3.6 Epidemiological relevance of the network.
The recorded number of CSF outbreaks in each year was 2017 (n=39), 2018
(n=60), and 2019
(n=35).
Only 75 of 134 outbreaks were identified in the network, 9 were excluded
because they were movements to abattoirs, and 66 were final outbreaks
with 204 immediate neighbours.
The k-test results showed that infected premises were connected to a
mean of 0.246 other infected premises in the 3-year cumulative network
(mean test value was 0.0013) (Fig. 11); therefore, the k-test rejected
the null hypothesis that cases were strewn in the network
(p<0.001). CSF outbreaks were connected with annual means of
0.13 (p=0.002) and 0.38 (p<0.001) positive premises in 2017
and 2018. The mean values of the permutations were 0.0027 and 0.0084 for
2017 and 2018, respectively. The year 2019 showed no significant
relationships.
Figure 11. (A) K-test graphical results where the blue region under the
curve represents the null distribution of the k-statistic when the
location of the infected nodes was randomised on the network. The red
line indicates the number of observed cases with one step of a case. (B)
Representation of the CSF outbreaks (66 red nodes in the network) and
limited only to their immediate neighbours for visualisation purposes
(Fruchterman-Reingold layout).