ECOLOGY OF A FATAL BLUE CRAB VIRUS: DETECTION, RANGE, AND PREVALENCE OF CALLINECTES SAPIDUS REO-LIKE VIRUS

Abstract

Callinectes sapidus reo-like virus (RLV) is a fatal to blue crabs and consistently found within the Chesapeake Bay. Development of a sensitive and reliable RT-qPCR assay permitted a precise assessment of RLV prevalence in crabs captured from locations near and far from soft-shell crab production sites. Viral prevalence was temporally and spatially highly variable, but outbreaks of RLV appeared to be localized to an area of 1 - 2 km2. When significantly different between sites, higher prevalence was observed near soft-shell crab production. RLV prevalence was not correlated with crab characteristics, with the exception of larger mean carapace width for infected crabs. Sequences of RLV PCR products were used to compare genotypes of outbreak and non-outbreak infections. Identical genotypes were found in outbreaks from the middle Chesapeake Bay and Long Island, NY. Together, the prevalence and genetic data are consistent with RLV outbreaks being caused by focal spread of the virus through a local population.