Abstract:
White spot syndrome is a viral infection of Penaeid shrimp. The
disease is highly lethal, contagious and killing shrimps quickly. Since this
disease is caused by a virus, there is no anti-viral treatment for the disease.
Sri Lanka is a country involving in large scale intensive shrimp farming. Most
of shrimp products are export oriented. WSSV cause severe damage to
shrimps and prawns while leading to economic lost. DNA extraction kits are
available in the country to find out the positive samples for white spot
disease. But these kits are expensive. Therefore this study aimed to optimize
a molecular detection kit totally made locally for detecting WSSV in shrimps
for a lower cost. A viral DNA extraction kit and single-tube, non-stop, semi nested polymerase chain reaction (PCR) technique was developed for
simultaneous detection and severity grading of white spot syndrome virus
(WSSV) infections in the black tiger shrimp. The test uses 1 sense primer
and 3 antisense primers that produce up to 3 PCR products (1100, 526 and
250 base pairs) depending upon the severity of infection. Specifically, heavy
infections (≥2×104 viral particles) of WSSV produce all 3 fragments, while
moderate infections (around 2×103 viral particles) produce 2 (526 and 250
bp) and light infections (20 to 200 viral particles) produce 1 (250bp). The
non-stop, single-tube, semi-nested PCR technique is simple and convenient
and can detect as little as 5fg WSSV DNA (20 viral particles) in crude
extracts of post larval samples or extracts of gills, tail and pleopods from
larger shrimp.
