REPRODUCTION OF EDEMA DISEASE OF SWINE WITH PURIFIED SHIGA-LIKE TOXIN-II VARIANT

Twenty-one weaned Yorkshire-Landrace pigs were injected intravenously with graded doses of purified Shiga-like toxin-II variant (edema disease toxin). In a preliminary study, three pigs (Nos. 1, 2, 3) were injected with 48, 24, and 12 ng, respectively, of SLT-IIv/kg of body weight. Subsequently, three groups (Nos. 4, 5, 6) of six pigs each were injected with 6, 3, and 1.5 ng, respectively, of SLT-IIv/kg of body weight. Severe clinical signs and histologic lesions characteristic of edema disease developed in pigs Nos. 1, 2, and 3, and all six pigs in group No. 4. Eight of these pigs were euthanatized in extremis (mean time to death was 34 hours) and one died of the disease (52 hours). Moderate signs and lesions of edema disease were observed in all pigs in group No. 5, and three pigs were euthanatized (mean time to euthanasia was 42 hours). Mild signs and lesions were observed in three pigs in group No. 6. The most common gross pathologic changes were edema of the eyelids, submucosa of the stomach, and mesentery of the spiral colon and hemorrhage of the colon and cerebellum. Microscopic lesions were associated with vascular injury and included vessel necrosis, perivascular edema and hemorrhage, and superficial colonic and cecal erosions. The vascular lesions were observed in the cerebellar folia, submucosa and mucosa of the stomach, cecum, colon, and sporadically in the retina. None of the clinical signs associated with endotoxin were observed.