Stability of African swine fever virus in soil and options to mitigate
the potential transmission risk
Abstract
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.