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Bacterial isolation Lesions from skin, fin and gill, were inoculated onto Trypticase Soy Agar (TSA) (Merk, Germany) and incubated aerobically at 28°C for 24 h. Then internal samples were acquired alike aseptically from the kidney, liver, spleen and the infected muscles. The plates were examined for bacterial growth. Dominant colonies were selected, re-streaked on Trypticase Soy Agar (TSA). Cultures were placed in 20% glycerol and supplemented in Trypticase Soy Broth (TSB) for storage at-80°C. Dominant colonies were selected for bacterial isolation to establish the optimal number of bacterial cells, and undergoing thorough purification procedure until pure colonies were established to be sure that dominant colonies were not contaminated.

This study was conducted on 48 male Sprague Dawley rats to determine the immunological responses of experimental adjuvanted vaccines of Mannheimia haemolytica A2 (M. haemolytica A2) injection and to observe their protection level upon live M. haemolytica A2 challenge. Fortyeight clinically healthy Sprague Dawley rats were divided into four groups; Groups 1 and 2 were vaccinated intramuscularly and intraperitoneally, respectively, with an Exo-Polysaccharide (EPS)-adjuvanted vaccine prepared from formalin-killed M. haemolytica serotypes A2, Group 3 with formalin killed M. haemolytica seed. At the same time, Group 4 received intraperitoneally Phosphate Buffer Saline (PBS) as a control. After the first vaccination dose, Groups 1,2, and 3 showed a gradual increase in IgM, IgG, and IgA levels significantly (p<0.05). However, their level started to decline six weeks post-vaccination, indicating that the booster dose was needed. Upon the delivery of the second booster dose, antibodies titer showed a persistent increase significantly (p<0.05), especially the serum IgG level. All groups were challenged with live virulent Mannheimia haemolytica A2 after the level of antibodies declined twice after the second booster was delivered. No rat deaths were found in the Combined EPS -M. haemolytica adjuvant vaccine after 14 days following the challenge (0%). In unvaccinated rats, higher mortality and morbidity were noted (100%) and less was reported in rats receiving M. haemolytica A2 Vaccine seed (8%). Histologically at two weeks, post-challenge revealed negligible lung lesions in groups 1 and 2 and mild lesions in group 3. Lung lesions were recorded in all unvaccinated control rats. Furthermore, M. haemolytica A2 re-isolated successfully from lung samples in groups 3 and 4. In conclusion, Rats receiving adjuvant-M. haemolytica vaccine confers reasonably high preventive efficacy compared to M. haemolytica A2 by itself. Further studies should be conducted on measuring the antibody titer in different vivo, such as goats or sheep.

Background and Aim: Pneumonic mannheimiosis (PM) is a common respiratory bacterial disease among small ruminants. Despite numerous management methods, vaccination remains a suitable strategy to combat or reduce PM in goats and sheep. Thus, a study was conducted in Malaysia to evaluate the immunogenicity of exopolysaccharide-adjuvanted Mannheimia haemolytica A2 vaccine (EPS-MHA2) under laboratory and field conditions for its potential use as an efficient vaccine against PM. Materials and Methods: This study induced immunoglobulin (Ig) responses following intramuscular (IM) delivery of the EPS-MHA2 vaccine on 12 goats for about 7 months. Goats were divided into three groups, with three goats per group, and they were vaccinated intramuscularly as follows: Group 1 was vaccinated with an adjuvanted vaccine prepared from formalin-killed M. haemolytica serotypes A2 and EPS excipient; Group 2 was vaccinated with formalin-killed M. haemolytica seed only, whereas Group 3 was injected with phosphate-buffered saline (PBS) as the negative control. Measures of specific immunity included serum IgM, IgG, and IgA as well as bronchoalveolar lavage fluid secretory IgA and the size and number of the bronchus-associated lymphoid tissue (BALT). Results: From the 1st day of vaccination, Groups 1 and 2 showed a significant (p < 0.05) increase in serum IgM, IgG, and IgA levels. However, the antibodies started to decline 5-week post-vaccination, indicating that the booster dose was necessary. On the second exposure to the same vaccine (booster), the level of antibodies showed a significant increase (p < 0.05), particularly IgG. All groups were challenged intratracheally by virulent MHA2 2 weeks after the decline of second antibodies on the administration of booster. All goats were euthanatized and necropsied 4-week post-challenge. The number and size of the BALT in Group 1 goats significantly increased compared with those in Group 2 and the unvaccinated control. Bacteriological parameters were evaluated, in which MHA2 was reisolated successfully from lung samples in Group 3. The IgA level produced by the group vaccinated with EPS-MHA2 was significantly (p < 0.001) higher than that the MHA2 vaccine and PBS groups. All data obtained were analyzed statistically using a one-way analysis of variance. The results indicate that IM injection of EPS-MHA2 vaccine significantly enhanced the immune response against MHA2. Conclusion: Therefore, the addition of EPS to MHA2 (EPS-MHA2 vaccine) can effectively protect goats from lethal mannheimiosis infection. Factors such as the ideal concentration of EPS should be further studied to verify its application potential as a vaccine adjuvant, and the extraction of EPS from different microalgae species should be further investigated. This study showed a novel and exciting set of data and a vaccination system, in which the suppressive effects of mannheimiosis may be further investigated.