Abstract
We describe results from a panel study in which pigs from a 17-sow
African swine fever (ASF) positive herd in Thái Bình province, Vietnam
were followed over time to record the date of onset of ASF signs and the
date of death from ASF. Our objectives were to: (1) fit a
susceptible-exposed-infectious-removed disease model to the data with
transmission coefficients estimated using Approximate Bayesian
Computation; and (2) provide commentary on how a model of this type
might be used to provide decision support for disease control
authorities For the outbreak in this herd the median of the average
latent period was 10 days (95% HPD [highest posterior density
interval]: 2 to 19 days) and the median of the average duration of
infectiousness was 3 days (95% HPD: 2 to 4 days). The estimated median
for the transmission coefficient was 3.3 (95% HPD: 0.4 to 8.9)
infectious contacts per ASF-infectious pig per day. The estimated median
for the basic reproductive number, R0, was 10 (95% HPD:
1.1 to 30). Our estimates of the basic reproductive number
R0 were greater than estimates of R0 for
ASF reported previously. The results presented in this study may be used
to estimate the number of pigs expected to be showing clinical signs at
a given number of days following an estimated incursion date. This will
allow sample size calculations, with or without adjustment to account
for less than perfect sensitivity of clinical examination, to be used to
determine the appropriate number of pigs to examine to detect at least
one with disease. A second use of the results of this study would be to
inform the equation-based within-herd spread components of stochastic
agent based and hybrid simulation models of ASF.