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The pathogenesis of epizootic ulcerative syndrome (EUS) with particular reference to factors potentially influencing outbreaks of the disease in the Philippines

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Catap, Elena Siron (2001) The pathogenesis of epizootic ulcerative syndrome (EUS) with particular reference to factors potentially influencing outbreaks of the disease in the Philippines. PhD thesis, University of Tasmania.

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Abstract

Epizootic ulcerative syndrome (EUS) outbreaks in the Philippines had been
consistently associated with periods of decreasing and fluctuating water
temperature usually after the rainy season. Therefore, one of the main objectives
of this study was to examine the influence of low and highly fluctuating
temperature on the pathogenesis of the disease based on the histopathological and
epidermal changes. Also, the influence of water temperature variations on the
nonspecific immune responses of a fish exposed to Aphanomyces invadans was
determined. Moreover, the efficacy of four therapeutic substances to enhance the
defense mechanisms of susceptible fish against EUS was assessed.
A model of the sequential pathology of EUS was developed and described in
three spot gourami Trichogaster trichopterus and sand whiting Sillago ciliata.
Both species of fish exhibited histopathological changes typical of EUS, such as
chronic granulomatous response and inflammatory cell infiltration in the muscle
and skin tissues, at day 8 post-inoculation of 55 to 70 spores/fish. From the
results of comparative granuloma counts and percentage of cellular infiltration in
a sampled lesion area using image analysis, it was shown that the three-spot
gouramis developed a more vigorous response than the sand whiting.
Based on the EUS model, the effects of either rapid or gradual decrease in
temperature on the histopathology of EUS in sand whiting was documented.
Qualitative and quantitative histopathological examinations revealed a marked
delay in the inflammatory response of fish maintained at low temperature. EUS
lesions were also induced in skin-abraded three-spot gouramis exposed to motile
A. invadans zoospores, with higher mortality in fish subjected to daily
temperature variations (26 °C to 19°C) than in fish held at 26°C.
Histopathological examination also revealed minimal inflammatory cell
infiltration and delayed mycotic granuloma formation with extensive tissue
damage in temperature-stressed fish.
Fish oil, L-cysteine ethyl ester, yeast glucans and levamisole were trialled as
prophylactics against EUS. Only yeast glucans and levamisole gave encouraging
results.
Results from this study showed that low and fluctuating temperature could affect
the host's defense mechanisms against EUS and that preventive measures should
be aimed at the maintenance of the epidermal integrity and improvement of the
nonspecific immune response of fish.

Item Type: Thesis (PhD)
Keywords: Communicable diseases in animals, Fishes
Copyright Holders: The Author
Additional Information:

Thesis (PhD)--University of Tasmania, 2001. Includes bibliographical references

Date Deposited: 25 Nov 2014 00:50
Last Modified: 11 Mar 2016 05:54
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