Witcomb, Luci (2012) The in situ analysis of the microbial community associated with footrot of sheep. PhD thesis, University of Warwick.

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Abstract

Footrot (FR) is a highly infectious and debilitating disease of sheep, which has a
significant economic impact on the sheep farming industry, in the UK and worldwide
and causes significant suffering of sheep. Despite some recent advances, FR remains a
scientifically challenging disease to understand. To help improve our understanding of
disease pathogenesis, two culture-independent techniques were developed to examine
the microbial succession events between the causative agent, Dichelobacter nodosus
and an accessory agent, Fusobacterium necrophorum, the latter also postulated to be
involved in disease initiation. The two populations were monitored in relation to disease
initiation and progression during a longitudinal study and disease presentation in tissue
biopsies (in situ). Finally, the distribution of these two species of bacteria in the
environment was examined to highlight possible sources of infection.
The work in this thesis has demonstrated that FR is a disease where expression is related
to D. nodosus load present in the ovine interdigital space. D. nodosus (rpoD) load
increased from that on a healthy foot to one presenting with interdigital dermatitis (ID)
and feet with a higher D. nodosus (rpoD) load were more likely to go on to develop FR
one week later. FISH analysis of the D. nodosus population present within the epidermis
also revealed similar findings; D. nodosus cell counts increased during stages of ID, but
the organism was less frequently detected in biopsies from feet with FR. Suggesting that
ID might be the most infectious stage of the disease process. A fact that needs to be
highlighted to farmers to encourage treatment at this stage of disease. In contrast, F.
necrophorum (rpoB) load did not correlate with ID presentation or prior to the
development of FR, but increased the week of FR onset. FISH analysis also revealed
that F. necrophorum cell counts were higher in feet with FR than those with ID. It is
possible therefore that F. necrophorum may thrive in the altered environment of a foot
presenting with FR, possibly contributing to disease persistence and severity. Finally,
both pathogens were detected in a range of environmental samples from a farm with
endemic FR, highlighting possible sources of infection and material, which once
contaminated with D. nodosus and F. necrophorum may contribute to the spread of FR.
This study has provided an improved understanding of the microbial population
dynamics involved in the development of ID and FR in sheep, which may have
implications for control and treatment practices not only in the UK, but world-wide.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QR Microbiology S Agriculture > SF Animal culture
Library of Congress Subject Headings (LCSH):	Footrot in sheep -- Pathogenesis, Microbial populations
Official Date:	September 2012
Dates:	Date Event September 2012 Submitted
Institution:	University of Warwick
Theses Department:	School of Life Sciences
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Wellington, E. M. H. (Elizabeth M. H.), 1954- ; Green, Laura E.
Extent:	xx, 260 leaves : ill., charts
Language:	eng

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