This study evaluated the use of an avirulent live Salmonella Choleraesuis vaccine to reduce the seroprevalence and number of Salmonella carrier pigs at slaughter. Seven batches of 500 pigs were included in each of the two study groups: the vaccinated group (VG) that was orally vaccinated and the control group (CG) that received a placebo on the first day of life. The groups were managed in a three-site system and followed up from birth to slaughter. Blood samples (n=378) were collected from each VG and CG to monitor the on-farm seroprevalence in both groups. Mesenteric lymph nodes and blood from animals (n=390) belonging to each group were collected at slaughter. At the first day of life, the seroprevalence in control batches ranged from 77.9 to 96.3 per cent, while in vaccinated batches, it ranged from 66.6 to 92.6 per cent. At weaning (21 days of age), the number of seropositives decreased in both groups (mean of 12 and 3.7 per cent for CG and VG, respectively). At slaughter, batches of VG had a significantly (P<0.0001) lower seroprevalence (46.6±5 per cent) and isolation of Salmonella from lymph nodes (33.1±5 per cent) compared with CG batches (79.7±4 per cent and 59.5±5 per cent, respectively). The results indicate that administration of a Salmonella choleraesuis-attenuated vaccine on the first day of life decreases Salmonella isolation and seroprevalence in pigs at slaughter.

Immunization with an avirulent live S choleraesuis vaccine has demonstrated consistent clinical and bacteriologic control of S choleraesuis infections in swine. Clinical signs, including febrile response, diarrhea and mortality, along with growth rate, are significantly improved (p<0.05). Pigs from one day of age and older may be safety vaccinated intranasally, or orally, via drinking water, against disease associated with S choleraesuis, and to reduce the culture prevalence and shedding of other serovars of Salmonellae (Nolan et al., 2000). Additionally, levels of the organism are effectively reduced in vaccinated, challenged pigs. Fecal shedding of S choleraesuis is significantly lower in vaccinated challenged pigs as compared to challenged control pigs. Organ culture prevalence is likewise dramatically lowered in vaccinated pigs. Vaccination at one day of age is at least as efficacious, and may offer even greater advantage over non vaccinated controls.

No abstract

This study was a randomized, blinded trial to evaluate effect of vaccine on post harvest Salmonella contamination rate of pig carcasses. Pig was the experimental unit. Litters were assigned to treatment by farrowing date and parity. Piglets were double tagged, sex recorded and entire litters were either vaccinated (oral drench) or left as non-vaccinated controls. No movement of piglets between treatments was allowed. At weaning, control litters were placed on the top level of a truck, vaccinated pigs on the bottom level, transported to a wean-finish barn, and mixed within pen at the wean-finish barn. At harvest, 100 animals per treatment were selected by random number and taken to a regional abbatoir. Pigs were loaded by treatment into separate compartments of a cleaned, disinfected trailer, transported three hours to the abbatoir, and held in adjacent cleaned, disinfected lairage pens overnight. Swabs for culture were taken from the transport vehicle and lairage pens. After CO2 stunning, exsanguination, and dehairing, individual pig numbers were written on each carcass in edible ink and the tags removed. The peritoneal cavity of each carcass was swabbed with an individual, sterile sponge hydrated in buffered peptone water, and the ileocecal lymph node was collected. Both were immediately sent to the Iowa State University Veterinary Diagnostic Laboratory for culture. The following morning, the surface of the chilled carcass was swabbed per the plant's USDA process (jowl, midline, tailhead) by the same method. Positive culture samples were serotyped at the National Veterinary Service Laboratory. Salmonella Anatum and S. Muenchen were isolated from two environmental pen samples. Salmonella Mbandaka was detected in lymph nodes of non vaccinated pigs. No Salmonellae were isolated from vaccinated pigs, a significant reduction from control pigs (Fisher's Exact P-value = 0.0332). Vaccination may be considered to improve the post harvest safety of pork.

The use of in-feed antimicrobials is coming under increased pressure in food animal production. Five field studies examined the impact of vaccines to stimulate protective immunity against pathogens commonly controlled with in-feed antimicrobials (Lawsonia intracellularis, a common enteric pathogen causing ileitis). Grow-finish pigs were immunized and various levels of infeed antimicrobials used to control or prevent Lawsonia were removed. Performance was compared between vaccinated and matched, continuously medicated barns. Performance was improved in vaccinated/reduced medication pigs while allowing for a 50% or greater reduction in in-feed antimicrobials targeting ileitis. More than six grams of tylosin and 20 grams of tetracycline per pig were removed from finishing feeds. Up to 50% of the time period in vaccinated finishing pigs occurred without any medications in feed. Large amounts of in-feed antimicrobials were successfully removed while improving growing and finishing pig performance.