an epidemiological study of listeriosis in dairy cattle

) Vaccine use: Vaccinating animals against Leptospirosis was also associated with an
increased risk of disease (OR 1.88, CL 1.12-3.15) (Table 3. 15).
c) Mole control: Controlling moles was associated with a decreased risk of reporting
disease (OR 0.49, CL 0.29-0.83) (Table 3. 15).
3. 3. 4. The univariate relationship between farming practices and cases of
Listeriosis with silage eye (iritis).
65 of the respondents reported cases of Listeriosis with silage eye on their farms.
17 of the farm level predictor variables were associated with disease (silage eye).
(i) Herd size:
As the herd size in milking cows increased the risk of disease also increased.
This was only statistically significant for herd sizes reported in July 1994 (Table 3. 16)
Table 3. 16. The univariate relationship between herd sizes and silage eye
June 1995 July 1994
Herd
sizes n
Y N OR P value x Y N OR P value X
M. cows 100 18 198 2.21 0.06 17 195 2.48 0.04
n number of animals, R reference category, X X 2 for trend, Y number of farmers reporting cases, N
number of farmer not reporting cases, OR, Odds Ratio.
(ii) Feeding practices:
a) Type of forages: Feeding maize silage was associated with an increased risk of
reporting silage eye cases (OR 2.12, CL 1.21-3.70) (Table 3. 17).
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