Reduced transmission of IHHNV to Penaeus monodon from shrimp pond wastewater filtered through a polychaete-assisted sand filter (PASF) system

Abstract

A polychaete-assisted sand filter (PASF) can aid water recirculation systems for shrimp culture ponds by removing large amounts of nutrients and suspended solids and chemically treating wastewater. By ingesting and degrading organic matter, Perinereis helleri polychaetes reared in a PASF can accumulate and potentially remove infectious hypodermal and haemopoietic necrosis virus (IHHNV) present in wastewater from ponds rearing virus-infected Penaeus monodon shrimp. Reported here are data showing that filtering pond wastewater through a PASF reduces its potential to transmit IHHNV. The trial employed 3 groups of 4 tanks each containing 20 P. monodon randomly selected from a pond in which IHHNV was evident at moderate prevalence and low loads (IHHNV low-load Pond 2). Over a 2 week period, each tank group was supplied with wastewater from either the same pond (Pond 2) or Pond 1 in which IHHNV was 100% prevalent at ~104-fold higher infection loads, either directly or after being filtered through a PASF. IHHNV real-time qPCR data on total nucleic acid (TNA) extracted from pleopods of 35 P. monodon selected at random from each group identified an elevated IHHNV infection prevalence (91%) in shrimp tested from tanks supplied directly with wastewater from Pond 1. In comparison, IHHNV was detected at a much reduced prevalence and lower loads among shrimp from tanks supplied with wastewater from Pond 2 (33%) or from Pond 1 after it had been filtered through a PASF (31%). The IHHNV prevalence and load data indicate that a PASF can play a useful role in reducing the potential for shrimp pond wastewater to transmit IHHNV infection to naïve P. monodon.