Ovine Pasteurellosis Vaccine: Assessment of the Protective Antibody Titer and Recognition of the Prevailing Serotypes

Sheep husbandry is considered one of the most important activities in the socio-economic development in the Middle East region, especially in Iraq and Islamic Republic of Iran (IRI). Therefore this study was designed to evaluate the level of ovine pasteurellosis vaccine protective antibody titer and identification of the prevailing serotypes in Iraq (Basrah, Baghdad, Tikrit, Mosul, Erbil). The vaccine was made from pasteurella multosida Bio-type A and the serotypes of Mannheimia haemolytica. This investigation was performed from September ۲۰۲۱ to January ۲۰۲۲, in Iraq. Sheep blood sera samples were obtained from control unvaccinated and vaccinated sheep after ۱۴, ۲۱ and ۲۸ days post vaccination. The results showed that out of ۳۱۹ sheep blood sera samples which were evaluated using indirect Haemagglutination (IHA) test to detect Mannheimia haemolytica serotypes, the high prevalence (۱۰۰ %) of M. haemolytica A۲ was found in all the five study regions area, while ۹۶.۵ % was M. haemolytica A۷ and ۸۸.۱ % was M. haemolytica A۱. The level of antibody titer was measured by specific serum antibody titer of pasteurella multosida Bio-type A. The results revealed that out of ۲۶۸ vaccinated blood sera samples the overall antibody titer were ۱۲ (۳.۸ %), ۱۶ (۵%) and ۱۷ (۵.۳ %) for protective antibody titer of ۱:۱۶۰, ۱:۸۰ and ۱:۴۰ respectively and for antibody titer of ۱:۲۰ were ۱۵ (۴.۷%) and for antibody titer of ۱:۱۰ were ۱۷ (۵.۳ %), whereas the antibody titer in the control group was ۴ (۷.۸ %). The result of this study indicated that the vaccine administered has limited protective power against pasteurella multocida Bio-type A which lead to researchers for further study on identification of specific strain of pasteurella multosida and development of multivalent vaccine including the most prevalent pasteurella serotypes.

Keywords:

Sheep , Ovine Pasteurellosis Vaccine , Serotypes , Antibody titer