CONCENTRATING WHITE SPOT SYNDROME VIRUS BY SKIM MILK FLOCCULATION FOR DETECTION BY A MONOCLONAL ANTIBODY BASED FLOW-THROUGH ASSAY

Camerson Donald Ghambi ^a,b, Kalkulisha Shankar ^a, Prakash Patil ^a, Satish Rama Poojary ^a, Abhiman Ballyaya^a Ramesh Srinivasayya ^a
^aAquatic Animal Health Management Laboratory, Department of Aquaculture, College of Fisheries, Karnataka Veterinary Animal and Fisheries Science University, Mangalore 575 002, India
^bDepartment of Aquaculture, Lilongwe University of Agriculture and Natural Resources, P.O. Box 219, Lilongwe, Malawi

Since its emergence, white spot syndrome virus has caused huge loss to shrimp aquaculture. Although early detection of viruses in water is a prerequisite to evade epizootics but the greatest obstacle is that they are present in very low copy number and hence, concentrating them is very much essential. To address this, the present study was conducted in seawater under acidic (pH 3.5) and neutral (pH 7.4) conditions to concentrate WSSV by a one-step concentration method using skim milk (0.01%) as an organic flocculent and detection by a MAb based flow-through assay, RapiDot. This method under in-vitro conditions was developed and standardized to concentrate WSSV VP28 which was detectable by RapiDot in both subsurface and floc samples. WSSV concentrated from seawater in 2 L, 1 L and 50 mL from the shrimp infection experiment was tested where RapiDot detected WSSV earlier compared to 1-step PCR in floc samples and overall acidified seawater in 2 L gave the best results. However, concentrating WSSV in seawater under normal pH which is simple than acidified environment equally performed well and is recommended for field level.

A 36 h duration study was conducted in seawater under acidic (pH 3.5) and normal (pH 7.4) conditions to concentrate WSSV by a one-step concentration method using skim milk (0.01%) as an organic flocculent and detected by a MAb based flow-through assay, RapiDot. This method was developed and standardized under in-vitro conditions to concentrate WSSV VP28 for detection by RapiDot and PCR in both subsurface and floc samples. WSSV concentrated from seawater in 2 L, 1 L and 50 mL from the shrimp infection experiment was tested by RapiDot and PCR.

WSSV VP28 was detectable by RapiDot in both subsurface and floc samples. WSSV concentrated from seawater from the shrimp infection experiment was detected earlier by RapiDot compared to 1-step PCR in floc samples and overall acidified seawater in 2 L container was the best. However, concentrating WSSV in seawater under normal pH which is simple than acidified environment equally performed well and is recommended for field level.