Skip to main content

Table 1 Main epidemiological parameters with baseline estimates and ranges

From: A new bovine tuberculosis model for England and Wales (BoTMEW) to simulate epidemiology, surveillance and control

Parameter definition Symbol Estimate (Range) Source / Derivation
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.
  1. ‘Symbol’ is the symbol used in formulae. ‘Estimate (Range)’ indicates the baseline value, with a range indicating the potential uncertainty of the estimate, or a range dependent on location. Parameter values outside the stated ranges are likely to be associated with substantially worse model fit, or an infringement of reasonable constraints