A Nonluminescent and Highly Virulent Vibrio harveyi Strain Is Associated with “Bacterial White Tail Disease” of Litopenaeus vannamei Shrimp

Abstract

Recurrent outbreaks of a disease in pond-cultured juvenile and subadult Litopenaeus vannamei shrimp in several districts in China remain an important problem in recent years. The disease was characterized by “white tail” and generally accompanied by mass mortalities. Based on data from the microscopical analyses, PCR detection and 16S rRNA sequencing, a new Vibrio harveyi strain (designated as strain HLB0905) was identified as the etiologic pathogen. The bacterial isolation and challenge tests demonstrated that the HLB0905 strain was nonluminescent but highly virulent. It could cause mass mortality in affected shrimp during a short time period with a low dose of infection. Meanwhile, the histopathological and electron microscopical analysis both showed that the HLB0905 strain could cause severe fiber cell damages and striated muscle necrosis by accumulating in the tail muscle of L. vannamei shrimp, which led the affected shrimp to exhibit white or opaque lesions in the tail. The typical sign was closely similar to that caused by infectious myonecrosis (IMN), white tail disease (WTD) or penaeid white tail disease (PWTD). To differentiate from such diseases as with a sign of “white tail” but of non-bacterial origin, the present disease was named as “bacterial white tail disease (BWTD)”. Present study revealed that, just like IMN and WTD, BWTD could also cause mass mortalities in pond-cultured shrimp. These results suggested that some bacterial strains are changing themselves from secondary to primary pathogens by enhancing their virulence in current shrimp aquaculture system.

Identification and characterisation of an ostreid herpesvirus-1 microvariant (OsHV-1 µ-var) in Crassostrea gigas (Pacific oysters) in Australia

“…Elevated temperatures have also been associated with increased populations of pathogenic Vibrio spp. (Motes et al 1998, Zimmerman et al 2007, Pernet et al 2012, Zhou et al 2012, which is consistent with findings from this study demonstrating an increased incidence of V. harveyi in oysters collected from Quibray Bay when the water temperature was 22 to 23°C, compared to oysters collected in early November when the water was at 18°C.…”

Advances, challenges, and directions in shrimp disease control: the guidelines from an ecological perspective

“…Extensive studies have isolated bacterial pathogens in aquaculture systems, especially Vibrio species, and then evidenced by challenge tests (Soto-Rodriguez et al 2015;Zhou et al 2012). However, Vibrio species have been frequently isolated from the intestines of healthy shrimp as well as surrounding water samples (Zheng et al 2016).…”

“…Conversely, under environmental stress, such as significantly increased COD, NO 2 − , and PO 4 3− concentrations in ponds with diseased shrimp, the composition of the ambient microbiota is disrupted and results in an enrichment of potential pathogens and decreased probiotic species (Xiong et al 2014b). In addition, environmental pressure can enhance pathogen virulence (Verschuere et al 2000;Zhou et al 2012) and increase the susceptibility of shrimp to infection (Beardsley et al 2011;Tseng and Chen 2004). As a result, these additive effects cause increased infectivity and the emergences of shrimp disease (Fig.…”

“…A possible explanation is that shrimp are more sensitive to infection under stressful conditions (Hsu and Chen 2007). Alternatively, opportunistic pathogens can convert from non-virulent to virulent or exhibit enhanced virulence under changing conditions (Munro et al 2003;Zhou et al 2012). Continuous monitoring of biogeochemical parameters has provided a basis for strategies to improve the rearing conditions and to avoid environmental collapses (Ferreira et al 2011).…”

Identification of highly expressed host microRNAs that respond to white spot syndrome virus infection in the Pacific white shrimp Litopenaeus vannamei (Penaeidae)

“…Pacific white shrimp (Litopenaeus vannamei) is the most widely cultured crustacean species in the world due to its high yield and low-demand for concentration of salt (Zhou et al, 2012). Over the last three decades, viral pathogens, in particular white spot syndrome virus (WSSV), have seriously threatened the shrimp aquaculture industry and caused severe economic losses (Naylor et al, 2000).…”