Überprüfung der Verträglichkeit des Salmonella Typhimurium – Lebendimpfstoffes Salmoporc bei oraler Anwendung für drei Tage alte Saugferkel unter Berücksichtigung der Ausscheidung, Persistenz und Immunogenität des Impfstamms

Safety of Salmonella Typhimurium-live vaccine Salmoporc in oral
application in 3 day old piglets with consideration of elimination,
persistence and immunogenicity of the vaccine strain The aim of the
present study was to examine the Salmonella Typhimurium live
vaccine Salmoporc for its safety for 3 days old piglets applicated
by the oral route. Therefore Salmonella negative piglets were
vaccinated orally twice with a 10fold overdose of the vaccine when
the piglets were 3 and day 21 days old. In a second assay
investigations about the immunological response to this early
vaccination were made and spread and persistence of the vaccine
strain in different tissues were investigated. The piglets in this
group were vaccinated with a single dose of the vaccine also at day
3 and 21. In both cases negative control piglets within the same
age were given an equivalent amount of sterile physiological saline
solution orally. In both investigations, the faeces consistence,
body temperature, suckling frequency and general health were
evaluated in a period of time comprising 8 hours after vaccination.
Control of body weight and bacteriological examinations concerning
the shedding of the vaccine strain, were done weekly. Furthermore,
serological surveys concerning the immunological response to this
early vaccination were made. As a result of the 10fold overdosed
vaccination at day 3 and 21, an increase of the mean body
temperature was seen lasting 8 hours after vaccination. The number
of piglets showing a body temperature higher than 39, 8°C was
significant higher for the overdosed pigs at both time points. No
significance concerning clinical signs and suckling frequency were
observed between vaccinated piglets and the control group after the
first overdose. In a consequence of the 10fold overdosed
vaccination at day 21, a significant increase in respiration
frequency and lethargic behaviour as well a decreasing frequency of
suckling was seen within the piglets of the vaccination group. From
the fourth day after the overdosed vaccination until the end of the
tenth living week of the vaccinated piglets, a significant lower
mean body weight was measured in comparison to the control group.
After the single dosed vaccination on day 3 and 21 the piglets of
the vaccinated group had a significant higher mean body weight at
the time of weaning at the age of 4 weeks. A significant increase
in the occurrence of diarrhoea could be observed in both assays in
time course of 14 days after the first vaccination, as well as in
time course of 14 days after the second vaccination with one fold
dose of vaccine. After the ten fold overdosed vaccination, the
vaccination strain was detected in the faeces at latest at day 49
after the second vaccine application. In case of the one fold
vaccinated piglets, the vaccine strain was detected in faeces at
least until day 7 after the second vaccination. The colonization of
the internal tissues with the vaccine strain was timely restricted
until six weeks after the second immunization, as a sample of the
ileum and the colon have been found to be positive. The vaccine
strain was isolated in decreasing amounts from samples of the
ileoceacal lymph nodes, the ileum, ceacum content, colon, lung as
well as in samples of the liver and skeletal- and heart muscle.
Samples from the kidney were not found to be positive for the
vaccine strain at any time. Salmonella field strains could be
detected neither in the control nor in the vaccinated group in any
time during this study. A serological response in answer to the
single dosed vaccination on day 3 and 21 could be seen from day 7
after the second vaccination. A significant higher mean antibody
concentration in the serum of the piglets of the vaccinated group
could be detected from the third week after the second vaccination
until the end of the study after ten weeks. The maximum of the mean
antibody concentration was measured 49 days after the second
vaccination.