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Table 4 Equations used for calculating the probabilities included in the model

From: Risk assessment as a tool for improving external biosecurity at farm level

  Yearly risk of introduction (R) via: Input parameters Equation
1 Individual live animals Herd prevalence (HP), within-herd prevalence (WHP), animals introduced yearly (n) R = 1 ‐ (1 ‐ (HP*WHP))n
2 Individual live animals, despite biosecurity HP, WHP, n, effect of quarantine (Q) R = 1 ‐ (1 ‐ (HP*WHP)*(1 ‐ Q))n
3 Animals in batches HP, WHP, n, yearly number of batches (batch) R = (1 ‐ (1 ‐ HP)batch) × (1 ‐ (1 ‐ WHP)n/batch)
4 Animals in batches, despite biosecurity HP, WHP, n, batch, Q R = (1 ‐ (1 ‐ HP)batch) × (1 ‐ (1 ‐ WHP)n/batch)*(1 ‐ Q)
5 Animal transport vehicles HP, probability of transmission via transport (trp), yearly transports (n) R = 1 ‐ (1 ‐ (HP*trp))n
6 Animal transport vehicles, despite biosecurity HP, TRP, n, effect of biosecurity routine (biosec) R = 1 ‐ (1 ‐ (HP*trp)*(1 ‐ biosec))n
7 Deadstock collector HP, probability of transmission via deadstock collector (dead), yearly collections (n) R = 1 ‐ (1 ‐ (HP*dead))n
8 Deadstock collector, despite biosecurity HP, dead, n, biosec R = 1 ‐ (1 ‐ (HP*dead)*(1 ‐ biosec))n
9 AI technician HP, probability of transmission via technician (AI), yearly visits (n) R = 1 ‐ (1 ‐ (HP*AI))n
10 AI technician, despite biosecurity HP, AI, n, biosec R = 1 ‐ (1 ‐ (HP*AI)*(1 ‐ biosec))n
11 Veterinarian HP, probability of transmission via veterinarian (vet), yearly visits (n) R = 1 ‐ (1 ‐ (HP*vet))n
12 Veterinarian, despite biosecurity HP, vet, n, biosec R = 1 ‐ (1 ‐ (HP*vet)*(1 ‐ biosec))n
13 Hoof trimmer HP, probability of transmission via hoof trimmer (hoof), yearly visits (n) R = 1 ‐ (1 ‐ (HP*hoof))n
14 Hoof trimmer, despite biosecurity HP, hoof, n, biosec R = 1 ‐ (1 ‐ (HP*hoof)*(1 ‐ biosec))n
15 All contacts Equations 1 (or 3), 5, 7, 9, 11, 13 R = 1 ‐ (1 ‐ Equ1)*(1 ‐ Equ5)*(1 ‐ Equ7)*(1 ‐ Equ9)*(1 ‐ Equ11)*(1 ‐ Equ13)
14 All contacts, despite biosecurity Equiations 2 (or 4), 6, 8, 10, 12, 14 R = 1 ‐ (1 ‐ Equ2)*(1 ‐ Equ6)*(1 ‐ Equ7)*(1 ‐ Equ10)*(1 ‐ Equ12)*(1 ‐ Equ14)