an epidemiological study of listeriosis in dairy cattle

d) Presence of moles: Farmers were asked if they had seen mole hills in the fields where
hay, grass silage and straw were made. This was used as a binary variable.
e) Control of moles: If the mole hills were present, farmers were asked if they
controlled moles and the methods of controlling. These were used as binary variables
and categorical variables respectively .
3. 2. 4. Data analysis
A Yates corrected chi-square test was used to determine differences between
proportions. Odds ratios (OR) were calculated with 95% confidence limit (95%CL).
Categorical data such as duration of wilting, frequency of adding fresh bedding were
first treated as binary variables (the affect of presence or absence on the outcome) and
then categorised and analysed using chi-square tests (2xk contingency tables and chi
square for trend test using scores for each category) (Armitage and Berry, 1988).
3. 3. Results:
3. 3. 1. Univariate relationship between farm management practices and Listeriosis
in dairy cattle (Overall cases ):
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