Date of Award

Spring 2022

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

School

Ocean Science and Engineering

Committee Chair

Eric A. Saillant

Committee Chair School

Ocean Science and Engineering

Committee Member 2

Reginald B. Blaylock

Committee Member 2 School

Ocean Science and Engineering

Committee Member 3

Stephen A. Bullard

Abstract

The obligate parasitic dinoflagellate Amyloodinium ocellatum causes amyloodiniosis in warm water marine fishes. The prolific parasite, which has a direct, three-stage life cycle, is highly infectious and can cause heavy losses in aquaculture. Prevention, biosecurity, and early detection are vital for control. In this work, microscopy and a loop-mediated isothermal amplification (LAMP) assay were compared for early diagnosis of A. ocellatum in cultured stocks, and the freeze tolerance of tomonts was assessed to determine if frozen wild fish used as fish food can serve as a potential vector for the parasite.

The lowest dinospore concentration that could be detected by the LAMP assay in water samples was 0.5 dinospores/L, while positive detections occurred only at 5 dinospores/L or higher when using LAMP or microscopy on gill samples. Thus, LAMP of water samples is a superior diagnostic tool. Simulations of replicated assays indicated that a 95% probability of detection was achieved with 10 replicated assays of water samples when the dinospore concentration is as low as 1 dinospore/L.

All tomonts frozen for either 0, 24, 36, 48, or 72 hrs sporulated in in vitro experiments. Dinospore production decreased as freeze duration increased. Heavy infections were produced in in vivo experiments from tomonts frozen for all freeze durations, but tomonts frozen for 72 hrs took longer to establish a heavy infection. Tomont viability was negatively correlated with freeze duration suggesting longer freezing durations may successfully inactivate tomonts, a hypothesis that will require further experimental evaluation.

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