, treat and control this disease and thus contribute to maintain the animals’ and the final consumers’ optimum health status. Vaccination procedures are well described in order to provide the main guidelines to avoid vaccination failures and help controlling the prevalence and incidence. Issues like management control and biosecurity are also included to complete this practical guide on avian salmonellosis.

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Salmonellosis

Presentation of the book Avian salmonellosis is one of the most prevalent food borne diseases worldwide. Foodproducing animals, including laying hens and broilers, are the main reservoir of Salmonella infections, which have become a major issue to control and prevent in the food industry. Control measures are quite difficult to introduce since there are numerous potential sources of Salmonella infections and product contamination in integrated poultry farms, and require good management practices, strict sanitary measures and prophylactic strategies.

In order to fully understand the disease, the authors, renowned and prestigious experts in poultry, have built up this reference guide comprising practical graphic contents like pictures, flowcharts or graphs. The technical information this handbook develops has been organised in the classical way any infectious disease is usually described, starting with a thorough introduction and description of avian salmonellosis and its aetiology, followed by topics like epidemiology (describing the age or geographical distribution), pathogenesis, clinical manifestations, the latest and classical diagnostic techniques, and preventive and control measures.

The authors Clara Marín Orenga

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After graduating in Veterinary Science by the University CEU Cardenal Herrera in 2004, Dr. Marín Orenga earned a PhD by the same university in 2009. Since then, she has been a Professor at the Veterinary Faculty of the University CEU Cardenal Herrera.

Dr. Marín Orenga has participated in more than 18 investigation agreements with companies, associations and public organisms, which have resulted in publishing of 11 international papers (JRC), 25 national papers(general magazines), 2 books, 1 patent, 14 lectures in transference journeys and 44 participations in international and national seminars.

During this period she did investigation placements in the VLA (Veterinary Laboratories Agency) in Weybridge (United Kingdom), which is part of the DEFRA (Department for Environment, Food and Rural Affairs), in the reference Laboratory for Animal Health of the Ministry of Agriculture, Food and Environment of Spain and in the AHVLA (Animal Health and Veterinary Laboratories Agency) in Weybridge (United Kingdom). In January 2014, she was named European Diplomate for Poultry by the European College of Poultry Science.

Salmonellosis

Santiago Vega García PhD in Veterinary Medicine from the Complutense University of Madrid in 1999, Diploma in Health by the National School of Health Carlos III of Madrid in 1996, master’s degree in management of centres and social and health projects in 2010 and master’s degree in health and porcine production by the University of Lleida in 2011. He is currently the Dean of the Faculty of Veterinary Medicine of the University CEU Cardenal Herrera and member of the European and National Conference of Deans of the different degrees of health sciences.

He has formerly worked as head of the organization and development of the means of cultivation department of the Instituto Llorente S.A. of Madrid. He has organized and developed the laboratory of campaigns for the livestock sanitary of the regional agrarian laboratory of the community of Madrid.

He has performed stays at the department of virology of the central veterinary laboratory in Weybridge (United Kingdom) developing different diagnostic techniques in veterinary virology together with many other international stays in Italy and Hungary as well as Spain.

He has focused his research in two well defined lines, on the one hand in virology, specifically in the virus of bovine viral diarrhea and Border disease, West Nile virus and avian pneumovirus. As second-line he has studied diseases related to public health, (leishmaniasis, leptospirosis, salmonellosis, campylobacteriosis and ehrlichiosis) and possible zoonoses such as hepatitis E. This productive activity has resulted in several research projects obtained in public competition, the direction of various Diplomas of Advanced Studies (DEAs), and doctoral theses. He has maintained an active participation in congresses and national and international conferences as well as publications in conference proceedings; he also published monographs, book chapters and scientific articles in national and international journals. He has participated in numerous courses on virology, organized by different institutions.

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MAIN CHALLENGES IN P

ULTRY FARMING

Salmonell sis Clara Marín Orenga Santiago Vega García

Table of contents 1. Introduction General definition Synonyms

6. Immunity 7. Diagnosis

Economic significance

Diagnosis

History

Immunological techniques

2. Aetiology Salmonella spp.

Taxonomy

3. Epidemiology Hosts Age distribution Transmission Prevalence

4. Pathogenesis 5. Clinical manifestations Clinical manifestations Lesions

Bacteria isolation and identification Molecular techniques

8. Prevention and control Control through vaccination Available vaccines Hatchery vaccination Mechanism of protection Vaccination failure Management control Biosecurity Cleaning and disinfection Genetic control

References

7

Diagnosis

Salmonellosis

Molecular techniques Traditional methods for Salmonella spp. isolation, confirmation and serotyping are too laborious and time-consuming (Van de Giessen, 1996). In recent years, several advances in diagnostic technology have been developed and mean an important advance in infectious diseases studies. These molecular techniques are based on the Polymerase Chain Reaction (PCR) and are characterised by being simple, rapid and discriminative (Fernandez-Cuenca, 2004). The PCR name derives from one of its key components, a DNA polymerase used to amplify a piece of DNA by in vitro enzymatic replication. As PCR progresses, the DNA generated is used as a template for replication. This sets in motion a chain reaction in which the DNA template is exponentially amplified (Feder et al., 2001). With PCR it is possible to amplify a single piece of DNA across several orders of magnitude, generating millions or more copies of the DNA piece. PCR can be extensively modified to perform a wide array of genetic manipulations.

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Diagnosis

Using PCR at field level has several advantages such as speed of diagnosis and the high sensitivity of the technique. For proper control of the pathogen at the field level it is necessary to diagnose as quickly as possible. Using molecular techniques, the time for diagnosis of the bacterium is reduced from one week to a few hours (Fig. 30). Finally note that at present, molecular techniques (PFGE/RFLP/rt-PCR) allow a fast and reliable discrimination between the field and the vaccine strains of Salmonella spp., which greatly facilitates the study of the epidemiology of the bacterium under our production conditions.

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Figure 30. Molecular techniques are based on the Polymerase Chain Reaction.

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8

Prevention and control

Salmonellosis

Control through vaccination Vaccination is an effective tool for the prevention of Salmonella spp. infections by reducing the colonisation of reproductive tissues as well as reducing faecal shedding, and thus to decrease public health risk caused by Salmonella spp. in poultry products (Mastroeni et al., 2001). The main goal of vaccination is to reduce the susceptibility of poultry to Salmonella spp. infections, which will prevent/reduce the horizontal transmission within flocks, the vertical transmission of the infection to progeny of breeding flocks, the pathogen load in poultry house environments (and the likelihood of transmission to subsequent flocks), and the frequency of product contamination and disease transmission to consumers (Gast, 2007).

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Prevention and control

Available vaccines In the EU, different vaccines are currently available on the market to immunise commercial flocks against either S. Enteritidis (SE) or S. Typhimurium (ST); the choice therefore depends on which serotype protection is required. Some vaccines protect against both serotypes. Both live and inactivated vaccines have been used to protect birds against the infection (Fig. 31), and their use will depend on the market requirements as well as on the production conditions of farms (Gast, 2007). Traditionally, both vaccines are usually combined and used with this vaccination schedule: around weeks 1, 6 and 13 of rearing, live vaccines are administered to improve the humoral and cell-mediated immunity. Then, around weeks 16 and 18, an inactivated vaccine is administered to improve the humoral immunity.

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The currently available vaccines against salmonellosis can be broadly divided into three major classes: • live-attenuated vaccines, • inactivated vaccines, and • subunit vaccines.

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Figure 31. Inactivated and live vaccines in poultry production.

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Prevention and control

Salmonellosis

Live-attenuated vaccines Live-attenuated vaccines contain Salmonella strains with mutations or deletions of genes that are essential for their metabolism, virulence or survival in the host organism. The use of these strains has several advantages, which include an easy massive administration in the drinking water or by coarse spray (Fig. 32) and the induction of protective immunity through the activation of humoral and cell-mediated immune responses and unspecific defence mechanisms. They have been shown to induce both humoral and cell-mediated responses similar to those observed after natural infections (Sasai et al., 1997; Mastroeni et al., 2001), and present the benefits of ease of administration and low cost. Moreover, vaccinated chickens could excrete the vaccine strain after vaccination procedures and the vaccine may thus spread to susceptible birds in contact with vaccinated chickens or their manure. This indirect route helps poorly-vaccinated chickens to be properly immunised.

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Prevention and control

a

b

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Figure 32. Massive administration of the vaccine in the drinking water. (a) Hens and (b) broilers' breeders.

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8

Prevention and control

Salmonellosis

Inactivated vaccines Killed vaccines consist of whole bacteria inactivated by different methods including heat, formalin, acetone or other treatments. Inactivated Salmonella vaccines are usually administered parenterally, either intramuscularly or subcutaneously, and require at least two immunisations (Fig. 33).

These vaccines have been shown to induce strong antibody responses but poor cell-mediated immunity (Harrison et al., 1997).

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Figure 33. Intramuscular vaccination in poultry.

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Prevention and control

Subunit vaccines Subunit vaccines are composed of either a single antigen or multiple defined antigens (predominantly proteins) that are often present on the surface of bacterial cells and have important virulence characteristics. Most subunit vaccines are delivered via the intramuscular or subcutaneous route—unless they are formulated appropriately for oral delivery to minimise degradation of the protein antigen—and stimulate mucosal immunity (Fig. 34). Like inactivated vaccines, this type of vaccine lacks the regulatory and biological complications associated with live organisms (Barrow, 2007). On the other hand, subunit vaccines are usually poorly immunogenic, requiring formulation with appropriate adjuvants (Mutwiri et al., 2011).

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a

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b

Figure 34. (a) Subcutaneous and (b) oral vaccination: stimulation of mucosal immunity.

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8

Prevention and control

Salmonellosis

Hatchery vaccination Immunisation of young chicks during the first week of life is not as effective, as their immune system is not fully developed (Fig. 35). Therefore, vaccines that can transfer protective immunity to the progeny of breeder flocks may be required for the broiler industry (Van Immerseel et al., 2002; Beal and Smith, 2007). Presently, there are no bacterial vaccines available for in ovo delivery (Desin et al., 2013).

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Figure 35. Hatchery equipment for in ovo vaccination. Images courtesy of Hernández-Tramoyeres, 2015.

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Prevention and control

Mechanism of protection In chickens, vaccines should prevent intestinal and caecal colonisation resulting in reduced faecal shedding, and should be effective against systemic infection by preventing vertical transmission and egg contamination. The route of vaccination is important in influencing immune responses at the initial site of pathogen invasion where protection is more effective (Belyakov & Ahlers, 2011). In this context, mucosal dendritic cells play an important role in the induction and maintenance of protective immunity against pathogens such as Salmonella spp. They are responsible for antigen presentation following mucosal vaccination, and systemic immunisation has a limited effect on the delivery of the antigen to mucosal dendritic cells (Coombes & Powrie, 2008; Kelsall, 2008) (Fig. 36). Therefore, oral Salmonella vaccines provide an advantage over parenteral products as they are able to mimic natural infection and to stimulate both the mucosal and systemic immune responses (Husseiny & Hensel, 2005), whereas parenteral products are able to generate only systemic immune responses (Bouvet et al., 2002; Mastroeni et al., 2000) (Fig. 37).

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Prevention and control

Salmonellosis

Live-attenuated vaccine administered orally

Secretory IgA specific against Salmonella spp.

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Induction of specific IgA

Cytotoxic T-cell

Figure 36. Oral vaccination in poultry.

Dimeric IgA

Apoptotic cell

Th1

Macrophage

Figure 37. Mucosal protection and minimum inhibitory concentration (MIC) in the chicken gut provided by oral live-attenuated Salmonella vaccines. Adapted from Revolledo L and Ferreira AJP, 2012.

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Prevention and control

Vaccination failure The most common cause of vaccine failure is inadequate administraton of vaccines (Butcher & Yegani, 2008).

Before vaccinating, the whole process must be planned in detail, making sure all staff is trained in vaccine handling and application (Butcher & Yegani, 2008) (Fig. 38). A proper vaccination process will result in the improvement of disease control and performance of the birds (Butcher & Yegani, 2008).

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Figure 38. Proper handling for a correct administration of the vaccines.

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Prevention and control

Salmonellosis

Causes of vaccination failure (Fig. 39):

» Stress reduces the chickens’ ability to develop an immune response.

» Vaccinating sick birds is not recommended as their immune systems will not be functioning properly.

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» Certain infectious disease agents and mycotoxins are immunosuppressive and may result in vaccine failure.

» Poor management practices.

Figure 39. Inaccurate vaccination management practice.

Image courtesy of Hernández-Tramoyeres, 2015.

» The quality of the water used for drinking water vaccination is of crucial importance. The critical requirements with regard to water quality are pH level, absence of undesirable substances such as heavy metals, organic matter, high chlorine levels and residues of antibiotics, and a proper hygiene status.

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Prevention and control

Management control Many epidemiological studies have demonstrated the wide variety of routes by which Salmonella spp. can be disseminated within integrated poultry companies (Rose et al., 1999-2000; Heyndrickx et al., 2002; Davies & Breslin, 2003; Namata et al., 2008). Prevention of Salmonella spp. contamination in poultry products requires detailed knowledge of the most important sources associated with its presence in the production system (Slader et al., 2002) (Fig. 40).

a

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b

Figure 40. Biosecurity measures for bacterial control. (a) Poultry house disinfectant footbath. (b) Drive-through disinfection arch.

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Prevention and control

Salmonellosis

Biosecurity Biosecurity measures to control Salmonella spp. on commercial poultry farms include (OIE, 2015) (Fig. 41):

» a suitable location and construction of poultry establishments (considering the location of other poultry and livestock establishments, wild bird concentrations and the distance from roads used to transport poultry),

» implementation of an all-in-all-out, singleage-group rearing system,

» cleaning and disinfection of the poultry house and equipment,

» use of pelleted feed, » chlorination of drinking water, » restricted movement of birds,

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» proper litter management, » control of carrier vectors, » personnel hygiene measures, and » lack of contact with migratory birds.

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Prevention and control

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Figure 41. Biosecurity measures used to minimise the risk of Salmonella spp. entering the poultry farm.

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The publishing strength of Grupo AsĂ­s Editorial Servet, a division of Grupo AsĂ­s, has become one of the reference publishing companies in the veterinary sector worldwide. More than 15 years of experience in the publishing of contents about veterinary medicine guarantees the quality of its work. With a wide national and international distribution, the books in its catalogue are present in many different countries and have been translated into nine languages to date: English, French, Portuguese, German, Italian, Turkish, Japanese, Russian and Chinese.

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Servet works with the most renowned national and international authors to include the topics most demanded by veterinary surgeons in its catalogue. In addition to its own works, Servet also prepares books for companies and the main multinational companies in the sector are among its clients.

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