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| This PhD thesis, entitled Investigating the epidemiology of
Bovine Digital Dermatitis: causality, transmission and infection
dynamics, presents the outputs and original findings of field research
submitted by Willem Daniel Vink to the
University of
Liverpool, September 2006. It was conducted as part of a
Defra-funded project entitled Control of
digital dermatitis in cattle: understanding transmission and spread of
disease. |
| The author asserts the intellectual rights to this work. If you wish
to utilize, disseminate, cite from or otherwise apply this material, please
acknowledge this appropriately, or contact daan42@liv.ac.uk. The thesis can be downloaded as a
PDF by clicking on the icon. A synopsis of the individual chapters is available
by using the menu at left. A BibTeX citation reference is given
here. |
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Preface |
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The stated objective of this project, which ran
from October 2002 to September 2006, was to investigate the origin and route of
transmission of pathogenic, bovine digital dermatitis-associated
Treponema spp. bacteria on UK dairy farms.
The project took
a multidisciplinary approach, combining epidemiology with microbiology as a
means of advancing our understanding of the disease.
| A. Epidemiological
studies |
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1. |
Perform field
studies on representative dairy farms in Cheshire, namely a cross-sectional
study followed by a longitudinal study. |
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2. |
Improve case
definition, primarily through investigation of the diagnostic and screening
properties of a treponemal serological test (ELISA). |
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3. |
Use serology
to assess the distribution of antibodies in the farm populations, determine
seropositivity rates and estimate the true prevalence of disease. |
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4. |
Identify cow-,
group- and farm-level risk factors. |
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5. |
Formulate and
parameterize appropriate statistical and mathematical models of infection
dynamics, and use these models to explore putative control strategies.
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| B. Microbiological
studies |
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1. |
Further
develop and refine techniques for culture and isolation of Treponema
spp. from the dairy farm environment. |
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2. |
Identify and
characterize these and other bacterial species isolated from bovine digital
dermatitis lesions. |
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3. |
Perform
phylogenetic analysis to identify spirochaete genotypes associated with the
disease, and determine prevalence of pathogenic genotypes in relation to
severity. |
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4. |
Identify the
source(s) of Treponema spp. in the farm environment, including which cow
tissues harbour these bacteria in normal and diseased cows. |
The
following outputs of the epidemiological studies are available on this website:
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1. |
A contextual
literature review, with
specific emphasis on the epidemiology of the disease, and a discussion of
putative causal mechanisms of BDD. |
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2. |
A discussion
of the molecular
epidemiology, which elucidates the disease determinants associated
with bovine digital dermatitis. |
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3. |
Detection of
disease on the individual animal level through investigation of various
diagnostic protocols
for case definition, including the development of a Treponema spp. ELISA
and formulation of a Bayesian model which allows inferences about the
predictive probability of infection to be made on the basis of a serological
result. |
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4. |
Exploratory
data analysis and statistical modelling of a cross-sectional study dataset, which enables
investigation of group- and herd-level disease distribution and prevalence, and
association of BDD with various risk factors. |
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5. |
Investigation
of temporal trends in BDD, including transmission dynamics, through exploratory
data analysis and statistical modelling of a longitudinal study dataset. |
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6. |
Work on
development of a mathematical
simulation model, which was formulated and parameterised using the
outputs of our field studies. |
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©
Willem Daniel Vink 2006 |
