Mass mortality of giant abalone Haliotis gigantea caused by a Francisella sp. bacterium

Abstract

In February 2005, a mass mortality of giant abalone Haliotis (Nordotis) gigantea Gmelin, 1791 occurred on a private abalone farm in Shimane Prefecture, Japan. The cumulative mortality rate reached about 84%. In histological observations, bacteria-like spherical particles were found in affected animals, suggesting a bacterial infection. Many of the bacteria-like particles were found in the cells that were presumably host phagocytes. DNA was extracted from the hemolymph of a diseased abalone and a bacterial 16S rRNA gene was amplified by PCR. The bacterium was classified within the genus Francisella by gene sequence analysis. A bacterial isolate was obtained by spreading hemolymph of a diseased abalone on modified Eugon agar dissolved in 70% seawater containing 1% (w/v) hemoglobin. A gene fragment of the expected size was amplified from the bacterial isolate by PCR using specific primers for the 16S rRNA gene obtained from the diseased abalone. Experimental infections were carried out by intramuscular injection with the bacterial isolate or by immersion in the bacterial suspension using 2 species of abalone, the giant abalone and the Japanese black abalone Haliotis (Nordotis) discus discus Reeve, 1846. Most (98.6%) of the abalone challenged with the bacterial isolate died in experimental infections. These results suggest that the Francisella sp. isolate was the causative agent for the mass mortality of giant abalone. This is the first report of a pathogenic Francisella sp. isolate for mollusks.

Disease and mortality among Yesso scallops Patinopecten yessoensis putatively caused by infection with Francisella halioticida

“…These discrepancies could be attributed to comparison of bacteria from chronic in situ infections (this study) versus cultured bacteria which were in active growth phase (Brevik et al 2011). In addition, The strong positive ISH reaction to the bacteria under investigation in this study concurs with those for F. halioticida (Kamaishi et al 2010). However, an equally strong positive ISH reaction was coincidently observed with Rickettsia-like prokaryotes in the gill epithelium of the 'healthy' population of scallops.…”

“…The hybridization solution and probe concentration of each of the 3 probes used in combination was the same as published by Kamaishi et al (2010); however, the incubation time was shortened to 2 h at 60°C (overnight incubation at 39°C was eliminated). The post hybridization washes were the same as published, and similarly, the signal was detected immunologically using anti-digoxigenin-alkaline phosphate Fab fragments (Roche) in conjunction with BCIP/NBT liquid substrate system (Sigma-Aldrich) and counterstained using Bismark Brown Y.…”

“…The 3 oligonucleotide probes Megai-110r, Megai-230r and Megai-870r (Kamaishi et al 2010) were purchased with the 3' end digoxigenin label already incorporated (Integrated DNA Technologies). Proteinase K concentration was increased to 10 µg ml −1…”

“…Five µm tissue sections were deparaffinized, and in situ hybridization (ISH) was performed based upon the procedures and probes published by Kamaishi et al (2010), with minor modifications as follows. The 3 oligonucleotide probes Megai-110r, Megai-230r and Megai-870r (Kamaishi et al 2010) were purchased with the 3' end digoxigenin label already incorporated (Integrated DNA Technologies).…”

“…For example, F. tularensis causes a highly contagious and serious disease of mammals (Oyston 2008) and F. noatuensis can cause a severe systemic granulomatous inflammatory disease in fish (Nylund et al 2006, Jones & Smith 2014. Similarly, F. halioticida is also known to be pathogenic and was originally described as the cause of mass mortality among farmed abalone Haliotis gigantea in Japan (Kamaishi et al 2010, Brevik et al 2011.…”