Haemagglutination as a low-cost detection method for gill-associated virus and by inference, yellowhead virus in Penaeus monodon Fabricius, 1798

Abstract

A quantitative, low-cost test based on haemagglutination (HA) using chicken erythrocytes was developed to indicate the viral load of Australian yellowhead-like virus, gill-associated virus (GAV), in Penaeus monodon. The study tested the haemolymph, gill, lymphoid organ, heart, sub-cutaneous tissue, eye stalk, pleopods, uropods and the central nerve cord for agglutination activity in 100 prawns, with the haemolymph and gill tissue giving the highest end-point titres of 1:1370 and 1:361 respectively. The sensitivity of the test was demonstrated by testing two different populations of P. monodon, which showed a highly significant difference (P<0.001) in HA activity, indicating a difference in viral load. By testing three other penaeid prawn species (n=20), Penaeus esculentus, Penaeus merguiensis and Penaeus longistylis, and the crayfish Cherax quadricarinatus, it was demonstrated that natural agglutinins were not causing the high agglutination in the population of P. monodon being tested. It was also demonstrated that there was no effect of freezing and thawing of samples on HA activity. The speed and low cost of this test makes it a very useful tool, particularly in the developing world, for on-farm testing of penaeid prawns to indicate yellowhead virus and GAV loads which can contribute to management practices with respect to harvesting of ponds.