Abstract:
Fowl cholera (FC) caused by Pasteurella multocida is among the serious infectious
diseases of poultry. Currently, formalin inactivated FC (FI-FC) vaccine is widely used in
Ethiopia. However, reports of the disease complaint remain higher despite the use of the
vaccine. The aim of this study was to develop and evaluate gamma-irradiated mucosal FC
vaccines that can be used nationally. In a vaccination-challenge experiment, the
performance of gamma-irradiated P. multocida (at 1 kGy) formulated with Montanide
gel/01 PR adjuvant was evaluated at different dose rates (0.5 and 0.3 ml) and routes
(intranasal, intraocular, and oral), in comparison with FI-FC vaccine in chicken. Chickens
received three doses of the candidate vaccine at 3-week intervals. Sera, and trachea and
crop lavage were collected to assess the antibody levels using indirect and sandwich
ELISAs, respectively. Challenge exposure was conducted by inoculation at 3.5×109 CFU/
ml of P. multocida biotype A intranasally 2 weeks after the last immunization. Repeated
measures ANOVA test and Kaplan Meier curve analysis were used to examine for
statistical significance of antibody titers and survival analysis, respectively. Sera IgG and
secretory IgA titers were significantly raised after second immunization (p=0.0001).
Chicken survival analysis showed that intranasal and intraocular administration of the
candidate vaccine at the dose of 0.3 ml resulted in 100% protection as compared to
intramuscular injection of FI-FC vaccine, which conferred 85% protection (p=0.002). In
conclusion, the results of this study showed that gamma-irradiated FC mucosal vaccine is
safe and protective, indicating its potential use for immunization of chicken against FC.
Keywords: chicken, fowl cholera, gamma radiation, mucosal vaccine, P. multocida
