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Gyrodactylid biology, transmission and control

Schelkle, Bettina 2012. Gyrodactylid biology, transmission and control. PhD Thesis, Cardiff University.
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Infectious disease in aquaculture is omnipresent, but traditional treatments used against the causative agents often have broad anti-parasitic properties, are not 100 % efficacious, are toxic to humans, fish and the environment, and successful application is challenging. Hence, integrated disease management that combines an understanding of parasite life history and host welfare with treatment is highly recommended. This thesis examined the life history characteristics of a ubiquitous genus of fish ectoparasites, Gyrodactylus species, and tested the efficacy of botanical treatments against gyrodactylids using the guppy (Poecilia reticulata) infected by G. turnbulli or G. bullatarudis as model, with the aim to work towards an integrated management plan for gyrodactylosis in the ornamental fish industry and the hobbyist market. The experiments conducted have shown that (1) gyrodactylids engage in sexual reproduction and on a population level show hybrid fitness and/or inter-strain competition when diverged genotypes are recombined; (2) parasite transmission is mainly driven by direct contact with potential hosts and on dead fish or after detachment gyrodactylids have a window of opportunity to re-attach of over 20 h; (3) extreme habitats provide guppies with a refuge from microbial and gyrodactylid infections in natural populations; (4) anti-parasitic treatment efficacy may be species specific using traditional methods; and (5) salt, garlic, cajuput oil and a combination treatment of the two commercially available treatments Melafix® and Pimafix® are efficacious alternatives for broad anti-parasitic aquarium treatments against gyrodactylids. Due to their efficient reproduction, gyrodactylids are unlikely to be eradicated, as just a single, pregnant worm can trigger a new disease epidemic. However, combining the knowledge on pathogen life history characteristics and host-parasite interactions with effective treatment application will reduce evolutionary pressures on the pathogen and slow its virulence evolution. Overall, this increases the time available for treatment efficacies to be maintained in a manner which corresponds with new drugs being developed as treatment resistance arises.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Biosciences
Subjects: Q Science > QL Zoology
Funders: Biotechnology and Biological Research Council, WALTHAM Centre for Pet Nutrition
Date of First Compliant Deposit: 30 March 2016
Last Modified: 23 Mar 2017 03:58

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