Reeling in the truth: Drivers of aquatic infection & control

MacAulay, Scott 2023. Reeling in the truth: Drivers of aquatic infection & control. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Freshwater habitats are facing high extinction rates, due to anthropogenic influences from habitat loss and over-exploitation. Combine this with the threat posed by infectious disease, and all freshwaters, be they wild, aquaculture or ornamental, require aid to mitigate biodiversity loss. This PhD sought to assess the drivers of aquatic infection and control, with the goal to create a resource to aid management of freshwater systems. Assessing aquatic disease control was accomplished through a literature review of aquatic diagnostics, where the past, present and future methods of aquatic diagnostics were collated and assessed under four pillars of: high sensitivity, specificity, rapid diagnosis, and cost-effectiveness. Once the scope of aquatic diagnostics was assessed, the next step was to ensure and optimise a method for adequate supplies of aquatic parasites, to be available for experimental studies. This led to the testing of two storage methods on the aquatic parasite Saprolegnia parasitica, mineral oil immersion and cryopreservation. Both methods were effective for short- and mid-term (1 – 50 days) preservation, particularly cryopreservation, which led to experimental studies conducted on the drivers of infection. Drivers were divided into two broad categories, natural and non-natural. For natural drivers, temperature and light were assessed. First, in how they impact the in vitro growth of S. parasitica, where it was found that growth rate (regardless of strain) was highest at 25°C. Light was found to impact different strains differently, with the common impact being reduced growth when exposed to constant light. This led to assessment of light impacts on Gyrodactylus turnbulli. Here, the impacts of light exposure on both natural and experimentally infected guppies (Poecilia reticulata) were assessed, revealing greater maximum parasite burdens for fish exposed to constant light. Moving to non-natural drivers, pollutants specifically microfibres were assessed. Three fibre types, polyester, cotton and bamboo, were evaluated on their impacts on guppy-G. turnbulli infections and off-host survival of G. turnbulli. Polyester was found to increase maximum parasite burdens and hasten parasite mortality, whilst bamboo had significantly lower parasite burdens and no impact on parasite survival. This prompted further investigation into bamboo fibres and their associated dye, where no negative impacts were found in regard to parasite burdens, but respirometry was impacted. The data provided throughout this thesis furthers our understanding of the drivers and control of aquatic infectious disease.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Biosciences
Subjects:	Q Science > Q Science (General)
Funders:	Biotechnology and Biological Sciences Research Council (BBSRC) South West Biosciences Doctoral Training Partnership (SWBio DTP), UK Environment Agency
Date of First Compliant Deposit:	28 May 2024
Date of Acceptance:	28 May 2024
Last Modified:	28 May 2024 12:20
URI:	https://orca.cardiff.ac.uk/id/eprint/169213

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