Summary
Understanding African swine fever virus (ASFV) transmission in a
population is essential for strategies to minimize virus spread during
an outbreak. ASFV can survive for extended periods of time in animal
products, carcasses, and the environment. Recent studies have shown that
wild boar demonstrate interest in carcasses at an advanced stage of
decay and in the soil where the remains of wild boar once were. While
ASFV nucleic acids have been found in the environment around infected
farms, data on the survival of the virus in soil are scarce. We
investigated different soil matrices spiked with ASFV-positive blood
from infected wild boar to see if ASFV can remain viable in the soil
beneath infected carcasses. Moreover, we tried different mitigation
strategies that could be used in affected regions.
As expected, ASFV genome detection was reliably possible over the full
range of sampling days. Soil pH, structure, and ambient temperature
played a significant role for the stability of infectious ASFV.
Infectious ASFV was demonstrated in specimens originating from sterile
sand for at least three weeks, and from ordinary beach sand for up to
two weeks. In yard soil, infectious ASFV was demonstrated for one week,
and in soil from a swampy area for three days. Virus was not recovered
from two acidic forest soils. All risk mitigation experiments with
citric acid or calcium hydroxide resulted in complete inactivation in
our experimental setup. In conclusion, stability of infectious ASFV is
almost non-existent in forest soils but rather high in sandy soils.
However, given the high variability, treatment of carcass collection
points with disinfectants should be considered for additional risk
reduction. In this respect, biocidal nature and occupational safety have
to be considered.
Keywords : African swine fever virus, stability, soil,
disinfection, risk mitigation