Pathogenicity profile of Vibrio parahaemolyticus in farmed Pacific white shrimp, Penaeus vannamei
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Date
2017
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Abstract
A pathobiological study was conducted using Vibrio parahaemolyticus (VP) strain isolated from vibriosis
affected shrimp (Penaeus vannamei) farms in Kancheepuram and Thiruvallur districts of Tamil Nadu
during August 2014 to February 2015. The isolate was identified based on the morphological, physiological,
biochemical and molecular characters. LD50 value with intramuscular injection was determined
as 2.6 104 cfu/shrimp and sequential pathology was studied giving 6.1 103 cfu/shrimp (LD25). Total
plate count (TPC) and total Vibrio count (TVC) in water, pond sediment, haemolymph, muscle, HP and gut
were found significantly (P < 0.01) higher in natural cases than the experimental set up. Clinical signs
and lesions observed in the natural and experimental cases were anorexia, lethargy, cuticle softening,
loose shells, abdominal muscle cramp, red discoloration, opaque and whitish abdominal and tail
musculature, necrosis of exoskeleton or splinter burns, reddish pleural borders of antennae, uropods and
telson, swollen tail fan, ulcers, moribund shrimp sinking to bottom, and mortalities with shrunken
discoloured HP with empty gut. Total haemocyte count (THC), small nongranular haemocyte (SNGH),
large nongranular haemocyte (LNGH), small granular haemocyte (SGH) and large granular haemocyte
(LGH) counts lowered significantly (P < 0.01) at 3, 6, 12, 24, 48, 96 and 192 h post injection (p.i). No LGH
were found after 96 h of challenge. The post injection qPCR analyses of haemocytes showed upregulations of penaeidin-3a, lysozyme, prophenoloxidase I, prophenoloxidase II and serine protein at 3 and 6 h of infection. There was total down-regulation of crustin from 3 to 192 h p.i. There was a remarkable elevation in the level of proPO I with concomitant depletion of proPO II. The pattern of upand down-regulations in proPO I and SP were similar.
Description
TNV_FSI_2017_67(368-381)
Keywords
Veterinary Science