|
Initial number of undetected infected herds
|
Z
|
4400 (1850–5050)
|
Fitted so that simulation matched the total number of breakdowns in 2008 within 100, i.e. between 4849 and 5049.
|
|
Number of holdings in England and Wales with infectious environmental reservoirs.
|
N
W
|
7840 (SD ± 73) (5500–14,000)
|
Determined by the regional probabilities that individual holdings will have infectious environmental reservoirs (PW).
|
|
Probability that individual holdings have infectious environmental reservoirs, dependent on a classification based on county and TB history.
|
P
W
|
0–0.828
|
The probabilities are fitted to local breakdown frequencies, see Fig. 1 and Methods.
|
|
Environment to cattle transmission rate per head of cattle at holdings with an infectious environmental reservoir.
|
h
|
0.0006 (0.0004–0.004) mth− 1
|
See Fig. 6.
|
|
Cattle to cattle transmission rate (per month) per infected animal in a herd of 200 cattle.
|
β
|
0.113 (0.10–0.14) mth− 1
|
Fitted to observed numbers of reactor animals at disclosing tests in HRA and LRA. Close to a previously published estimate [22].
|
|
Power law determining degree of density dependence of cattle-cattle transmission. (0 matches density dependence, while a value of 1 matches frequency dependence.)
|
q
|
0.5 (0.3–1.0)
|
Partial density dependence was demonstrated previously [22], but model outputs had low sensitivity to this parameter’s precise value.
|
|
Probability of a persistent infection at the end of a breakdown in herds > 300 cattle, given that infected cattle remained after the disclosing test or there was at least 1 additional reactor.
|
c
p
|
0.6 (0.3–0.9)
|
Fitted to the observed number of breakdowns detected by post breakdown tests, especially in the Edge and Low Risk regions. Probability was lower in smaller herds, see Additional file 1.
|
