Confirming validity measures of visual assessment of PaV1 infection in Caribbean spiny lobsters.

Abstract

Panulirus argus virus 1 (PaV1) affects wild populations of Caribbean spiny lobsters. PaV1 can be lethal but shows predilection for juvenile lobsters. Because P. argus is one of the most valuable fisheries around the wider Caribbean region, monitoring disease prevalence in local populations is desirable. Diseased lobsters are easily recognized by their milky hemolymph, but this sign only becomes evident in advanced stages of infection. Other methods have been developed to detect PaV1, but are less practical for long-term monitoring of patterns of infection in populations. A previous study estimated the validity measures (sensitivity and specificity) of detection of PaV1 infection by observed clinical signs against endpoint PCR assays, using a representative sample of lobsters comprising mainly subadults and adults from a commercial fishing area. In the present study, these validity measures were estimated in a similar manner for a different population comprising mainly juveniles from a protected nursery area. We obtained virtually the same sensitivity and specificity values (0.48 and 1, respectively) for observed clinical signs as in the previous study (0.51 and 1, respectively), confirming the validity of applying a simple 2× correction factor to monitor the patterns of PaV1 infection over time based on more easily conducted visual assessments of a representative sample of the population.