S.K. Otta

Detection of new hosts for white spot syndrome virus of shrimp using nested polymerase chain reaction

The presence of white spot syndrome virus (WSSV) of shrimp in various marine crustaceans was studied by using polymerase chain reaction (PCR). The incidence of the virus in non-cultured crustaceans from shrimp farms was also studied. The results indicate that wild-caught asymptomatic marine shrimp such as Metapenaeus dobsoni, Parapenaeopsis stylifera, Solenocera indica and Squilla mantis carry WSSV. This virus could be detected in apparently healthy marine crabs Charybdis annulata, C. cruciata, Macrophthalmus sulcatus, Gelasimus marionis nitidus and Metopograpsus messor. The virus could also be detected in asymptomatic Macrobrachium rosenbergii cultured inland far away from coast. Detection of carrier animals required two-step nested PCR.

Biofilm formation by Vibrio harveyi on surfaces

Abstract The role of biofilm in the survival and persistence of the bacterial shrimp pathogen Vibrio harveyi and its possible role in perpetuating infection in shrimp hatcheries was studied. Vibrio harveyi formed biofilms on all three substrates tested: cement slab, high density polyethylene (HDPE) plastic and steel coupons. Cell density was highest on the plastic surface followed by the cement slab and the steel surface. Biofilm on the three surfaces also exhibited differential sensitivity to the sanitiser chlorine, maximum resistance being found on the concrete slab followed by plastic and steel coupons. Planktonic cells were sensitive to short exposure to low levels of chlorine. Biofilm formation occurred even in the presence of the antibiotics chloramphenicol and tetracycline, both added to the medium at 50 ppm.

Histopathological and bacteriological study of white spot syndrome of Penaeus monodon along the west coast of India

Abstract White spot syndrome (WSS) is a serious viral disease of shrimp causing severe mortalities in several parts of Asia. This paper describes the histopathology of the syndrome which occurred on the west coast of India. The affected shrimp showed white spots on the carapace and post abdominal segments and histopathologically, hypertrophied nuclei with eosinophilic to basophilic intranuclear inclusion bodies were detected in the epithelial cells of the stomach. Moderate to heavy septicaemia was noticed in moribund shrimp.

Polymerase Chain Reaction in Detection of Gymnodinium mikimotoi and Alexandrium minutum in Field Samples from Southwest India

Abstract: Polymerase chain reaction (PCR) primers were constructed for the detection of two toxic dinoflagellate species, Gymnodinium mikimotoi and Alexandrium minutum. The primers amplified a product of expected size from cultured cells of G. mikimotoi and A. minutum. The species-specific primers targeting G. mikimotoi did not yield any product with a wide range of other cultured algae used as negative controls. Primers designed for A. minutum were species-group-specific since it PCR yielded a product from the closely related species A. ostenfeldii and A. andersonii, but not from other species of this genus tested. The confirmation of PCR products was performed by digestion of the products with restriction enzymes. Sensitivity analyses of the primers on DNA template from cultured cells was positive by PCR at a DNA template concentration of 1.5 × 10−4 ng/μl (0.3 cells/L) for A. minutum, and at a DNA concentration of 2.5 × 10−2 ng/μl (697 cells/L) for G. mikimotoi. The PCR method for detection of G. mikimotoi and A. minutum was applied on field samples collected with a plankton net. Gymnodinium mikimotoi could be detected in 11 field samples by microscopy, and all these field samples were positive by PCR. The cell counts of G. mikimotoi in simultaneously collected water samples ranged from 306 to 2077/L. Alexandrium minutum could be detected by microscopy in 3 different field samples. The cell counts in water samples collected at the same time as the net samples ranged from 115 to 1115 cells/L. Alexandrium minutum was detected by PCR in these field samples, with the exception of the sample displaying the lowest cell count (115 cells/L). Plankton samples that were negative by microscopy for any of the two target species were also negative by PCR. All the PCR products from field samples were confirmed by restriction enzyme digestion. The application of PCR-based detection of harmful algal bloom species for aquaculture and monitoring purposes in natural field samples is discussed.

Detection of monodon baculovirus and white spot syndrome virus in apparently healthy Penaeus monodon postlarvae from India by polymerase chain reaction

The simultaneous presence of monodon baculovirus (MBV) and whitespot syndrome virus (WSSV) in apparently healthy postlarvae of Penaeus monodon from different hatcheries in India was studied by nested polymerase chain reaction (PCR). MBV could be detected in 54% of the samples. However, only 15% of samples were positive by non-nested reaction. WSSV could be detected in 75% of samples, 19% being positive by non-nested reaction. The results show simultaneous presence of WSSV and MBV in many samples at various degrees of infection. Only 14% of the samples analysed were negative for both viruses. D 2003 Elsevier Science B.V. All rights reserved.