On the role of polychaetes (Dendronereis spp.) in transmission of white spot syndrome virus in shrimp ponds

White spot syndrome virus (WSSV) is the most devastating viral pathogen in shrimp production systems. WSSV is a generalist virus and infects members of several families of decapod crustaceans. Currently, WSSV has been found to be associated with 26 species of brackish water and marine shrimp, 15 species of fresh water shrimp and crayfish, 55 species of crabs and 10 species of lobster. The listing also includes 10 species of non-crustacean organisms, including polychaetes (Annelida), such as Dendronereis, and algae. Dendronereis spp. is a ubiquitous Nereid polychaete resident in shrimp ponds in Indonesia and part of the shrimps’ natural diet. Here we report on the possible role of Dendronereis spp. in the transmission of WSSV in shrimp pond systems. Field surveys in two research locations in Indonesia, Delta Mahakam (Kalimantan) and Semarang vicinity (Central Java), showed that association of WSSV with Dendronereis spp. is quite common, with a point prevalence of 44 ± 27% (± SD). WSSV was found to replicate in the gut of naturally-infected Dendronereis spp. as detected via immunohistochemistry using monoclonal antibodies to detect immunoreactive nuclei and via RT-PCR to detect the viral mRNA. This is the first evidence for a non-crustacean to be a natural replicative host for WSSV. WSSV was transmitted from naturally infected Dendronereis spp. to Litopenaeus vannamei (Boone 1931) through the oral route and further to new naïve shrimp showing that natural transmission of WSSV from polychaetes to shrimp is possible. In shrimp ponds WSSV infection in Dendronereis spp. correlated positively with Dendronereis spp. density, with proportion of WSSV infection in shrimp and the past incidence of white spot disease. Findings of the present study emphasize that resident benthic organisms in shrimp ponds, such as Dendronereis spp., can be a reservoir host of WSSV and may explain the persistence of WSSV in pond systems over time. However, further studies are required to obtain a better understanding of the relative importance of Dendronereis spp. in WSSV epidemiology in and beyond shrimp ponds. The significance of the findings may provide new insight on WSSV persistence in shrimp pond environments but also in white spot disease management.