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Mortality among farmed mud crab, Scylla serrata due to white spot syndrome virus (WSSV) in Andhra Pradesh, India

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Title Mortality among farmed mud crab, Scylla serrata due to white spot syndrome virus (WSSV) in Andhra Pradesh, India
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Creator R. Ananda Raja
KP. Jithendran
Rajan J.J.S
Madhanagopal R
M. Poornima
S.V. Alavandi
KK.Vijayan
 
Subject Crab Mortality
Mud crab, Scylla serrata
White spot syndrome virus (WSSV)
Barnacle
 
Description Not Available
Mud crab, Scylla serrata farming had been initiated in the abandoned vannamei ponds in Andhra Pradesh, India since 2016. Total area under mud crab culture in Andhra Pradesh was 7363.81 hectares during 2017-18. The crab farming in earthen ponds was done using the green local (GL) crabs (100-200g) from export portals (Odisha, Tamil Nadu, Puducherry, Kerala, Karnataka, Maharashtra and Goa) with the stocking density of 0.1 per sq. mt. Crab mass mortality was observed in Nagayalanka, Krishna district with clinical signs such as white spots on the carapace, lethargy, fungal growth over the skeleton, chitinolytic spot on the abdominal flap, fouling, broken claw, loss of chelate legs, and light greenish to yellowish or pinkish discoloration followed by death. Mortality was observed during 65th day of culture (DOC) and progressed up to 75% in a period of 10 days. Hence, emergency harvest was done on 75th DOC. Water and pond sediment samples were collected from diseased and healthy farms (four farms with 21 ponds). Water salinity, pH, dissolved oxygen and temperature were 16.67±0.18 ppt, 8.16±0.01, 3.75±0.06% and 26.68±0.06oC, respectively. Moribund and healthy crabs were collected with an average size of 781.25±33.56g. On spot post-mortem examination was done and the samples were collected in suitable preservatives. Post mortem examination revealed that the gills were heavily infested (left gill-74.8±11.81; right gill-72.3±11.95) with metazoan crustacean parasite, stalked barnacle, Octolasmis spp. Abdominal cavity contained about 30-40mL serosanguinous fluid. Microbial load estimation in pond sediment, water and haemolymph of infected pond were significantly higher than that of healthy ponds. Haematological investigation revealed that the healthy mud crab had higher total haemocyte count (THC) of 17.28±0.46 x 106 cells mL-1 while the diseased crabs had THC of 6.90±0.48 x 106 cells mL-1. The differential haemocyte population was characterized based on the presence of the cytoplasmic granules and cell sizes. Small non-granular (SNGH) and large non-granular (LNGH) haemocytes populations were found significantly increased while semi-granular or small-granular (SGH) and large granular (LGH) haemocytes were drastically reduced in diseased crabs compared to that of healthy crabs. Polymerase chain reaction (PCR) screening for white spot syndrome virus (WSSV) revealed that the diseased samples were positive. Histopathology showed that there was degeneration of gill tissue and were characterized by hypertrophied nuclei with marginated chromatin and eosinophilic to basophilic intranuclear inclusions. It is advisable to stock disease free crablets and follow strict better management practices to avoid disease outbreaks in future.
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Date 2020-03-09T10:21:27Z
2020-03-09T10:21:27Z
2019-08-21
 
Type Book
 
Identifier Ananda Raja, R., Jithendran, K.P., Rajan, J.J.S., Madhanagopal, R., Poornima, M., Alavandi, S.V and Vijayan, K.K. 2019. Mortality among farmed mud crab, Scylla serrata due to white spot syndrome virus (WSSV) in Andhra Pradesh, India. Presented in the “International conference on current immunological tools for biodiversity and status of environment health” organized by the Centre of Advanced Study in Marine Biology at Parangipettai, India during 21 to 23rd August, 2019. p 16-17. ISBN No. 978-3-659-29407-5.
978-3-659-29407-5
http://krishi.icar.gov.in/jspui/handle/123456789/33703
 
Language English
 
Relation Not Available;
 
Publisher Not Available