Date of Award

Summer 8-5-2019

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Science

First Advisor

David Weese

Second Advisor

Indiren Pillay

Third Advisor

Gregory Glotzbecker

Abstract

Aquaculture has become a major food source for many countries and continues to grow each year. However, many of the fishes that are farmed are susceptible to pathogenic infections such as Francisellosis, a bacterial infection that contributes to disease and high mortality rate in many populations of farmed and wild fish around the world. In 1994, feral and farmed populations of tilapia (e.g. Oreochromis mossambicus) on Oahu, Hawaii were found to be infected with a novel Francisellosis strain, Francisella noatunensis subsp. orientalis (Fno). To prevent the spread of this pathogen, the Hawaii Department of Aquaculture (HDOA) initiated a ban on the exportation of tilapia to other Hawaiian Islands. To evaluate the effect of this ban and determine the prevalence of Fno throughout Hawaii, the goal of this study was to investigate the occurrence of Fno infections in wild tilapia on Oahu and the other islands using histological as well as molecular methods. Tissue samples from 222 tilapias collected on the islands of Oahu, Molokai, Kauai, Maui, and Molokai were screened via histology for evidence of granulomas and by real-time PCR for Fno bacterial DNA. Histological and molecular evidence of Fno infections were found in fish from Oahu, Kauai and Maui. This is the first report of Fno from the islands of Kauai and Maui suggesting that the quarantine efforts were not successful. However, we cannot rule out the possibility that infected fish were imported from outside of Hawaii. These findings have the potential to assist in the development of a disease management program for Fno that may result in an overall improvement in tilapia production throughout Hawaii.

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