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Efficacy of a Salmonella live vaccine for turkeys in different age groups and antibody response of vaccinated and non-vaccinated turkeys
Hesse et al. BMC Res Notes
Efficacy of a Salmonella live vaccine for turkeys in different age groups and antibody response of vaccinated and non-vaccinated turkeys
Martina Hesse 0
Andreas Stamm 0
Rita Weber 0
Gerhard Glünder 0
0 Clinic for Poultry, University of Veterinary Medicine Hannover , Bünteweg 17, Hannover , Germany
Objective: Human Salmonellosis continues to be one of the most important foodborne zoonoses worldwide, although a decrease in case numbers has been noted in recent years. It is a foodborne zoonotic infection most commonly associated with the consumption of raw egg products but also with meat consumption including the consumption of poultry products. Turkey flocks in Europe have been reported to be affected by Salmonella infection, too. The present study examines the efficacy of a newly licensed Salmonella life vaccine in reducing infections with the Salmonella serovars Typhimurium and Enteritidis in turkeys. Turkeys were vaccinated the first day of life and at the age of 6 and 16 weeks. Groups of birds which had received different numbers of vaccinations were then submitted to challenge trials with either SE or ST. Results: In vaccinated birds Salmonella counts in liver and spleen and, less effectively, in caecum were reduced compared to unvaccinated birds. In several groups serum antibody-titers were statistically significantly higher in vaccinated turkeys than in non-vaccinated ones at day seven post infection, but only in one out of six groups at day 14 post infection.
Salmonella; Turkey; Immunization; Antibody response
Introduction
Non-host-adapted Salmonellae usually colonize the
digestive tract of turkeys asymptomatically [
1, 2
].
Although in case of stress or at a very young age turkeys
may develop severe clinical signs [1], the most important
problem resulting from Salmonella infections lies in the
transmission to humans. The main source of food-borne
Salmonella outbreaks is the consumption of table eggs
and egg products, but single samples of fresh turkey meat
yielded the highest proportion of Salmonella-positive
results [
3, 4
]. Control strategies focus on hygiene and
management but also include vaccination [
5, 6
]. Despite a
recent decrease of the prevalence of human Salmonellosis
in several European countries it is still one of the most
important food borne zoonoses in Europe [
7, 8
].
Vaccination of turkeys might help to reduce prevalence in turkey
flocks and transmission to humans further. Barrow et al.
[9] stress that the use of vaccines has been empirical and
that immunological studies about Salmonella infections
in turkeys are still scarce, although certain aspects of
the humoral immune response have been studied before
[
10–12
]. In two recent studies we examined a bivalent
live Salmonella vaccine for its ability to induce primary
immune reactions after vaccination of 1 day old turkeys
[
13
] and for its protective efficacy in turkey poults against
Salmonella challenge infections at the age of 3 weeks
[
14
].The latter study found lower Samonella counts in
liver, spleen and caecum of vaccinated turkey poults
compared to unvaccinated poults in challenge trials at
3 weeks of age. No domination of either a TH1-response
or a TH2-response could be determined and no
statistically significant difference regarding the IgG serum
antibody response between vaccinated and non-vaccinated
turkeys after challenge infection was found.
The aim of the present study was to examine the
protective effect of the mentioned vaccine against
Salmonella Enteritidis (SE) and Salmonella Typhimurium (ST)
infections in turkeys in additional age groups and after a
different number of vaccinations. The efficacy was
determined by comparing bacterial counts in caeca, liver and
spleen after challenge. Since it has been shown that
turkeys do not produce antibodies from hatch it should also
be determined if birds which were older than the birds in
our former studies or which were vaccinated more often
would produce a notable serum antibody-response.
Main text
Materials and methods
Experimental design
At day of hatch 320 turkeys were housed separately and
divided randomly into two groups of 160 birds each. One
group served as non-vaccinated control group whereas
the other group was directly vaccinated with the
Salmonella live vaccine. Booster immunizations were applied
at the age of 6 and 16 weeks (Table 1). At 2, 6, 16 and
23 weeks of age challenge experiments were conducted
(Table 1). For each challenge experiment 20 vaccinated
and 20 non-vaccinated birds were infected with the
virulent SE strain and 20 vaccinated and 20 non-vaccinated
birds were infected with the virulent ST strain.
At day 7 and 14 post infection 10 individuals per group
were sacrificed by exsanguination after they had been
stupefied by manually applied blunt force trauma and
samples were collected. For vaccinated birds which were
infected with SE at 6 weeks of age only serum samples
d day of life, w w (...truncated)