Immunogenicity and Pathology of Formalin-Killed-Sepa <i>Salmonella Enterica Paratyphi A</i> Antigen in Pullet

Abstract

Intensive poultry production in Nigeria is currently on the increase with associated health challenges. This work investigated the immunogenicity of a documented Salmonella enterica Paratyphi A (SEPA) of poultry. A formalin-killed-SEPA containing 1x107cfu/ml was used as antigen. Seventy-five pullets were immunized orally with the antigen at 4 weeks of age and another 25 pullets (UC) served as unimmunized control. First and second booster doses were given at 10th and 29th day post-immunization (p.i). Three groups of immunized pullets (IA, IB, and IC) each of the 25 pullets were challenged with 0.5ml broth containing: >1x108cfu/ml SEPA (IA), 1x108cfu/ml Salmonella Gallinarum-(SG) (IB), while the immunized control group (IC) was fed with sterile broth. The unimmunized control group (UC) was infected with 1x108cfu /ml Salmonella enterica Paratyphi A. The formalin-killed vaccine of SEPA was immunogenic in poultry as indicated by the presence of O and H antibodies in the sera of pullets, producing protection only in pullets challenged with homologous strain, whereas morbidities and mortalities were recorded in unimmunized UC pullets challenged with homologous SEPA strain and IB challenged with heterologous strain (SG) during a 21-day experimentation. Also the inactivated-SEPA vaccine was able to protect birds against homologous challenge. These findings show that the inactivated-SEPA as a potential candidate vaccine offers protection of pullets against the emerging SEPA infection in pullets to avert severe economic losses in growing poultry industry and make the much needed animal protein available to feed the nation’s population.

Keywords: Salmonella enterica Paratyphi A, immunogenicity, vaccine, poultry.