Vaksin bivalen untuk pencegahan penyakit Motile Aeromonas Septicemia dan Streptococcosis pada ikan nila (Oreochromis niloticus)

Abstract

Etiological agents of common fish diseases are the Gram-negative Aeromonas hydrophila and the Gram-positive Streptococcus agalactiae, both are considered severe fish pathogens on account of their ability to cause damaging disease outbreaks in Nile Tilapia (Oreochromis niloticus). The occurence of co-infections between A. hydrophila and S. agalactiae at Waduk Cirata was about 20% per populations. Clinical signs appeared soon after infection, and include depression or excitability, anorexia, C-shaped body posturing, erratic swimming and whirling, and death. Aeromonas hydrophila and S. agalactiae cultures were not able to inhibit each other and showed negative results from antimicrobial activity, both are succeptible to antibitoics Tetracycline and Chloramphenicol. Nile Tilapia also were clinically examined and necropsied for histopathology, samples were taken from kidney, brain, liver, and spleen. Histopathological lesions were grouped into two characteristic patterns. The first pattern consisted focal lesion and inflammation. The second pattern consisted of multifocal lesion, necrotic, and inflammatory lesions resulting organ deformation. The mortality patterns of Nile Tilapias showed acute and chronic infections to Motile Aeromonas Septicemia, sub-acute infection to Streptococcocis. There was a homeostatic balances on hematological respons during co-infection. Aeromonas hydrophila AHL0905-2 and Streptococcus agalactiae N14G, were used as an inactivated A. hydrophila and S. agalactiae vaccine. Different vaccine preparations and formulations for vaccination of Nile Tilapia species were tried by adding neutral buffered formalin 3% to the bacterial culture (bacterin). The safety of formalin inactivated vaccine is still questionable by some aquaculture practitioners, but the sterility and safety test results of the bivalent vaccine was safe to use through intraperitoneal injection route. An antibody response was detected at the 1st week that rose significantly (p<0.05) at the 3th week post immunization in all the immunized groups. Similarly, there were significant difference (p<0.05) in the humoral immune response between groups immunized with single and mixed bacterial antigens. Upon challenge with single pathogen, a high relative percent survival was recorded in the group immunized with mixed bacterial antigens and was comparable to those fish immunized with the single bacteria. The value of relative per cent survival from bivalent vaccine mixed whole cell+ECP was 100% and 86.2% to single infections and 56.7% to co-infections, indicate that this vaccine was eficient in Nile Tilapia.