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The use of vaccines for the control of Salmonella in poultry

by 5m Editor
7 February 2005, at 12:00am

By the European Food Safety Authority - This article provides the summary and a link to a paper by the EFSA Journal on the Opinion of the Scientific Panel on Biological Hazards on the requests from the European Commission related to the use of vaccines for the control of Salmonella in poultry.

The use of vaccines for the control of Salmonella in poultry - By the European Food Safety Authority - This article provides the summary and a link to a paper by the EFSA Journal on the Opinion of the Scientific Panel on Biological Hazards on the requests from the European Commission related to the use of vaccines for the control of Salmonella in poultry.

SUMMARY

For more information on Salmonella in Poultry visit
www.Safe-Poultry.com


Vaccination Bottles
The existing Community legislation on food hygiene and control of zoonoses includes a number of provisions that seek to control and prevent the Salmonella contamination of foodstuffs. Targets for Salmonella spp. will be set progressively in different animal populations: breeding flocks of Gallus gallus, laying hens, broilers, turkeys and slaughter pigs. After each target is set, Member States will have to develop and submit national control programmes to the Commission for its approval. According to the Regulation, it may be decided to establish rules concerning the use of specific control methods in the context of the control programmes. The Regulation lays down that before proposing such rules on specific control methods, the Commission shall consult the European Food Safety Authority. The use of vaccines against Salmonella spp. is an example of such potential specific control methods.

The basis for successful control of Salmonella infections in poultry farms are good farming and hygienic practices (including all the aspects covering feed, birds, management, cleaning and disinfection, control of rodents etc.) as well as testing and removal of positive flocks from production. Vaccination of chickens is regarded as an additional measure to increase the resistance of birds against Salmonella exposure and decrease the shedding. Whether vaccination is a suitable option in a control programme or not, depends on the aim of control programme (reduction or eradication), type of poultry, stage of production, true prevalence of Salmonella, serovars targeted, detection methods used and cost-benefit.

The Salmonella vaccines currently authorized for use in poultry in the Member states have been authorised on the basis of the mutual recognition procedure. Both live and inactivated Salmonella vaccines are available. At the moment, the extent of vaccination of breeders and laying hens in different Member States differs considerably. The application of vaccines is recommended in some Member States and forbidden in others. Currently, broilers are only very seldom and turkeys not at all vaccinated in Europe. The vaccines are targeted for the most often reported serovars of human infections in Europe (S. Enteritidis and S. Typhimurium). However, vaccination is not, at the moment, a control option for many other serovars which can be present on poultry farms. Infection of poultry by serovars other than S. Gallinarum and S. Pullorum does not generally induce clinical signs except in young birds. Apart from these cases, vaccination has a limited effect on improving animal health and welfare and is used primarily for public health reasons (S. Typhimurium and S. Enteritidis).

Vaccines can decrease public health risk caused by Salmonella in poultry products by reducing the colonisation of reproductive tissues as well as reducing faecal shedding. There is experimental and some limited field evidence that a reduced level of faecal excretion and systemic invasion of Salmonella organisms in vaccinated birds will result in a reduced contamination of table eggs and the environment. However, further information is still needed on the level and on the duration of protection after vaccination under field condition.

When vaccination is used in Salmonella control programmes, possible interferences with standard Salmonella bacteriological and serological detection methods may be a disadvantage. In addition, there is concern over the use of antimicrobial resistance markers in some vaccines. One possible disadvantage of the use of live vaccines would be the spread of the strain to environment or to humans. Experience based on widespread use of existing Salmonella vaccines over several years and the results of monitoring, indicates that the vaccine strains of concern have not been disseminated in the environment or to humans. Use of inactivated vaccines against S. Enteritidis may also interfere with surveillance and control programmes for S. Pullorum/Gallinarum.

The panel concludes that if a control programme is targeting for serovars S. Enteritidis and S. Typhimurium in breeders of layers/broilers or laying hens and the flock prevalence is high, vaccination may be useful in reducing shedding and egg contamination. If the flock prevalence is low, vaccination may not be so useful but still could be used as one of the preventive measures to maintain a low prevalence. Provided that the detection methods are able to differentiate the vaccine strain from wild strains, both inactivated and live vaccines can be safely used throughout the life of the birds except during the withdrawal period before slaughter. This applies to parent flocks of layers and broilers; it can also apply to grand parents flocks of layers and broilers.

In order to reduce shedding by pullets, live and/or inactivated vaccines can be safely used. In order to reduce shedding and egg contamination by layers, only inactivated vaccines can be used due to the risk of spreading vaccine strain to eggs. Since vaccination cannot guarantee freedom of Salmonella, and the consequences of spreading from the top of the pyramid of poultry production would be severe, it is unlikely to be considered in great grand parents of layers and broilers.

If a control programme is targeting to eradicate the serovars S. Enteritidis and S. Typhimurium in breeders of layers/broilers or laying hens, vaccination is not an option since it does not eliminate the shedding. Furthermore, if a control programme is targeting serovars other than S. Enteritidis and S. Typhimurium in breeders, layers, broilers or turkeys, vaccination is not an appropriate option since the other serotypes are not covered by commercial vaccines available at the moment.

TABLE OF CONTENTS

SUMMARY
TABLE OF CONTENTS
BACKGROUND
TERMS OF REFERENCE
SUPPORTING DOCUMENTS
ASSESSMENT
  1. 1. BACKGROUND INFORMATION
    1.1. Epidemiology of non-typhoid salmonellosis in humans in Europe
    1.1.1. Serovars involved
    1.1.2. Types of food involved
    1.2. General Structure of poultry production
    1.3. Occurrence of
Salmonella spp. in poultry production
1.3.1. Breeding flocks of Gallus gallus (chicken, hens)
1.3.2. Laying hens and eggs for human consumption
1.3.3. Broiler flocks and broiler meat
1.3.4. Other poultry (excluding Gallus gallus)
1.4. Clinical Salmonella infections in poultry
1.5. Detection methods of Salmonella spp. in poultry
1.5.1. Bacteriological testing
1.5.2. Serological testing
1.6. Controlling Salmonella spp. in primary production
1.6.1. Biosecurity
1.6.2. Feed and Water Treatments
1.6.3. Competitive Exclusion
1.6.4. Probiotics and Prebiotics
1.7. EC approved Salmonella control programmes

2. VACCINES AVAILABLE FOR POULTRY
2.1. Scientific bases for vaccination
2.2. Serovars in vaccination and cross-protection between different serovars
2.3. Types of vaccines available for poultry
2.4. New vaccines in the future
2.5. Authorisation of vaccines in EU/National level
2.6. State of the art of vaccination in Member States

3. ADVANTAGES AND DISADVANTAGES OF THE USE OF VACCINES
3.1. Efficacy
3.1.1. Experimental studies
3.1.2. Field
3.1.3. Birds for meat
3.2. Safety for poultry and other animal species
3.3. Safety for humans
3.3.1. Vaccination of breeders and layers
3.3.2. Vaccination of birds for meat production
3.4. Environmental contamination
3.5. Gene exchange
3.6. Animal welfare

4. USE OF VACCINES IN CONTROL PROGRAMMES
4.1. Possible interference between Salmonella detection methods and vaccination
4.2. Possible inference between vaccination and other control measures
4.3. Vaccination at different stages of production line

5. CONCLUSIONS
6. RECOMMENDATIONS
7. REFERENCES
8. GLOSSARY SCIENTIFIC PANEL MEMBERS
ACKNOWLEDGEMENT

Further information

To read the full 74-page report, please click here (PDF)

Source: European Food Safety Authority - October 2004