Fannon, Jessica May (2018) Deformed wing virus of honey bees – transmission, diversity and impact on honey bee development. PhD thesis, University of Warwick.

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Abstract

The spread of the parasitic mite, Varroa destructor (and the RNA viruses that it transmits between honeybees) is closely linked to increased overwintering losses and declining honeybee health. Deformed wing virus (DWV; Iflaviridae) a picorna-like single-stranded, positive-sense, RNA virus, is widespread in honeybees and usually present as a low level, asymptomatic infection. However, the transmission of DWV by Varroa to developing pupae causes markedly elevated virus levels and characteristic developmental abnormalities.

This work aims to further the understanding of DWV virulence and pathogenicity and reveal how this is linked to Varroa parasitism. Molecular techniques and a novel in vitro larval rearing system have been used to study how transmission route influences DWV accumulation and localisation in honeybee tissues. Additionally, the impact of Varroa on DWV levels and diversity on both a colony and a landscape level have been investigated, testing the hypothesis that a single virulent strain has a selective advantage when transmitted by Varroa.

The route of transmission does influence DWV infection and tissue location in developing honeybees, as shown by RNA-FISH. Injection of a dose of 10-4ng of viral RNA was sufficient to produce a pronounced DWV infection in the majority of individuals, whereas 300ng/larvae of DWV RNA needed to be mixed with larval food before any high viral load individuals were found. I also present novel work in which the relative expression levels of key developmental genes from the Homeobox and Ecdysone families are examined in honeybee larvae challenged by injection with DWV. In addition to this, a long-term study of viral diversity in the Ardnamurchan Peninsula, Scotland, illustrates how the viral landscape is affected by the introduction of the Varroa mite. Varroa colonisation led to a shift from a mixed population of viruses, predominantly VDV-like or VDV/DWV recombinants, towards a mainly DWV-like virus population.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QL Zoology Q Science > QR Microbiology > QR355 Virology S Agriculture > SF Animal culture
Library of Congress Subject Headings (LCSH):	Honeybee -- Viruses, Varroa destructor, Honeybee -- Parasites
Official Date:	December 2018
Dates:	Date Event December 2018 UNSPECIFIED
Institution:	University of Warwick
Theses Department:	School of Life Sciences
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Chandler, David ; Evans, David J. (Professor),
Format of File:	pdf
Extent:	iv, 226 leaves : illustrations, charts
Language:	eng

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