Pathological and immunohistochemical studies following the experimental infection of ayu (Plecoglossus altivelis) by Edwardsiella ictaluri

Abstract

In recent decades, several mass mortalities were recorded in riverine ayu (Plecoglossus altivelis) in Tokyo Metropolis, Hiroshima Prefecture, and Yamaguchi Prefecture, Japan; in these outbreaks, microbiological and pathological examinations revealed Edwardsiella ictaluri as the causative agent. In this study, histopathological findings and immunohistochemical localization of the bacteria following experimental infection of ayu were discussed. Infection experiments were performed using 44 healthy cultured ayu fingerlings using E. ictaluri isolate (H90). The fish were injected with the isolate intraperitoneally with a dose of 5.1 × 105 cfu/fish, while the control fish were injected with sterile phosphate buffered saline. The fish were observed for clinical signs, with daily collection of dead fish, and isolation of bacteria from the posterior kidney was performed and confirmed to be E. ictaluri by slide agglutination using anti‐PH0744 serum. Daily collection of five moribund fish for necropsy and tissue specimens collection from hepatopancreas, spleen, posterior kidney, gills, brain, heart, and intestine for histopathological and immunohistochemical examination. Post‐mortem lesions were recorded as exophthalmia, bloody ascitis, hemorrhagic kidney and distended gallbladder, meningio‐encephalitis, hemorrhagic vent, and petechial hemorrhages on viscera. Histopathological examination revealed diffuse severe congestion in blood vessels and several degenerative and necrotic changes inconcurrent with positive antigenic staining by immunohistochemistry.

Edwardsiella ictaluri: A systemic review and future perspectives on disease management

“…24,98 Histopathological examinations in most susceptible hosts revealed similar results such as granulomatous inflammatory reactions, necrosis, haemorrhage, pyknosis and karyorrhexis in internal organs, epithelial lining hyperplasia in gills and observation of clumps of rod-shaped bacteria in tissues (Figure 4). 12,39,97,99 Electron transmission microscopy also revealed the intracellular localization of E. ictaluri in macrophage in infected zebrafish head kidney tissue (Figure 5).…”

“…20,23,57,96 E. ictaluri-infected fish such as catfish (channel, striped and yellow) and ayu exhibit external gross clinical signs such as skin haemorrhage and ulceration, distended abdomen, discoloration, reddened anus, exophthalmos and meningioencephalitis (red head) (Figure 2). 23,24,57,97 The general internal clinical signs reported in the susceptible hosts that include catfish and tilapia and ayu are white nodule granulomas, abdomen ascites, pale gills, enlarged gallbladder, reddened gonads and enlarged and haemorrhagic posterior kidney (Figure 3). 12,23,39,97 Both channel catfish and yellow catfish display classic 'hole in the head' lesion whilst yellow catfish additionally display the 'hole-under-thejaw' lesion.…”

“…23,24,57,97 The general internal clinical signs reported in the susceptible hosts that include catfish and tilapia and ayu are white nodule granulomas, abdomen ascites, pale gills, enlarged gallbladder, reddened gonads and enlarged and haemorrhagic posterior kidney (Figure 3). 12,23,39,97 Both channel catfish and yellow catfish display classic 'hole in the head' lesion whilst yellow catfish additionally display the 'hole-under-thejaw' lesion. 24,98 Histopathological examinations in most susceptible hosts revealed similar results such as granulomatous inflammatory reactions, necrosis, haemorrhage, pyknosis and karyorrhexis in internal organs, epithelial lining hyperplasia in gills and observation of clumps of rod-shaped bacteria in tissues (Figure 4).…”

The State-of-the-Art Antibacterial Activities of Glycyrrhizin: A Comprehensive Review

“…However, with the emergence of drug resistance, the inhibitory effect of some pathogenic bacteria on antibiotics gradually diminishes or even disappears. Therefore, it is necessary to discover new therapeutic agents that can effectively inhibit bacterial diseases [ 8 ]. Meanwhile, the research and development of broad-spectrum drugs is also underway, and the control of bacterial diseases will not be limited to antibiotics in the future.…”