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) |