Browsing by Author "Dr. Nick Nwankpa"

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    COMPARATIVE STUDY OF THE STABILITY AND IMMUNOGENICITY OF INACTIVATED BACTERIN, ALUM PRECIPITATED AND OIL ADJUVANTED HEMORRHAGIC SEPTICEMIA VACCINE
    (2018-06) Hassen, Belay; Dr. Nick Nwankpa; Dr. Bedaso Mammo, Dr. Fufa Daewoo
    Haemorrhagic septicaemia (HS) is the most devastating disease of cattle and buffalo particularly to smallholder farmers where husbandry and preventive practices are poor. Due to the acute nature of the disease and the presence of carrier animals after recovery, vaccination is considered as the only efficient method of controlling the disease. Although alum precipitated vaccine is the most widely used; it has come across drawbacks including poor stability and weak immune response. Oil adjuvanted vaccine on the other hand has been emerging with better stability, longer periods of protection and stronger immune response. Therefore, this experimental study was conducted with the objectives of comparing the stability and immunogenicity of inactivated bacterin (IBV), alum precipitated (APV) and oil adjuvanted (OAV) HS vaccine candidates. To achieve this, Pasteurella multocida B:2 (Ethiopian isolate) was grown on tryptose soy broth (TSB) supplemented with 10% horse serum, inactivated with formalin (0.5%) and the turbidity was standardized to contain 1.5mg antigen/ml. APV was prepared by admixing aluminium potassium sulphate (1%) with the bacterin whereas OAV was prepared by mixing the bacterin with equal volume of Montanide ISA 61 VG. The inactivated culture was used as IBV. The three vaccine formulations were stored at 4ºC and tested for stability (potency and identity) once a month for 5 months. Potency test was conducted on mice while test for identity was conducted using polymerase chain reaction. On the other hand, nine calves were divided into three groups, each group vaccinated with each candidate and boosted on day 28 post primary vaccination. Sera were collected on days 0, 28, 42 and 56 to assess the immune response. The IBV and APV showed retention of stability when stored at 4°C for 30 days. The potency dropped to 0.2 log10 and 0.8 log10 for IBV and APV respectively when storage period was extended to 60 days whereas there was no difference between vaccinated and unvaccinated groups when both formulations were stored for 90 days. OAV retained stability when stored at 4°C for 90 days and potency dropped to 0.6 log10 and 0.2 log10 when storage was extended to 120 and 150 days respectively. Application of indirect hemmaglutination test on sera obtained from calves revealed that OAV induced stronger immune response with peak antibody titre of 3.4 log10 on day 56 while APV induced protective, but, relatively weaker immune response with peak antibody titre of 2.4 log10 on day 56. The IBV induced weak immunity (1.5 log10 on day 56) indicating the need for incorporation of a suitable adjuvant. There was a significant difference in the immune response between the vaccine groups (P<0.05, ANOVA). Therefore, this study revealed the weak stability as well as immunogenicity of the conventionally used alum precipitated vaccine and urges the need to produce oil adjuvanted vaccine for the control of the disease.