A SEROLOGICAL STUDY OF LACTOCOCCUS GARVIEAE IN EXPERIMENTALLY INFECTED CULTURED EUROPEAN SEA BASS (DICENTRARCHUS LABRAX L.)

Abstract

This study aimed to diagnose lactococcosis using different serological tests, such as slide agglutination, microwell agglutination, and ELISA, depending on the pathogenesis of this disease induced experimentally by Lactococcus garvieae in the European sea bass (Dicentrarchus labrax L.). For this purpose, 130 sea bass weighing 50-70 g and obtained from a private fish farm in the Aegean region were first subjected to the adaptation process and then used in the experimental infection study lasting for 50 days. After determining the LD50 dose to be used in the study, the L. garvieae ATCC 43921 strain with 10(8) cfu/ml was injected intraperitoneally to the fish in the experimental group (n-50), and infection was induced. Deaths were detected in the infected fish since the 8th day of the experimental study. While externally scoliosis in the infected fish and hemorrhage were observed around the eyes, abdomen and anus; pale liver, splenomegaly, enlarged heart, and hemorrhages in the internal organs were noted internally. Using different serological methods such as slide, microwell agglutination, and ELISA (Enzyme Linked Immunosorbent Assay), the level of antibody in the serum was measured, in addition to the diagnosis, from the beginning of the disease. In the present study, it was determined for the first time that L. garvieae formed the pathomorphological structure in the cultured sea bass depending on the course of the disease without creating latent infection and caused the disease by increasing the antibody level in the serum of the infected fish.