On-site detection of nodavirus in post larval (PL) stage of the giant prawn, Macrobrachium rosenbergii: A test to nip the problem in the bud

Macrobrachium rosenbergii nodavirus (MrNV) affects the larval, post-larval, and juvenile stages of M. rosenbergii, the giant freshwater prawn, causing white tail disease (WTD). With its high mortality, WTD is a severe threat to shrimp and prawn farming. We describe the development and optimization of an antibody-based lateral flow assay (LFA) for the early detection of MrNV in the post-larval (PL) stage of M. rosenbergii. The LFA parameters (viz., the detergent concentration, GNPs-antibody conjugate, antibody concentration applied to the test line and membrane porosity) were optimized using the design of experiment (L-9 orthogonal array). Under optimized conditions, MrNV could be detected within 20 min with high specificity, reproducibility, and sensitivity (LOD = 104 particles/ng of total RNA). In virus challenge experiments, MrNV could be detected on the seventh day of infection in the PL stage. LFA was validated using infected PL samples collected from the field (hatcheries and nurseries) (n = 80) in conjunction with `gold standard' qRT-PCR test. High sensitivity (100%) and specificity (90%) of LFA, with a Cohen's kappa coefficient of 0.936, suggested 'good agreement' between the developed LFA and qRT-PCR. The developed LFA has an immense potential of averting losses by rapid detection of MrNV at PL stage in M. rosenbergii.