Abstract

Comparative efficacy of Chitosan and oil adjuvanted Pasteurella multocida antigen in rabbits

Authors: Zareen Sajjad and Muhammad Shahid Mahmood

DOI: http://dx.doi.org/10.71081/cvj/2024.002

Abstract
Hemorrhagic septicemia (HS) is highly acute, fatal and bacterial disease mainly affecting water buffaloes and cattle, caused by Pasteurella multocida having higher incidence in younger animals, manifested by high fever, respiratory distress, salivation, nasal discharge, tongue protrusion, hot and painful swelling around throat region and edema in brisket. The successful prophylaxis regime includes the adjuvant-based vaccination of the animals. The present study was, therefore, planned to prepare and evaluate the comparative efficacy of two formulations of chitin derived chitosan adjuvanted hemorrhagic septicemia (HS) antigen and comparing its efficacy against oil adjuvanted HS antigen. Chitosan adjuvanted antigen was prepared by diluting 0.2% (W/V) chitosan in 25mM sodium acetate solution (pH 5.0) and adding suspension culture of Pasteurella multocida at 1:2 and 1:4 chitosan and similarly 1:2 mineral oil adjuvanted antigen was prepared. Sixty adult male rabbits randomly divided into four groups of 15 each with Group 1 kept as un-inoculated control. Group 2 rabbits were inoculated with 1:2 Chitosan-adjuvanted antigen through subcutaneous route and Group 3 were given 1:4 chitosan-adjuvanted antigen while Group 4 received 1:2 oil-adjuvanted antigen. Sera were collected at weekly interval post vaccination for seven weeks and titrated for antibody titers through indirect hemagglutination test. The results indicated that maximum IHA titers on day 28 post inoculation in Group 4 with the highest GMT of 294.06, followed by Group 3 (GMT= 256.0) and Group 2 (GMT=222.86). Moreover, the rabbits of Group 3 showed maximum antibody titer of GMT= 128.0 compared to the other two inoculated groups. The antibody titers remained higher (GMT=84.4) in Group 3, followed by Groups 4 and Group 2, respectively. Therefore, it was concluded that initially Group 4 oil-adjuvanted antigen imparted the highest antibody titer earlier than the Groups 3 and Group 2 and it dropped down rapidly till 42nd day post inoculation while Group 3 gained persistently higher antibody titer till 42nd day post inoculation. However, the protection against virulent Pasteurella multocida challenge, after four weeks post inoculation, was found equally better among all inoculated groups with 90% compared to un-inoculated control group.

Keywords: Hemorrhagic septicemia, Pasteurella multocida, Chitosan-adjuvant, Immunoprophylaxis, regime, GMT