Immunological findings in shrimp Litopenaeus vannamei exposed to attenuated WSSV vaccine produced by Gamma irradiation

In this research, White spot syndrome virus (WSSV) with ۱۰۵.۴LD۵۰.mL-۱ inactivated with gamma irradiation at a dose rate of ۱۴-۱۵ kGy.sec-۱ was used as a vaccine. Three hundred and sixty shrimp of Litopenaeus vannamei, medium body weight (MBW) ۱.۰±۰.۱۷g), were prepared and experimentally exposed. They were distributed among four groups, inclusing vaccinated-virus exposed (T۱), vaccinated-nonvirus exposed (T۲), virus exposed (Positive control as T۳) and non-vaccinated-non-virus exposed (Negative control as T۴). The mortality percent of T۱ started from day ۵ and reached the highest (۵۰%) on day ۱۱ and remained constant until end of the experiment. In T۲, no mortality was observed until the ۳rd day and the maximum mortality (۲۰%) was observed on day ۹. On the other hand, no remarkable mortality was recorded for T۴ unlike T۳ in which the mortality started on day ۲ and stopped on day ۷. The minimum density of hyalinocyte was calculated in T۴ but the maximum one was found in T۳ (۱۷.۷۷±۰.۳۳) with no significant differences (p<۰.۰۵) compared to T۲ (۱۶.۵۹±۰.۹۶). A significant difference (p<۰.۰۵) was observed between the values of Total Haemocyte Count (THC) before and after exposing to virus in T۱. Total Protein Plasma (TPP) decreased to ۲۹.۰۳±۳.۴۱, while it was higher than ۲۵.۹۶±۲.۷۵ in T۳ after ۷ days. Such results might be responsible for developing resistance against WSSV in gamma irradiant vaccine in L. vannamei in comparison to T۳ while the cause of mortality in T۲ could be due to the lower effectiveness.

Keywords:

WSSV , Gamma irradiant , Haemolymph parameters , Mortality rate