Submitted to: European Society of Veterinary Pathology
Publication Type: Abstract Only
Publication Acceptance Date: May 31, 1995
Publication Date: N/A
Materials: Pasteurella multocida toxin (PMT) reduces conchal bone formation and weight gain in growing pigs. In this study, twenty colostrum-dprived, Caesarean-derived pigs were divided into five groups (n=4/group) in order to determine the effect of PMT on chondrocytes of the proximal growth plate of the humerus. Group 1 received 0.1 cc PBS for 4 weeks; Group 2: 0.05 ug/kg PMT at 14 and 21 days; Group 3: 0.05 ug/kg PMT at 28 and 35 days; Group 4: PMT 0.1 ug/kg at 14 and 21 days; and Group 5: hyperimmune serum (from a sow given repeated injections of toxin) on days 13, 20, 27, and 34 and 0.1 ug/kg PMT on days 14, 21, 28, and 35. One hour prior to necropsy, pigs received bromodeoxyuridine (BrDU) IP. Turbinate perimeter ratio (TPR), physeal area, and BrDU immunoreactivity (BrDU-IR) of physeal chondrocytes were measured by computerized image analysis. Results: All pigs given 0.1 ug PMT without serum died from toxin, as did 4 pigs given 0.05 ug. Those pigs surviving 0.05 ug toxin had decreased weight gain and decreased TPR (conchal atrophy). These pigs also had reduced physeal areas and decreassed proliferation indices in physeal condrocytes based on BrDU-IR. Control pigs and serum-treated pigs gained weight, had no clinical effects, and had similar TPR, physeal areas, and cell proliferation indices. Discussion: This study demonstrates that PMT inhibits physeal formation by reducing chondrocyte proliferation in vivo. Hyperimmune serum neutralizes the effects of toxin on weight gain, clinical appearance, conchal growth, physeal area, and physeal chondrocyte proliferation.