Streptococcus phocae, an emerging pathogen for salmonid culture

Abstract

This work describes the characterization of the causal agent of disease outbreaks that, from 1999, occurred repeatedly during the summer months (temperatures higher than 15 degrees C) in Atlantic salmon (Salmo salar) cage-farmed in Chile affecting both smolts and adult fish cultured in estuary and marine waters, reaching in some occasions a cumulative mortality up to 25% of the affected population. Diseased fish showed exophthalmia with accumulation of purulent and haemorrhagic fluid around eyes, and ventral petechial haemorrhages. At necropsy, haemorrhage in the abdominal fat, pericarditis, and enlarged liver, spleen and kidney are common pathological changes. Gram-stained smears revealed the presence of Gram-positive cocci, beta-hemolytic, negative for oxidase and catalase tests. Although biochemical characterization of the isolates using the miniaturized system rapid ID 32 Strep suggested their assignation to genus Gemella, sequencing and RFLP analysis of the 16S rRNA revealed that bacteria associated with the mortalities belong to Streptococcus phocae. Serological studies demonstrated that all the salmon isolates are antigenically homogeneous, which can facilitate the development of preventive measures and, although sharing some antigenical determinants, they belong to a different Lancefield group than the type strain isolated from seals. On the basis of these facts, we conclude that the species S. phocae is an emerging pathogen for salmonid culture in Chile, and it should be included as a new member of the warm water streptococcosis.

Comparative polyphasic characterization of Streptococcus phocae strains with different host origin and description of the subspecies Streptococcus phocae subsp. salmonis subsp. nov.

“…The morphological, physiological and biochemical characteristics useful in the identification of S. phocae have been detailed by several authors (Skaar et al, 1994;Gibello et al, 2005;Romalde et al, 2008). These phenotypic results indicated that S. phocae constitutes a homogeneous taxon with typical characteristics useful for the identification of this pathogen.…”

“…These phenotypic results indicated that S. phocae constitutes a homogeneous taxon with typical characteristics useful for the identification of this pathogen. However, serological studies demonstrated antigenic heterogeneity within this species, with the seal isolates classified into Lancefield's serogroups F and, in a much minor extent, C or untypable (Skaar et al, 1994;Vandamme et al, 1997), and the salmon isolates into serogroup G (Romalde et al, 2008).…”

“…The pathogen was further identified in other pinnipeds, including Cape fur seal (Arctocephalus pusillus pusillus) (Henton et al, 1999), ringed seal (Phoca hispida) (Raverty et al, 2004), grey seal (Halichoerus grypus) (Vossen et al, 2004), Caspian seal (Phoca caspica) (Kuiken et al, 2006), spotted seal (Phoca largha) (Hueffer et al, 2011), California sea lions (Zalophus californianus) (Johnson et al, 2006) and other marine mammals including southern sea otter (Enhydra lutris nereis) (Imai et al, 2009), in several countries of north-western Europe, North America, Africa and the Caspian Sea. Since 1999, S. phocae has also been isolated from diseased Atlantic salmon (Salmo salar) causing serious economic losses in the salmon industry in Chile during the summer months (Romalde et al, 2008).…”

Streptococcosis in farmed Litopenaeus vannamei: a new emerging bacterial disease of penaeid shrimp

“…Streptococcosis is an economically important disease that has been reported in over 30 farmed fresh and saltwater fish species including catfish (Shewmaker et al 2007), tilapia (Eldar et al 1995), trout (Hoshina et al 1958, Eldar et al 1995, salmon (Romalde et al 2008), red drum (Eldar et al 1999), flounder (Baeck et al 2006), yellowtail (Kusuda et al 1991), hybrid striped bass (Evans et al 2000) and turbot (Toranzo et al 1994). The occurrence of streptococcosis in fish appears to be stress related with low grade chronic mortalities seen in some fish species and acute mortalities of 30 to 50% occurring in others as a result of an encephalitis and/or systemic infection affecting multiple organs (Eldar et al 1995, Ringo & Gattesoup 1998, Camus et al 2008).…”

Efficacy of a commercial disinfectant against Vibrio ordalii, Vibrio anguillarum, Francisella sp. and Infectious Pancreatic Necrosis Virus (IPNV) pathogens of Atlantic salmon (Salmo salar) farmed in Chile

“…Besides its disinfecting inTRODuCTiOn Fish diseases of major importance in Chilean salmon farming includes infectious pancreatic necrosis (iPn) and Piscirickettsia salmonis (Fryer and Hedrick 2003), which cause significant economic losses due to mortalities of atlantic salmon, Salmo salar, fry and post-smolt in seawater. in addition, an increase in disease detection of emergent pathogens as Vibrio ordalii (Colquhoum et al 2004), Streptococcus phocae (Gibello et al 2005, Romalde et al 2008, Francisella (Birkbeck et al 2007) and, lately, Vibrio anguillarum (avendaño-Herrera et al 2007) has been observed in the last decade. To date, economic losses caused by these bacterial pathogens, except V. ordalii, have decreased; however, it remains one of the properties, few studies have been designed to assess the quaternary ammonium compounds, particularly a synergistic blend of superquats and glutaraldehyde (Duplalim ® , Veterquímica S.a., Chile), which is commercialized as a disinfectant of broad spectrum, presenting fast action and low toxicity.…”