ISOLATION, PREPARATION AND EFFICACY TRIAL OF ADJUVATED FORMALIN INACTIVATED FOWL CHOLERA VACCINE FROM LOCAL ISOLATES OF PASTEURELLA MULTOCIDA IN LAYER CHICKENS
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Date
2008-06
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Abstract
Crossectional and experimental studies were undertaken with the objectives of isolating, producing and efficacious trials of adjuvated formalin-killed fowl cholera vaccine from local isolates of P. multocida on layer chickens at the Department of Vaccine Production and Microbiology laboratory of the National Veterinary Institute in collaboration with Addis Ababa University, Faculty of Veterinary Medicine between September 2007 and May 2008. The study used 384 chickens having typical clinical signs of fowl cholera from commercial poultry farms and backyard poultry to detect P. multucida. A total of 300 Bovans Gold-line breed layer chickens were used for the experimental trial. A total of 3 local isolates of Pasteurella multocida (Kombolch state farm, Genesis Farm and Tadesse Farm) were identified and characterized from the natural fowl cholera out-breaks. The best growth of the isolates was in the dextrose starch agar with 5% chicken serum. All the isolates were studied for their virulence in chickens at the age of 4 weeks and found that Kombolcha State Farm isolate was highly virulent with a mortality of 100% and mortality rate of 2 chicken-day-at risk, followed by Genesis Farm isolate with a mortality of 90% and a mortality rate 1.63 chicken-day -at risk. The least virulent isolate was from Tadesse Farm, which showed no mortality. Three adjuvanted (Montanide ISA 50, Al (OH) 3 and AlK (SO4) 2) formalin inactivated fowl cholera vaccines were prepared using three doses of bacterial loads (106, 109and 1012) from Kombolch State Farm isolate. The efficacy performances of these vaccines were evaluated and compared with each other. There were significant differences in geometric means of the antibody IHA titers between bacteria doses of 106, 109and 1012. The dose level of 1012 CFU elicited highest antibody response followed by 109 and 106. The three kinds of adjuvants used did not significantly differ in levels of immune responses. This study found that there was association between IHA log10 titers with bacteria doses (loads) and adjuvants. The linear regression indicated that the IHA log10 titers were associated with bacterial doses used. Multivariable correlation matrix showed very strong associations between IHA log10 titers and bacteria loads (r = 0.729). This correlation was significant. The experimental challenge protection test indicated that double doses of Aluminium potassium sulphate and Montanide ISA 50 adjuvanted vaccines gave better geometric mean antibody IHA titers and better protection (PI= 91.6% for both vaccines) as compared with aluminium hydroxide adjuvanted vaccine with PI = 83.9%. In the unvaccinated control groups 86% of mortality was recorded. This study
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indicated that AlK (SO4) 2 adjvanted vaccine at a bacterial dose of 1012 gave better IHA titers in comparison with other adjuvant and bacterial load vaccines. Although inactivated fowl cholera vaccines have been produced in other countries, the poultry enterprises in Ethiopia continue to experience problems associated with the disease due to unavailability of cost-effective vaccines. To alleviate this problem, the adaptation of this technique used in this trial with eventual production of the vaccines at the National Veterinary Institute is highly recommended.
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Keywords
Fowl cholera, Formalin inactivated, adjuvant vaccine, bacterial load