Transmission of white spot syndrome virus (WSSV) in shrimp has been reported to occur
by feeding and immersion. In the present study, the impact of the molt process and
artificial lesions in the cuticle on shrimp susceptibility to WSSV was examined using
intramuscular and immersion routes.
For the intramuscular route, Penaeus (Litopenaeus) vannamei shrimp (n = 450) were
injected with 102.3 up to 102.7 shrimp infectious dose 50% end point (SID50) of WSSV in
early and late post-molt, inter-molt, early and late pre-molt; resp. A-, B-, C-, D1- and D2-
stage. The resulting infection titers demonstrated that no difference (p > 0.05) in
susceptibility existed between different molt stages when virus was injected.
For the waterborne route, shrimp in different molt stages were immersed in seawater
containing 104 SID50 ml1 of WSSV. In a first study, P. vannamei (n = 125) incubated in cell
culture flasks, became infected with WSSV mostly in post-molt stages. In a second study, 2
groups of P. vannamei (n = 100) and P.monodon (n = 100) were transferred into plastic bags
to prevent damage to the cuticle; and in 1 group a pleopod was cut off prior to incubation.
Induction of damage increased infection significantly (p < 0.05) in A-stage from 0–40% to
60–100%, in B-stage from 0–20% to 40–60%, in C-stage from 0–20 to 20–60%, while
infection was 0% in D-stages with both immersion methods.
This study proved that shrimp are more susceptible to WSSV infection via immersion
after molting than in the period before molting and wounding facilitates infection.
2009 Elsevier B.V. All rights reserved.