Fig 1.
Set up for the epidemiological model in the African horse sickness (AHS) control area.
(A) Map of the AHS control area overlayed with a grid made up of 153 cells in which the model was run. The highlighted cell is the example simulation cell. Municipalities within the study area were CPT = City of Cape Town, SWL = Swartland, DRK = Drakenstein, STB = Stellenbosch, OVS = Overstrand, TWK = Theewaterskloof, BRV = Breede Valley, SDB = Saldanha Bay Bay, BGR = Bergrivier, CED = Cederberg, WIT = Witzenberg, LGB = Langeberg, CPA = Cape Agulhas, SWD = Swellendam. (B) Schematic diagram showing the transmission pathways of the AHS model in South Africa, and the calculations used in the model. Blue arrows indicate the movement of horse or midge individuals from one compartment to the next, whereas red, dotted lines indicate the transmission of AHSV from host to vector or vector to host. The base layer of the map is publicly available to download from the Municipal Demarcation Board of South Africa (2018) [21].
Fig 2.
Graphs showing the outputs of the model simulation.
Line graphs demonstrating the changes in the horse population when the simulation was run for 360 days varying the start date from January to December (A-L).
Fig 3.
Graphs showing the outputs of the model simulation.
Line graphs demonstrating the changes in the midge vector population when the simulation was run for 360 days varying the start date from January to December (A-L).
Table 1.
Parameters were informed by the re-parameterised AHS model developed by Fairbanks (2022) [14], the Netherlands AHS model by Backer and Nodelijk (2011) [4] and the bluetongue model by Szmaragd et. al. (2009) [36].
Fig 4.
Graph showing the outputs of the model simulation.
Time-series graph demonstrating how the reproduction number (Rv) varied depending on the start month of the simulation.
Fig 5.
Overview of the outbreak dynamics in the AHS control zone from the model simulation.
(A) Spatiotemporal maps showing the number of affected (dead or recovered) horses in the outbreak with varying start months of the simulation from January to December (A-L). (B) Box plots displaying the number of days to the peak infection day depending on the start month of the simulation. (C) Similarly, box plots displaying the length of the outbreak in days depending on the start month of the simulation. The base layer of the map is publicly available to download from the Municipal Demarcation Board of South Africa (2018) [21].
Fig 6.
Maps displaying the locations of the eight known AHS outbreaks in the control area, and the number of affected horses in the simulation, based on the months they originated in.
Months included February (A), March (B) or April (C). The base layer of the map is publicly available to download from the Municipal Demarcation Board of South Africa (2018) [21].
Fig 7.
Graphs showing the relationship between the reproduction number (Rv) and the midge to horse ratio.
Scatterplots for each simulation start month, demonstrating how the midge:horse ratio and Rv vary depending on the AHS control zone.