Ultrastructural Changes and
Bacterial Localization in
Buffalo
Calves Following Oral Exposure to
Pasteurella multocida B:2
M.S. Abubakar, M. Zamri-Saad*
and S. Jasni
Department of Veterinary
Pathology and Microbiology, Faculty of Veterinary Medicine,
Universiti Putra Malaysia, 43400 Serdang, Malaysia
*Corresponding author: mzamri58@yahoo.com
Abstract
This study describes the
ultrastructural changes and distribution of
P. multocida B:2 in the respiratory
and gastrointestinal tracts of buffalo calves following oral exposure and
compared with intratracheal exposure. Nine 8-month old buffalo calves were
divided into 3 groups. At the start of the experiment, dexamethasone (1mg/kg)
was injected intramuscularly into buffaloes of all groups for three consecutive
days. Then, calves of Group 1 were exposed orally to 50ml of the inoculum
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 of Group 3 were
exposed orally to PBS. Transient and mild clinical signs were observed in calves
of Groups 1 and 2. Pasteurella multocida
B:2 was isolated from the nasal mucosa for up to 5 days post-infection. Only
calf that was killed at 48 h post-infection had
P. multocida B:2 in both respiratory
and gastro-intestinal tracts showing ultrastructural changes typical of acute
cellular injury, with degeneration of endothelium and vascular walls. There were
deciliation in the respiratory and microvilli degeneration in the
gastrointestinal tracts. The study concludes that oral exposure 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.