Field Assessment of the Level of Protection Conferred by a Newly Prepared Combined Inactivated Vaccine against E. co li and P. multo cida in Rabbit in Egypt

Abstract

Pasteurellosis is the most prevalent, extremely contagious bacterial disease among domestic rabbits and is considered the leading cause of deaths in rabbits, resulting in enormous economic losses to the rabbit industry. Screening for bacterial agents causing mortalities in rabbits revealed the presence of Enterobacteriacae species in approximately 42% of studied cases, with E. coli the most commonly isolated organism. The present study was designed to evaluate the immune response of rabbits vaccinated with a locally prepared, combined inactivated vaccine of Pasteurella multocida and E. coli , adjuvanated with Montanide ISA70. A total of 370 rabbits, aged 2 - 3 weeks, were divided into four groups: (G1) vaccinated with a polyvalent P. multocida vaccine, (G2) vaccinated with a polyvalent E. coli vaccine, (G3) vaccinated with a combined inactivated Montanide ISA70 vaccine of P. multocida and E. coli , and (G4) kept as a non-vaccinated control group. All rabbits received two doses of 0.5 ml of the prepared vaccines, administered one month apart, and were then challenged with virulent strains of P. multocida and E. coli three weeks after the second vaccination. The prepared vaccines were evaluated by determining humoral immunity using indirect haemagglutination (IHA) test and ELISA. The potency of the vaccines was assessed through challenge and determination of LD50. Experimental findings on the prepared polyvalent combined inactivated P. multocida and E. coli vaccine indicated that it is a potent vaccine, producing the highest antibody titers and a 90% protection rate against challenges with virulent strains of P. multocida type A, D2, and E. coli types O157, O151 and O125. Thus, this vaccine is promising in addressing both P. multocida and E. coli problems in rabbits, farms, providing significant protection, and we recommend its commercial production to help rabbit producers control these two major bacterial infections.