A scoping review of African swine fever virus spread between domestic
and free-living pigs
Abstract
Since 2007, African swine fever virus (ASFV) has spread to countries in
Europe, Asia and Oceania, and has caused devastating impacts on pigs and
the pork industry. Transmission can be direct or indirect, and
epidemiologic scenarios have been described in which spread occurs
between free-living and domestic pigs. The purpose of this scoping
review was to identify primary research in which authors made statements
to support ASFV transmission between free-living and domestic pigs and
assess the circumstances in which transmission events occurred. A search
was conducted in five bibliographic databases and the grey literature.
Two reviewers (from a team of ten) independently screened each record
and charted data (demographics of the pig populations, their husbandry
[domestic pigs] and habitat [free-living pigs], the spatial and
temporal distribution of ASF, the occurrence or burden of ASF in the
populations, and whether ticks were present in the geographic range of
the pig populations). Data synthesis included statistics and a narrative
summary. From 1,349 records screened, data were charted from 46
individual studies published from 1985 to 2020. Outbreak investigations
revealed that whilst poor biosecurity of domestic pig operations was
often reported, direct contact resulting in transmission between
free-living and domestic pigs was rarely reported. Studies in which
quantitative associations were made generally found that spread within
populations was more important than spread between populations, although
this was not always the case, particularly when domestic pigs were
free-ranging. We conclude that there is limited evidence that
transmission of ASFV between free-living and domestic pigs is an
important feature of ASF epidemiology, especially in the current ASF
epidemic in Europe and the Russian Federation. If ASFV elimination
cannot be achieved in free-living pigs, compartmentalisation of
free-living and domestic pig populations via biosecurity strategies
could be used to support trade of domestic pigs.