Proceedings of the 10th International Colloquium on Paratuberculosis

from <strong>the</strong>ir dam, separate colostrum collecting and feeding to <strong>the</strong> calves by <strong>the</strong> calf manager and
improvements in general sanitation throughout <strong>the</strong> calf feeding program and housing. The
Johne’s Control Program also included <strong>the</strong> discontinuation <strong>of</strong> feeding <strong>the</strong> milking herd TMR
overages to <strong>the</strong> young stock herd. These measures resulted in a decrease in Johne’s
prevalence at this farm. In <strong>the</strong> data analysis we <strong>the</strong>refore made a comparison between <strong>the</strong> two
different time blocks. Calves born before and after January 1,1999 were distinguished and
analyzed separately to evaluate influence <strong>of</strong> management changes to control Johne’s disease
at this farm.
RESULTS AND DISCUSSION
Figure 1 shows <strong>the</strong> change in incidence and prevalence from 1995 to 2002. Incidence <strong>of</strong>
infections was initially high, but dropped dramatically after 1998 when a Johne’s control program
was implemented. Prevalence also dropped but less dramatically. Although it is a single farm
observation, it appears that <strong>the</strong> implementation <strong>of</strong> a Johne’s control strategy had a dramatic
impact on incidence <strong>of</strong> new infections. Prevalence dropped also, but because <strong>of</strong> <strong>the</strong> lagging
effect <strong>of</strong> incident infections from previous years, <strong>the</strong> drop in prevalence was not as steep
compared to <strong>the</strong> drop in incidence. Fecal shedding prevalence was a function <strong>of</strong> overall
infection prevalence and showed <strong>the</strong> same gradual decrease.
Significant clusters are presented in Table 1. We did not find any cluster with a window
size <strong>of</strong> 4 days. There were a total <strong>of</strong> 8 clusters with a window size <strong>of</strong> 10 days, 4 clusters with a
window size <strong>of</strong> 60 days and <strong>the</strong> same number <strong>of</strong> clusters with a window size <strong>of</strong> 90 days, finally,
two clusters with a window size <strong>of</strong> 120 days were observed. The data were separately analyzed
for <strong>the</strong> births before January 1, 1999 and <strong>the</strong> births after this date. These split analyses showed
that all birth clusters occurred before January 1, 1999. No significant clusters <strong>of</strong> MAP infection
were shown to be present after this date.
0.6
0.5
0.4
0.3
0.2
0.1
0
Prevalence
Fecal shedding
Incidence
1995 1996 1997 1998 1999 2000 2001 2002
Fig. 1 Prevalence, Incidence and fecal shedding at <strong>the</strong> study farm.
Table 1. Significant MAP infection birth clusters in <strong>the</strong> time frame from 1989 to 2003. Clusters <strong>of</strong>
different window size are presented. All clusters are shown and <strong>the</strong> mean number <strong>of</strong> cases and
<strong>the</strong> total cluster size <strong>of</strong> <strong>the</strong> clusters are presented.
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