Efficacy of bi-valent whole cell inactivated bacterial vaccine against Motile Aeromonas Septicemia (MAS) in cultured catfishes (Heteropneustes fossilis, Clarias batrachus and pangasius pangasius) in Bangladesh

Abstract

The Motile Aeromonas Septicemia (MAS) is an important disease of cultured catfishes (Heteropneustes fossilis, Clarias batrachus and Pangasius pangasius), caused by different species of Aeromonas bacteria which have been documented to be higher death rates (≤70%) in Bangladesh since 2016. Present study was conducted to develop bi-valent vaccine using A. hydrophila and A. veronii, and to validate their efficacy via intra-muscular (IM) and oral-routes of immunization in selected species of fishes. Brood fishes of the three species were immunized with three doses of inactivated vaccine (10⁷ CFU /2.3 mg/ml). Hematological parameters of brood fishes and antibody levels (IgM) of broods, their larvae and eggs were determined by ELISA. Additionally, Relative Percent Survivability (RPS) and the IgM levels of the larvae after challenge with virulent A. hydrophila and A. veronii were also evaluated. Findings of this study showed that the lymphocytes, monocytes, granulocytes counts and antibody (IgM) titre of brood fishes, larvae and eggs from the vaccinated fishes were found significantly higher (p< 0.05) compared to the un-vaccinated control groups. Alternatively, antibody levels (IgM) in the larvae of vaccinated group of brood fishes fed with antigen coated feed was exhibited to be remarkably higher (p< 0.05) than the antigen non-fed group. The RPS of larvae of Shing (91.24 ± 2.00%), Magur (88.09 ± 2.88%) and Pangas (93.17 ± 1.52%) was found to be higher in the larvae at 20-day age of vaccinated group compared to non-vaccinated brood fishes group. Findings of this study indicated that the active immunization of brood fishes followed by oral immunization of their larvae feeding with antigen coated feed showed synergistic effect in protecting cultured Shing, Magur and Pangas fishes from frequent attack with Aeromonas spp at any age of their lifetime.

Keywords: ANOVA, Analysis of Variance; Aeromonas spp.; BAU, Bangladesh Agricultural University; BFRI, Bangladesh Fisheries Research Institute; Bi-valent vaccine; CFU, Colony Forming Unit; DMRT, Duncan’s Multiple Range Test; DPI, Days of Post-Immunization; EDTA, Ethylene Diamine Tetra Acetic Acid; ELISA, Enzyme-Linked Immunosorbent Assay; EUS, Epizootic Ulcerative Syndrome; IM, Intra-muscular; IgM; MAS, Motile Aeromonas Septicemia; Motile Aeromonad Septicemia (MAS); OD, Optical Density; PCR, Polymerase Chain Reaction; RPS; RPS, Relative Percent Survivability; Shing, Magur and Pangas; TPC, Total Plate Count; TSA, Trypticase Soy Agar.

Fig. 1

Level of serum antibody (IgM) in immunized brood Shing, Magur and Pangas fishes at 7, 21 and 35 days of post vaccination.

Fig. 2

RPS of larvae produced from the immunized brood Shing, Magur and Pangas fishes and control group after challenged with A. hydrophila and A. veronii at larvae aged 5, 10, 15 and 20 days of hatch. T1, Larvae from immunized brood fish followed by fed with feed-based bi-valent vaccine; T2, Larvae from immunized brood fish with non-fed vaccine.

Fig. 3

Antibody (IgM) level of eggs and larvae homogenates at age 5, 10, 15 and 20 days from three times immunized and non-immunized brood fishes. T1, Larvae from immunized brood fish followed by fed with feed-based bi-valent vaccine; T2, Larvae from immunized brood fish with non-fed vaccine and T3, larval group from the non-immunized group (control).