MLBA 9:  June / July 2009

 

 

 

 

Aquaculture is the fastest grow­ing food sector globally and has established itself as a high protein resource to fulfil the food de­mand since the natural resources ex­hibits over-exploitation.

 

But the biggest problem faced by the aquaculture industry worldwide is diseases caused due to various bio­logical and non-biological agents. Among the groups of microorganisms that cause serious losses in shrimp culture, the best known are bacteria because of the devastating economic effects they have on affected farms.

 

Bacterial diseases, mainly due to Vibrio, have been reported in penaeid shrimp culture systems implicating at least 14 species and they are Vibrio harveyi, V. splendidus, V. parahaemo­lyticus, V. alginolyticus, V. anguil­larum, V. vulnificus, V. campbelli, V. fischeri, V. damsella, V. pelagicus, V. orientalis, V. ordalii, V. mediterrani, V. logei etc.

 

Vibriosis is a bacterial disease responsible for mortality of cultured shrimp worldwide (Lightner & Lewis, 1975; Adams, 1991; Lightner et al., 1992; Lavilla-Pitogo et al., 1996; Lavilla-Pitogo et al., 1998; Chen et al., 2000).

 

Vibrio species are widely distrib­uted in culture facilities throughout the world. Vibrio-related infections frequently occur in hatcheries, but epizootics also commonly occur in pond-reared shrimp species. Vibriosis is caused by gram-negative bacteria in the family Vibrionaceae.

 

Outbreaks may occur when en­vironmental factors trigger the rapid multiplication of bacteria already tolerated at low levels within shrimp blood (Sizemore & Davis, 1985), or by bacterial penetration of host bar­riers. The exoskeleton provides an effective physical barrier to patho­gens trying to penetrate the external surface of crustaceans, as well as the foregut and hindgut.

 

However, Vibrio spp. is among the chitinoclastic bacteria associated with shell disease (Cook & Lofton 1973) and may enter through wounds in the exoskeleton or pores (Jiravanichpais­al & Miyazaki, 1994; Alday-Sanz et al,. 2002).