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 socioeconomic 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 biotype a and the serotypes of mannheimia haemolytica. this investigation was performed from september 2021 to january 2022, in iraq. sheep blood sera samples were obtained from control unvaccinated and vaccinated sheep after 14, 21 and 28 days post vaccination. the results showed that out of 319 sheep blood sera samples which were evaluated using indirect haemagglutination (iha) test to detect mannheimia haemolytica serotypes, the high prevalence (100 %) of m. haemolytica a2 was found in all the five study regions area, while 96.5 % was m. haemolytica a7 and 88.1 % was m. haemolytica a1. the level of antibody titer was measured by specific serum antibody titer of pasteurella multosida biotype a. the results revealed that out of 268 vaccinated blood sera samples the overall antibody titer were 12 (3.8 %), 16 (5%) and 17 (5.3 %) for protective antibody titer of 1:160, 1:80 and 1:40 respectively and for antibody titer of 1:20 were 15 (4.7%) and for antibody titer of 1:10 were 17 (5.3 %), whereas the antibody titer in the control group was 4 (7.8 %). 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.