Reduced mortality and morbidity associated with verotoxin 2e-induced edema disease in pigs using a recombinant verotoxin 2e vaccine

Abstract

Objective: The efficacy of Vepured, a recombinant verotoxin 2e (VT2e) vaccine, against clinical signs and mortality of VT2e-induced toxemia was evaluated in a controlled experimental challenge. Materials and methods: Piglets free of VT2e neutralizing antibodies (NAb) were selected and blocked by weight and litter and randomly allocated between three groups: vaccinated (n = 32); non-vaccinated (n = 32); and non-vaccinated, non-challenged (n = 10). Piglets were vaccinated intramuscularly with 1 mL of Vepured (vaccinated) or phosphate-buffered saline (non-vaccinated) at two days of age. The onset and duration of protection were investigated via intravenous VT2e challenge, using mortality and clinical signs related to VT2e-induced toxemia. Results: Mortality in the non-vaccinated piglets was 92.3% and 68.8% at the onset of immunity and through the experiment duration, respectively, whereas all vaccinated piglets survived the challenge. The total clinical score and percentage of animals with clinical signs were greater (P < .05) in the non-vaccinated group. Also, vaccinated pigs had better growth performance than non-vaccinated pigs. Neutralizing antibodies against VT2e were detected in most (78.6%) vaccinated piglets at 21 days and in all vaccinated piglets at 28 days and mean NAb titers (log2) were 3.9 and 4.3, respectively. Moreover, NAb persisted for at least 112 days in most (94.1%) vaccinated animals (mean NAb titer was 3.8). Implications: In this study, active immunization with Vepured conferred effective protection against VT2e-induced toxemia, reducing the presence and severity of clinical signs and preventing mortality related to VT2e-induced toxemia from 21 to 112 days after vaccination.