an epidemiological study of listeriosis in dairy cattle

manner in which silage plays a role is little known. Improper silage making practices
have been suggested as an explanation for this association (Wilesmith and Gitter 1986)
but more work is required to ascertain the role of silage. Stress of housing, pregnancy
and weather have been considered as predisposing factors (Hyslop 1975). Poor flock
management has also been associated with disease (Meredith and Schneider 1984).
However no data is available to quantify these factors.
A postal questionnaire survey was designed to determine the frequency of
clinical listeriosis and the relationship between farm management factors and
occurrence of clinical listeriosis in dairy cattle. The latter is described in this chapter.
3. 2. Materials and Methods:
3. 2. 1. Study design:
Chapter 2.
Information about the questionnaire design and conduct of study is given in the
In studying the relationship between the occurrence of clinical listeriosis and
farm related management factors, only those cases reported between July 1994 and June
1995 were considered. 5 outcome variables and 5 groups of predictor variables were
used.
3. 2. 2. Outcome variables:
(i) Total number of cases (Overall cases): Farms that reported clinical listeriosis in
cattle of any age.
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