A fragment sized 400bp of White spot syndrome virus(WSSV,formerly designated NOSV),recovered from recombinant plasmid pAFD, was labeled with Digoxigenin as a probe to detect dynamic distribution of WSSV within 120h and 72h in crawfishes( Cambarus proclarkii ) inoculated WSSV by oral taking and injection respectively. Stomach epithelium, intestine epithelium, heart, gill, haemolymph, muscle, hepatopancreas, hypoderm, connective tissue and ovary of infected crawfishes were examined for WSSV. In both groups, WSSV was first detected in heamolymph at 12h p.i. and then disappeared. Again it was detected at 96h p.i. only in oral infection group and maintained till 120h p.i., but it didn’t appear at 72h p.i. in injection group. WSSV in heart, muscle was detected at 36h p.i. in oral infection group and 24h p.i. in injection group respectively, and then increased generally. In addition, WSSV in intestine epithelium, connective tissue, ovary of oral infection group and intestine epithelium, hypoderm, ovary of injection group could also be detected. In dead crawfishes after 120h and 72h p.i. in two groups, WSSV could be detected in all the examined tissues and it demonstrated that systemic infection occurred in the animales. The tissue containing more amounts of WSSV was hypoderm in oral infection group, while intestine epithelium, gill, hypoderm, ovary in injection infection group. It deduced that WSSV first appears in haemolymph and then goes into heart, muscle and other tissues and proliferates in them. Once again, WSSV is released into heamolymph resulting in systemic infection till crawfishes’ death.
