White spot syndrome virus in decapods from Mississippi Sound, USA, and susceptibility of Palaemonetes pugio and Uca panacea to a Chinese isolate

The presence and quantity of white spot syndrome virus (WSSV) was surveyed using TaqMan real-time PCR to assess the extent of the virus in Mississippi Sound, USA. A total of 3577 wild decapods comprising 11 species was collected between November 2012 and August 2015: WSSV was present in 10 of the 11 species. Prevalence ranged from 5.1% in Uca rapax to 38.8% in U. spinicarpa. Viral load ranged from 1.8 to 7.3 log10 copies of WSSV µg-1 total DNA. Two Gulf species, Palaemonetes pugio and U. panacea, were injected with a series of doses of a virulent WSSV isolate from China to determine relative susceptibility and virulence because continuing translocation of highly pathogenic isolates of WSSV poses risk to native species. Survival was 0-65% for P. pugio and 5-60% for U. panacea. Median survival time was lower for P. pugio than U. panacea at all doses. Mean (±SD) lethal load was 9.0 ± 8.9 log copies of WSSV µg-1 total DNA in P. pugio and 8.2 ± 8.3 in U. panacea. Mean viral load in survivors was higher in U. panacea than in P. pugio (5.8 ± 6.1 vs. 3.2 ± 3.0 log copies of WSSV µg-1 total DNA); mean viral load was lower in wild individuals of those species (2.9 ± 3.2 for P. pugio and 4.9 ± 5.0 for U. panacea). U. panacea is potentially more tolerant of WSSV than P. pugio and may serve as an important reservoir host in the community.