Modelling the field personnel resources to control foot-and-mouth
disease outbreaks in New Zealand
Abstract
The objective of the study was to simulate New Zealand’s foot-and-mouth
disease (FMD) operational plan to determine personnel requirements for a
FMD response and understand how the numbers of frontline staff available
could affect the size and duration of FMD outbreaks, when using
stamping-out (SO) measures with or without vaccination. The model
utilized a national dataset of all known livestock farms. Each
simulation randomly seeded infection into a single farm. Transmission
mechanisms included direct and indirect contacts, local and airborne
spread. Prior to each simulation, the numbers of personnel for
front-line tasks were set randomly. In a random subset of simulations,
vaccination was allowed to be deployed as an adjunct to SO. Front-line
tasks included contact tracing, surveillance of at-risk farms,
depopulation and vaccination using teams comprising personnel of the
different types required by New Zealand’s operational plans. The effect
of personnel numbers on the size and duration of epidemics were explored
using machine learning methods. In the second stage of the study, using
a subset of iterations where numbers of personnel were unconstrained,
the number of personnel used each day were quantified. When personnel
resources were unconstrained, the 95 th percentile and
maximum number of infected places (IPs) were 78 and 462 respectively,
and the 95 th percentile and maximum duration were 69
and 217 days respectively. However, severe constraints on personnel
resources allowed some outbreaks to exceed the size of the UK 2001 FMD
epidemic which had 2026 IPs. The number of veterinarians available had a
major influence on the size and duration of outbreaks, while the
availability of other personnel types did not. A shortage of
veterinarians was associated with an increase in time to detect and
depopulate IPs, allowing for continued transmission. Emergency
vaccination placed a short-term demand for additional staff at the start
of the vaccination programme, but the overall number of person days used
were similar to SO-only strategies. This study determined the optimal
numbers of front-line personnel required to implement the current
operational plans to support an FMD response in New Zealand. A shortage
of veterinarians was identified as the most influential factor to impact
disease control outcomes. Emergency vaccination led to earlier control
of an FMD outbreak, but also resulted in a short-term spike in demand
for personnel. A successful response needs to have access to sufficient
personnel, particularly veterinarians, trained in response roles and
available at short notice.