RESERVOIRS OF White spot syndrome virus IN THE NORTHERN GULF OF MEXICO  

White spot syndrome virus (WSSV) is one of the most significant crustacean pathogens and a major impediment to the profitability of crustacean culture. As interest in crustacean farming in the US increases, e.g. blue crabs (soft-shell shedding, and pond culture), white shrimp, spiny lobster (Panulirus argus), and freshwater prawns, WSSV will be a significant impediment to the growth of those industries. Therefore, identifying potential reservoir hosts among wild native crustacean species will be vitally important to preventing spread into US to aquaculture.  WSSV is thought to have originated in southeast Asia and was first reported in the U.S. in coastal shrimp aquaculture facilities in Texas and South Carolina in 1995.  The virus has persisted in U.S. coastal waters since 2005.  WSSV also has emerged to severely affect the domestic crawfish farming industry can now be found in wild crawfish. We undertook to evaluate the distribution and prevalence of WSSV in wild decapod crustaceans in the northern Gulf of Mexico. We have observed sporadic occurrence of WSSV in wild penaeid shrimp in the northern Gulf of Mexico since 1997; however, our routine surveys of decapods suggest a significant increase in WSSV subsequent to 2010. In surveys we conducted in Mississippi and Louisiana from 2013 through 2015 we found WSSV in the blue crab (Callinectes sapidus) (8.3%, n=12), purple marsh crab (Sesarma reticulatum) (10.0%, n=20), Gulf mud fiddler crab (Uca longisignalis) (50.0%, n=72), panacea sand fiddler crab (U. panacea) (10.8%, n=1404), mudflat fiddler crab (U. rapax) (23.0%, n=88), spined fiddler crab (U. spinicarpa) (35.7%, n=98), red-jointed fiddler crab (U. minax) (22.7%, n=22), squareback marsh crab (Armasus cinereum) (26.7%, n=30), daggerblade grass shrimp (Palaemonetes pugio) (9.4%, n=1244), and white shrimp (Litopenaeus setiferus) (20.0%, n=40).      

In controlled experiments conducted at USM/GCRL, we observed 100% mortality rates in the commonly cultured L. vannamei and the three penaeid shrimp species native to the Gulf of Mexico: white shrimp, brown shrimp (Farfantepenaeus aztecus), and pink shrimp (Farfantepenaeus duorarum) after 2−5 days of being inoculated with WSSV. Similarly we observed 100% mortality of blue crabs, following injection exposure.  Mean time to death was 51.8 h.