Abstract:
African swine fever (ASF) has been reported in South Africa since the early 20th century.
The disease has been controlled and confined to northern South Africa over the past 80 years
by means of a well-defined boundary line, with strict control measures and movement
restrictions north of this line. In 2012, the first outbreak of ASF outside the ASF control zone
since 1996 occurred. The objective of this study was to evaluate the current relevance of the
ASF control line as a demarcation line between endemic ASF (north) areas and ASF-free
(south) area and to determine whether there was a need to realign its trajectory, given the
recent outbreaks of ASF, global climate changes and urban development since the line’s
inception. A study of ASF determinants was conducted in an area 20 km north and 20 km
south of the ASF control line, in Limpopo, Mpumalanga, North West and Gauteng provinces
between May 2008 and September 2012. The study confirmed that warthogs, warthog
burrows and the soft tick reservoir, Ornithodoros moubata, are present south of the ASF
control line, but no virus or viral DNA was detected in these ticks. There appears to be an
increasing trend in the diurnal maximum temperature and a decrease in humidity along the
line, but the impact of these changes is uncertain. No discernible changes in minimum
temperatures and average rainfall along the disease control line were observed between
1992 and 2014. Even though the reservoirs were found south of the ASF boundary line, the
study concluded that there was no need to realign the trajectory of the ASF disease control
line, with the exception of Limpopo Province. However, the provincial surveillance
programmes for the reservoir, vector and ASF virus south of this line needs to be maintained
and intensified as changing farming practices may favour the spread of ASF virus beyond
the control line.
