Date of Award

Fall 12-2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ocean Science and Technology

Committee Chair

Jeffrey M. Lotz

Committee Chair Department

Ocean Science and Technology

Committee Member 2

Darrell J. Grimes

Committee Member 2 Department

Ocean Science and Technology

Committee Member 3

Wei Wu

Committee Member 3 Department

Ocean Science and Technology

Committee Member 4

Reginald B. Blaylock

Committee Member 4 Department

Ocean Science and Technology

Abstract

Ever since the first outbreaks of White spot syndrome virus (WSSV), which causes White Spot Disease (WSD), in Asia in the early 1990s, the pathogen has been a major constraint to the profitability of the shrimp aquaculture industry across the globe. WSSV has a broad host range and is routinely detected in wild decapod crustaceans. In the present study, two common species in the tidal salt marsh along the northern coast of the Gulf of Mexico, the daggerblade grass shrimp (Palaemonetes pugio) and the Gulf sand fiddler crab (Uca panacea), were investigated for their role as reservoirs of WSSV and for the possible consequences of WSSV on their population dynamics. From 2013 to 2015, 1884 individuals of P. pugio and 1280 individuals of U. panacea were collected and screened for WSSV. The overall prevalence of WSSV in P. pugio and U. panacea was 7.27% and 12.97%, respectively. From experimental bioassays, the LD50 of WSSV for P. pugio at 5 dpi was 8.24×107 WSSV genome copies g-1 of body weight or 2.45×107 WSSV genome copies/grass shrimp, whereas the LD50 of WSSV for U. panacea at 14 dpi was 1.67×108 WSSV genome copies g-1 of body weight or 2.55×108 WSSV genome copies/fiddler crab. Experimental transmission of WSSV-China isolate to P. pugio occurred when exposed to infected living P. pugio (β1,1 = 0.03 d-1), infected living U. panacea (β1,2 = 0.02 d-1), infected P. pugio carcasses (χ1,1 = 0.08 d-1), and infected U. panacea carcasses (χ1,2 = 0.03 d-1). However, no WSSV transmission was observed when U. panacea was exposed to infected living or infected carcasses of either of the two species. Virulence of WSSV was higher in P. pugio (α1 = 0.014 d-1) than in U. panacea (α2 = 0.00). The decomposition of WSSV infectivity in carcasses of the two species was rapid (δ = 1 d-1). The basic reproduction number (R0) as calculated from single-host WSSV epidemic population models was 2.22 for P. pugio and 6.71 for U. panacea. R0 from a two-host WSSV epidemic community model, including both P. pugio and U. panacea, increased to 17.09.

ORCID ID

0000-0002-9837-8516

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