Abstract
Foot-and-mouth disease (FDM) is a disease of cloven-hoved animals with
high costs in animal welfare and for production of animal products. Up
to now transmission between farms in FMD-endemic areas has been given
little attention. Between farm transmission can be quantified by
distance independent transmission parameters and a spatial transmission
kernel indicating the rate of transmission of an infected farm to
susceptible farms depending on distance. The spatial transmission kernel
and distance-independent transmission parameters were estimated from
data of an FMD outbreak in Lumpayaklang subdistrict in Thailand between
2016 and 2017. The spatial between-farm transmission rate in
Lumpayaklang subdistrict was higher compared with spatial between-farm
transmission rate from FMDV in epidemic areas. The result can be
explained by the larger size of within-farm outbreak in endemic area due
to no culling. Inclusion of distance-independent transmission parameters
improved the model fit, which suggests the presence of transmission
sources from outside the area and spread within the area independent of
distance between farms. The remaining distance dependent transmission
was mainly local and could be due to over-the-fence transmission or
other forms of contact between nearby farms. Farm size on the kernel
positively effects the transmission rate, by increasing both infectivity
and susceptibility with increasing farm size. From the results, we
suggested more strict outbreak responses, as well as the outbreak
communication to the farmers to reduce the between-farm transmission.
Movement restrictions and enforced by checkpoints during the outbreak
can prevent the transmission from outside and the distance-independent
transmission within an area.