Investigating experimental pathogenicity of white spot syndromevirus in Litopenaeus vannamei with emphasis on the degree ofseverity (SOI)

Background and objective : Providing healthy food and required for increasing population and itsrole in the future of a healthy physical and mental development of human society ,and also newrequirements of propagation and breeding shrimp by using the latest technology ,new methodsfor researchers and experts and even authorities have opened . In this study pathogenicity ofvirus of white spot disease that is the cause of the death and destruction of shrimps, in theLitopenaeus vannamei have been studied experimentally.Materials and methods:In this research , ۲۰۰ Litopenaeus vannamei weighing approximately ۱۰-۱۲ gr were randomlyselected ,and Infected shrimps being tested , and by using diagnostic kits IQ۲۰۰۰ PCR have beenconfirmed . From the frozen body of Indian white shrimps that previously have shown symptomsof white spot disease, with using Nested Polymerase chain reaction (Nested-PCR) method, thevirus existence was proven, that was used as virus source, and during a day in several mealsalong with food was given to Litopenaeus vannamei. After ۳ days, clinical symptoms including:rapid separation of the cuticle from the epidermis, empty stomach and intestines, yellow andbrittle of hepatopancreas, and red moving limbs was observed. Samples of treatment grouptissues for histopathological studies fixed in Davidson's solution, and microscopic sectionsprepared and by hematoxylin - eosin stained, and white spot lesions in target tissues of virus,were studied comprehensively using light microscopy.Results:From the total samples , ۳۲ pieces showed clinical symptom of grade ۱ disease severity , and ۲۰pieces showed grade ۲ disease severity , and ۱۴ pieces showed grade ۳ disease severity , and ۵pieces showed grade ۴ disease severity . In Litopenaeus vannamei, there was grade ۱ and ۲ ofdisease severity. Rate of ROI was ۶۸/۸ %.

Keywords:

experimental pathogenicity , White spot syndrome virus , Litopenaeus vannamei , Pathology , ROI & SOI.