Outbreaks of Edwardsiella ictaluri Infection in Ayu Plecoglossus altivelis in Japanese Rivers

Abstract

ABSTRACT-From middle August to early October in 2007, mortalities in wild ayuPlecoglossus altivelis occurred in the rivers of Tokyo Metropolis, Yamaguchi Prefecture and Hiroshima Prefecture, Japan. Hemorrhagic ascites was observed in almost all the examined fish. Some fish showed reddening of body surface, anus or bases of fins and exophthalmos. A single species of bacteria was isolated from the kidney, spleen and ascites of all the examined fish and identified as Edwardsiella ictaluri. Pathogenicity against ayu of the bacterial isolates was demonstrated by experimental infections, with the LD 50 being approximately 10 4 CFU/fish. The dead fish exhibited similar disease signs to those of naturally affected fish. From these results, it was concluded that the present mortality of wild ayu was caused by E. ictaluri infection. This is the first report on E. ictaluri infection of fish in Japan.

Characterization of Edwardsiella ictaluri Isolated from Wild Ayu Plecoglossus altivelis in Japan

“…These were isolated from the kidney of diseased ayu, which were caught in rivers in Tokyo Metropolis, Yamaguchi Prefecture and Hiroshima Prefecture from August to October 2007 (Sakai et al, 2008). Bacteria were cultured on Trypto-Soya agar (TSA; Nissui, Japan), and stored in heart infusion broth (HIB; Eiken, Japan) containing 10% glycerol at -80°C until used.…”

“…In 2007, a Gram-negative bacterium was isolated from diseased wild ayu Plecoglossus altivelis, which were caught in rivers of three locations, Tokyo Metropolis, Yamaguchi Prefecture and Hiroshima Prefecture, Japan (Sakai et al, 2008), and the disease was diagnosed as E. ictaluri infection. This paper describes the detailed phenotypic and genetic characteristics of the E. ictaluri strains isolated from diseased wild ayu.…”

Kajian patogenisitas bakteri Edwardsiella ictaluri pada ikan patin Pangasionodon hypophthalmus

“…Penyakit ini awalnya diketahui hanya menginfeksi ikan Channel catfish Ictalurus punctatus, namun kemudian dapat menginfeksi jenis catfish lainnya seperti ikan lele, patin, dan sidat. Spesies selain catfish yang dilaporkan dapat terinfeksi E. ictaluri yaitu ikan nila Oreochromis niloticus (Soto et al, 2012) dan ikan ayu Plecoglossus altivelis Sakai et al, 2008). Secara eksperimental ikan white perch Morone americana, chinook salmon Oncorhynchus tshawytscha, dan rainbow trout O. mykiss (Pasnik et al, 2007) serta zebrafish Danio rerio (Petrie-Hanson et al, 2007) juga dapat terinfeksi oleh bakteri ini.…”

“…Hasil penelitian menunjukan setelah ikan patin diinfeksi secara intraperitoneal dengan konsentrasi E. ictaluri berbeda, dari konsentrasi 10 4 cfu/mL sampai dengan 10 10 cfu/mL menimbulkan gejala klinis antara lain: timbulnya bercak merah pada kulit, pembengkakan abdomen, dan ikan berenang dengan kepala di permukaan air/vertikal, namun ikan patin uji yang diinfeksi dengan konsentrasi bakteri 10 Sakai et al (2008) menyatakan bahwa beberapa tanda klinis pada penyakit ESC adalah adanya bercak merah pada kulit dibawah rahang, operkulum, disekitar perut, dan anus serta bagian bawah sirip. Terjadinya pembengkakan abdomen dan organ dalam seperti hati, ginjal, dan limpa serta sebelum mati ikan berenang menggantung hampir vertikal dengan kepala di permukaan air (Kim & Park, 2015).…”

“…Perhitungan LD50 menunjukkan bahwa kepadatan E. ictaluri yang menyebabkan kematian 50% (LD50) ikan patin yaitu 2,8×10 4 cfu/mL. Seperti yang disebutkan Sakai et al (2008) oleh Dong et al (2015), infeksi E. ictaluri dengan konsentrasi 2,6×10 6 sel/mL menyebabkan kematian sampai 80% pada ikan patin P. hypophthalmus. Hal ini membuktikan bahwa E. ictaluri bersifat sangat patogen terhadap ikan patin karena infeksi kepadatan yang rendah telah menyebabkan tingginya mortalitas dan ikan patin P. hypophthalmus merupakan salah satu inang definitif bagi bakteri E. ictaluri.…”