an epidemiological study of listeriosis in dairy cattle

On farm C pattern 1 was detected in the faecal and environmental isolates before
housing. This pattern was still common at the highest prevalence of infection but pattern
2 in faeces had appeared. In addition to pattern 1, patterns 5, 8 and 9 were also detected
in the environment.
On farm D pattern 5 was identified in animals and the environment prior to
housing. Pattern 6 was also detected in the environment, and patterns 1, 2 and 10 in
faeces. At the highest prevalence of infection, patterns 1, 2, 5 and 6 were detected in
faeces along with pattern 11. Pattern 5 was the only one detected in the environment.
On farm E, there was no common pattern in the environment and faeces prior to
housing. Pattern 6 in the environment and pattern 1, 5, 7 and 12 in faeces. At the peak
prevalence of infection, patterns 1 and 5 were still present in animals and pattern 6 had
also appeared. Pattern 6 was still present in the environment and patterns 1 and 7 were
also detected.
evaluated.
Repeat faecal and environmental isolates obtained from the farms were also
On farm A, repeat isolates from the same animal (animal 1) on 2 different visits,
6 visits apart (visit 1 and 7), had different patterns (pattern 5 and 1 respectively). 8
isolates obtained from two persistently L. monocytogenes positive animals (4 isolates
from each) were tested in an attempt to determine if the animals were excreting the
same strains. One animal had the same pattern but the second animal had 3 different
patterns (Figure 6. 10).
On farm B, 2 isolates from grass (visits 2 and 7) had the same pattern, pattern 5,
whereas 2 soil isolates (visit 7 and 9) and 2 isolates from bedding (visit 7 and 9) had
different patterns (1 and 5 and 5 and 6 respectively).
On farm C, repeat isolates from the same animal on consecutive visits (visits 2
and 3) had the same pattern, pattern 1. 2 isolates from silage (visits 4 and 5) also had the
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