Virulence of Vibrios Isolated from Diseased Black Tiger Shrimp, Penaeus monodon, Fabricius

Abstract

Vibrios are prominently opportunistic, but they may act as primary and secondary pathogenic invaders of shrimps in farms worldwide. However, little is known about the virulence of diverse vibrios harbored in shrimp farms. The isolation of secondary/opportunistic Vibrio pathogens was carried out from the shrimp farms located in peninsular India, reported to have mass mortalities because of White‐spot syndrome virus and shell disease outbreaks. The isolates were identified and grouped into six species including luminescent Vibrio harveyi, Vibrio alginolyticus, Vibrio vulnificus, Vibrio fischeri, Vibrio parahaemolyticus, and Photobacterium damsela. To make a detailed study on their virulence, the isolates were screened in vitro for the production of extracellular factors. In the present study, 68.9% of the shrimp Vibrio isolates were found to be positive for both phospholipase and hemolysin production. The results showed that various factors including hydrophobicity, presence of capsule, and production of extracellular enzymes such as lipase, protease, phospholipase, and hemolysin were responsible for pathogenesis. Using the bacterial adherence to hydrocarbons, most of the strains were classified as highly hydrophobic. In vivo challenge experiments using the Vibrio species and the extracellular products demonstrated the pathogenicity of vibrios. In the present study, we established the shrimp farm water isolates V. vulnificus, V. fischeri, and P. damsela as moderately opportunistic shrimp pathogens.

Efficacy of marine green alga Ulva fasciata extract on the management of shrimp bacterial diseases

“…Shrimps were intramuscularly injected with 0.1 mL of bacterial inoculums using a 1 mL tuberculin syringe at ventral side between the second and third segment. Preliminary examinations revealed that challenge dose of 10 3 colony forming unit (cfu) per shrimp could not kill the injected shrimp (Manilal et al, 2010b). Therefore the concentrations of 10 5 to 10 8 cfu of the appropriate single (V. fischeri, V. alginolyticus, V. harveyi and Aeromonas sp.)…”

“…Ten shrimps were used for each inoculation level. The mortality and reflexes of the shrimps were observed for every 15 min in the first hour of post-inoculation and every 1 h until the 6 th h (Manilal et al, 2010b). Subsequent monitoring was done every 12 h for a period of seven days (Tendencia & Dureza, 1997).…”

“…Subsequent monitoring was done every 12 h for a period of seven days (Tendencia & Dureza, 1997). The appropriate concentration of pathogens (10 5 to 10 8 cfu), which causes mortality within 24 h or within 7 days, was considered as LD 50 whereas which causes infection or abnormalities was considered as ID 50 (Infectivity Dose) (Manilal et al, 2010b). The LD 50 dose was calculated by the probit method, after Wardlaw (1985).…”

“…Bacterial disease outbreaks particularly vibriosis and black shell disease impose a significant constraint on the sustainable production of shrimp (Bachere et al, 1995;Verschuere et al, 2000;Selvin et al, 2005;Manilal et al, 2010b). In Asia, among the pathogenic Vibrio group, 11 species were reported from the shrimp culture systems (Lavilla-Pitogo, 1995).…”

“…In Asia, among the pathogenic Vibrio group, 11 species were reported from the shrimp culture systems (Lavilla-Pitogo, 1995). V. alginolyticus and V. harveyi poses a serious disease problem in cultured black tiger shrimp in India (Karunasagar et al, 1997;Selvin & Lipton 2003a;Manilal et al, 2010b). Vibrio species are considered to be members of the normal bacterial flora of shrimp and the culture environment (Jiravanichpaisal et al, 1994;Otta et al, 1999).…”