CHARACTERIZATION OF S. GALLINARUM, S. PULLUROM AND S. ENTERITIDIS ISOLATED FROM CHICKEN IN CENTRAL ETHIOPIA AND EVALUATION OF PROTECTIVE AND CROSS PROTECTIVE EFFICACY OF SALMONELLA GALLINARUM 9R VACCINE AGAINST S. GALLINARUM, S. PULLUROM AND S. ENTERITIDIS
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Date
2015-06
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Abstract
Salmonellosis is one of the most important bacterial diseases of poultry with significant impact due to the loss of productivity in affected birds and its potential public health hazard. This study is performed with the aim of evaluating the immunizing and protective efficacy of the vaccine currently being used against salmonella strains precipitating disease outbreaks in poultry. Necropsy samples were collected from suspected cases showing typical pathological lesions for bacterial isolation. Isolation and identification of bacteria was carried out employing conventional bacteriological and biochemical methods followed by characterization using mPCR. Salmonella strains (12 Salmonella Gallinarum, 1 Salmonella Pullorum and 1 Salmonella Enteritidis) isolated from suspected cases were used for the challenge experiment in chicken vaccinated against salmonellosis at 42 days of age using 9R vaccine. Vaccinated chicken showing strong immune reaction as observed with slide agglutination test were challenged with field strains of virulent salmonella Gallinarum, salmonella Pullorum and salmonella Enteritidis strains (5 x 107 CFU/ml of each) 1ml orally at 14 days post vaccination. Post challenge follow-up for 2 weeks to determine the degree of protection of the vaccine showed that no mortality was observed in the vaccinated and salmonella Gallinarum challenged group despite that 3 (20%) chicken had pinpoint hemorrhages on the liver and enlarged spleen during post-mortem examination. However, in the non-vaccinated group, 8(53.3%) birds died, 5(33.3%) showed macroscopic lesions while the remaining 2(13.3%) had no any lesion. Observation of mortality and extent of lesion after challenge with the salmonella Pullorum virulent strain, showed no mortality in the immunized group while 2 (13.3%) birds died in the un-immunized group. One (6.7%) chick in the immunized group showed macroscopic lesion, while 13(86.7%) chicken showed post-mortem lesion in the un-immunized group. In salmonella Enteritides virulent strain challenge group, no mortality and macroscopic lesion were observed in vaccinated group, while postmortem lesion were observed with no mortality in 10(66.7%) chicken in the non vaccinated group. Assessment of the degree of protection showed that vaccination with live salmonella Gallinarum 9R strain significantly reduced the mortality and severity of infection due to salmonella Gallinarum and also provided remarkable cross-protection against salmonella Pullorum and salmonella Enteritidis challenge in tested birds.
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MSc Thesis
Keywords
Salmonella, post-mortem lesion, protective efficacy, challenge experiment