Due to the small size of the juvenile prawns, the inoculum was both diluted and reduced in volume so that the mortality due to the injection procedure would be minimised. This may have reduced the mortality rate and the number of positive PCRs from the experimental groups. Other explanations for the limited effect of the inoculum are possible, such as the life stage of the prawns, virulence of the virus and the sensitivity of the PCR. Further research should disclose the
probable causes.