Experimental Lactococcus garvieae infection in rainbow trout, Oncorhynchus mykiss, Walbaum 1792: a comparative histopathological and immunohistochemical study

Abstract

The aim of this study was to induce Lactococcus garvieae infection in young and adult fish through different routes [intraperitoneal (IP) and immersion (IM)] and to investigate the pathogenesis and histopathological and immunohistochemical findings comparatively. For this purpose, a total of 180 rainbow trout (90 young, 20 ± 5 g and 90 adult, 80 ± 10 g) obtained from a commercial fish farm were used. The fish were divided into eight groups, four experimental groups (Young-Adult IP groups and Young-Adult IM groups, each contain 30 fish) and four control groups (Young-Adult IP Control groups and Young-Adult IM control groups, each contain 15 fishes). The experimental study was conducted using L. garvieae, and confirmatory identification was performed by PCR. The sequence result of the PCR amplicon of 16S rDNA from isolate L. garvieae LAC1 was determined and deposited in the GenBank database under accession number KC883976. Fish in the IP groups were intraperitoneally administered an inoculate containing 10(6) cfu mL(-1) bacteria 0.1 mL. In the IM groups, fish were kept in inoculated water containing 10(8) cfu mL(-1) bacteria for 20 min. Mortality as well as clinical and pathological findings was recorded daily, and significant differences in macroscopic and microscopic results were observed between the IP and IM administration groups. All tissue samples were immunohistochemically stained by the avidin-biotin-peroxidase complex and immunofluorescence (IF) methods using polyclonal antibody to detect L. garvieae antigens. In immunoperoxidase staining in the IP groups, positive reactions to bacterial antigens were most commonly seen in the spleen, kidney, heart, liver, peritoneum and swim bladder. In the IM groups, bacterial antigens were most commonly found in the eye, gill, spleen and kidney. In the IF method, the distribution of antigens in tissue and organs was similar to the reactions with immunoperoxidase staining. Finally, in this experimental study, an important correlation was seen between the distribution of L. garvieae antigens and lesions developing in many organ and tissues.

Determination of the muscle residue levels and withdrawal time of florfenicol in healthy and experimentallyLactococcus garvieaeinfected rainbow trout (Oncorhynchus mykiss, Walbaum 1792) grown in the Black Sea water

“…In the experimental study, infected fish with L. garvieae had clinical signs indicating the characteristic of lactococcus infection including bilateral exophthalmos, change in skin colour, fluid accumulation in the abdominal cavity, haemorrhages around the ocular area observed after 48 hr of incubation in infected fish with Lactococcus garvieae . The observed macroscopic findings were similar to those found in previous studies (Vendrell et al, ; Avci et al, ). Histopathological results were not found to be significant as they were seen in one fish from related groups and seen in both healthy and infected groups.…”

Histopathological changes of rainbow trout after experimental infection with Lactococcus garvieae

“…The mostly observed signs of the natural disease outbreaks in cultured rainbow trout are uni or bilateral exophthalmia, with periocular hemorrhages, loss of eye or eyes in some cases. Internal clinical signs of the disease include hemorrhagic fluid in the peritoneal cavity, pale liver, enlarged spleen and hemorrhages in the liver and muscle (Pereira, et al, 2004;Savvidis, et al, 2007); however, rainbow trout (80 ± 10 g) experimentally infected with L. garvieae via immersion route showed exophthalmia, paleness of the gills, hemorrhages in the liver, swim bladder peritoneum, muscle and bloody content in the intestine (Avci, et al, 2014). Many infectious agents produce typical tissue responses.…”

“…Histopathological examinations of rainbow trout which was infected with L. garvieae in culture conditions showed significantly lesions in the liver, kidney, spleen, gills, heart and stomach (Altun, et al, 2005;Didinen, et al, 2014). Avci, et al (2014)…”

Immunohistochemical evaluation of experimental Vagococcus salmoninarum infection in rainbow trout (Oncorhynchus mykiss, Walbaum 1792)

“…For the inactivated controls, 0.1 mL of sample was taken from the inactivated suspension and the inoculated tryptic soya agar (TSA) and incubated for 24 h at 22 °C (Uysal, Ciftci & Ciftci ; Avci et al . ).…”

“…This suspension was incubated at room temperature for 12 h under gentle agitation using a magnetic stirrer. For the inactivated controls, 0.1 mL of sample was taken from the inactivated suspension and the inoculated tryptic soya agar (TSA) and incubated for 24 h at 22°C (Uysal, Ciftci & Ciftci 2013;Avci et al 2014).…”