Ultrastructural Changes and Bacterial Localization in Buffalo Calves Following Oral Exposure to Pasteurella multocida B:2

This study describes the ultrastructural changes and distribution of p. multocida b:2in the respiratory and gastrointestinal tracts of buffalo calves following oralexposure and compared with intratracheal exposure. nine 8-month old buffalocalves were divided into 3 groups. at the start of the experiment, dexamethasone(1mg/kg) was injected intramuscularly into buffaloes of all groups for threeconsecutive days. then, calves of group 1 were exposed orally to 50ml of theinoculum containing 109 colony-forming unit (cfu)/ml of live p. multocida b:2.calves of group 2 were exposed intra-tracheal to the same inoculum while calves ofgroup 3 were exposed orally to pbs. transient and mild clinical signs wereobserved in calves of groups 1 and 2. pasteurella multocida b:2 was isolated fromthe nasal mucosa for up to 5 days post-infection. only calf that was killed at 48 hpost-infection had p. multocida b:2 in both respiratory and gastro-intestinal tractsshowing ultrastructural changes typical of acute cellular injury, with degeneration ofendothelium and vascular walls. there were deciliation in the respiratory andmicrovilli degeneration in the gastrointestinal tracts. the study concludes that oralexposure may not play major role in the development of hemorrhagic septicemia.nevertheless, the buffalo calf that succumbed to hemorrhagic septicemia carried p.multocida b:2 in the gastro-intestinal organs.