Lactococcus garvieae: an emerging bacterial pathogen of fish

Abstract

Lactococcus garvieae is the causative agent of lactococcosis, a hyperacute, haemorrhagic septicaemia of fish. This bacterium is also considered an emerging zoonotic pathogen, as reports of human infection are increasing. Significant economic loss in aquaculture is suffered as a result of lactococcosis, as numerous freshwater and marine species of commercial interest are affected. Development of antibiotic resistance in L. garvieae to several chemotherapeutic agents complicates and restricts treatment options. Effective, sustainable treatment and prevention options are thus needed, but progress is impeded by the lack of knowledge concerning several aspects of the disease and the pathogen. This review aims to present the latest research on L. garvieae, with specific focus on pathogenesis, virulence factors, risks associated with chemotherapeutic administration and possible control options.

Bacteria-Affecting Cephalopods

“…This is a gram-positive bacterium, which causes diseases in several aquatic and terrestrial animals (Tsai et al 2012). In fish, it is responsible for hyperacute haemorrhagic septicaemia, but it has also been identified in bacterial outbreaks in aquatic invertebrates, such as the giant freshwater prawn, Macrobrchium rosenbergii (Vendrell et al 2006;Tsai et al 2012;Meyburgh et al 2017). This bacterium has been reported in several species of fish, but it has also detected in other marine animals, such as a bottlenose dolphin, Tursiops truncatus (Evans et al 2006) and a sea turtle, Caretta caretta (Fichi et al 2016).…”

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“…Indiscriminate use of antibiotics causes microorganisms to develop antibiotic resistance mechanisms, a potential threat to the environment, as well to aquaculture, and to public health (Vendrell et al, 2006;Austin & Austin, 2012;Altun, Onuk, Ciftci, Büyükekiz, & Duman, 2013;Meyburgh, Bragg, Boucher, 2017). The acquisition of antibacterial resistance in L. garvieae was shown by screening for antibiotic resistance genes (Raissy & Moumeni, 2016;Türe & Alp, 2016).…”

Lactococcosis in Reared Fish in Brazil and Control Strategies

“…Antibiotic therapy is not an effective control measure for L. garvieae infection [13,20], and losses can exceed 80% of total production [3]. Application of chemotherapeutic agents is effective under experimental conditions, but is ultimately an unsustainable strategy in the control of lactococcosis due to the development and spread of antibiotic resistance [21].…”

“…Nowadays, vaccination is considered the best option to control lactococcosis, due to the poor efficiency of chemo-therapeutic agents under field conditions and the risks associated with the spread of antibiotic resistance [21]. The alternatives investigated in the control of lactococcosis have been intraperitoneal injection of L. garvieae bacteriophages in farmed fish [29], utilization of Aeromonas as a probiotic to stimulate innate immunity, increasing the number of leukocytes, improving phagocytic activity and the respiratory activity of leukocytes [30], and the most effective alternative, that is vaccination with formalin inactivated L. garvieae strains [3].…”