Field efficacy of a recombinant toxoid vaccine against Shiga toxin 2e during a naturally occurring edema disease infection.

The objective of this field trial was to determine the efficacy of a recombinant toxoid vaccine against Shiga toxin 2e (Stx2e) in piglets suffering from edema disease (ED). Three farms with confirmed ED cases were selected for the field trials. On each farm, a total of 40 4-day-old pigs were randomly allocated to either the vaccinated or unvaccinated group, with 20 pigs per group (10 males and 10 females). A 1.0-mL dose of the recombinant toxoid vaccine was administered intramuscularly to pigs in the vaccinated groups in accordance with the manufacturer's recommendations at 4 d of age. A single 2.0-mL dose of phosphate-buffered saline was administered to unvaccinated pigs at the same age. Clinical signs of ED were observed in 12 piglets in the unvaccinated groups and 7 unvaccinated pigs died as a result of ED out of the total number of piglets on Farms A, B, and C. Vaccination had a positive effect on pig growth performance compared to that of unvaccinated pigs on 2 of the 3 farms. Seroconversion of neutralizing antibodies against Stx2e occurred in 70% of piglets in the vaccinated group on Farm A, 75% of vaccinated piglets on Farm B, and 55% of vaccinated piglets on Farm C, when detectable antibodies were measured at 17 d post-vaccination (dpv). Detectable antibodies were measured in 85% of vaccinated piglets on Farms A and B and in 90% of these piglets on Farm C at 37 dpv. These field trials determined that the ED recombinant toxoid vaccine successfully reduced clinical signs and mortality, improved average daily weight gain, and resulted in the production of neutralizing antibodies against Stx2e in pigs.