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The impact of respiratory disease on production in the pig industry in Great Britain
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Evans, Charlotte Marie (2010) The impact of respiratory disease on production in the pig industry in Great Britain. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b2338639~S15
Abstract
This thesis presents research on the epidemiology of respiratory
diseases in
pig
herds in GB
and their impact
on pig morbidity and mortality.
The
role of
management, characteristics of the
herd, presence of multiple pathogens and
control and elimination strategies were considered.
Questionnaires were completed
by
veterinarians that attended 116 pig
herds in
GB. Pathogens were clustered on
individual farms,
suggesting similar risk
factors
for infection /
persistence. Management factors
were
investigated for their
association with the within and between-herd variability
in
pig antibodies to
porcine reproductive and respiratory syndrome virus
(PRRSV) in 103 pig
herds.
Factors that
were
important included
close proximity
to other pig
herds, having
>250
sows and not
isolating
purchased stock or not
isolating for long
enough.
Considering the possible
fade out of
PRRSV, the within-herd transmission
dynamics were
investigated using a mathematical model.
There was a high
frequency of
fade out
in breeding pigs
before virus reached young stock and
increased persistence in
young stock,
in large herds, herds with
increased contact
between age groups and herds that had frequent re-introduction of virus.
Results
provided evidence for
apparent erratic
behaviour of
PRRSV
within and between
herds.
Mathematical
models were also used to
investigate
the range of
impacts
of
PRRSV
on
disease in
a
herd
and to test strategies for
control and elimination.
PRRSV was
difficult to eliminate without
targeting both rearing pigs and sows.
Rapid
vaccination of sows once there was an
increase in
preweaning still
births
reduced the
spread of virus
to
rearing pigs.
Results highlighted
that
in
areas of
GB
where
the density
of pigs
is low it
might
be possible to control
PRRSV
through elimination.
In larger herds in
pig
dense
regions elimination might
be difficult
and control might give more stability.
The
long-term benefits of elimination will
depend
on
(re)-introduction
of virus
from
within and outside the herd but
significant
improvements in
production might not
be observed unless several respiratory pathogens are eliminated
from
a herd.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QL Zoology | ||||
Library of Congress Subject Headings (LCSH): | Respiratory organs -- Diseases -- Epidemiology, Porcine reproductive and respiratory syndrome, Swine -- Diseases -- Epidemiology, Swine -- Diseases -- Mathematical models, Swine -- Productivity | ||||
Official Date: | February 2010 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Biological Sciences | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Green, Laura E. ; Medley, Graham | ||||
Sponsors: | Great Britain. Dept. for Environment, Food & Rural Affairs (DEFRA) ; Biotechnology and Biological Sciences Research Council (Great Britain) (BBSRC) ; British Pig Executive (BPEX) | ||||
Extent: | xvii, 162 leaves : ill., charts | ||||
Language: | eng |
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