First report of pedunculate barnacle (Octolasmis neptuni), as potential asymptomatic carrier of white spot syndrome virus (WSSV)

White spot syndrome virus (WSSV) is a notorious virus infecting cultured shrimps affecting the aquaculture industry for more than two decades over the world. WSSV has been isolated from asymptomatic carriers including crabs, artemia, rotifers, polychaetes and insects. Asymptomatic carriers are hosts that do not exhibit infection symptoms but carries infection to other hosts. The potential virulence of asymptomatic carrier of WSSV in multiple hosts were screened in the current study. The symbiotic Octolasmis neptuni isolated from the gill lamellae of moribund mud crab (Scylla olivacea) is suspected to cause WSSV infection. Though there was morphological similarity between healthy and infected animals, the PCR result was positive for WSSV with an amplicon size of 941 base pairs. The amplicon was sequenced and the infection was confirmed. Hypertrophied nuclei, marginalised chromatin and virions of WSSV were observed in the nuclear cells and cytoplasm through transmission electron microscope (TEM). Histopathological study on the pedunculate barnacle showed basophilic inclusion bodies and hypertrophied nuclei. Further series of infectivity experiments were conducted to understand the virulence of the O. neptuni.