DOI: 10.5061/dryad.79cnp5hrv
title: Ecological drivers of African swine fever virus persistence in wild boar populations: insight for control

description: Environmental sources of infection can play a primary role in shaping
 epidemiological dynamics, however the relative impact of environmental
 transmission on host-pathogen systems is rarely estimated. We developed
 and fit a spatially-explicit model of African swine fever virus (ASFV) in
 wild boar to estimate what proportion of carcass-based transmission is
 contributing to the low-level persistence of ASFV in Eastern European wild
 boar. Our model was developed based on ecological insight and data from
 field studies of ASFV and wild boar in Eastern Poland. We predicted that
 carcass-based transmission would play a substantial role in persistence,
 especially in low-density host populations where contact rates are low. By
 fitting the model to outbreak data using Approximate Bayesian Computation,
 we inferred that between 53 to 66% of transmission events were
 carcass-based – i.e., transmitted through contact of a live host with a
 contaminated carcass. Model fitting and sensitivity analyses showed that
 the frequency of carcass-based transmission increased with decreasing host
 density, suggesting that management policies should emphasize the removal
 of carcasses and consider how reductions in host densities may drive
 carcass-based transmission. Sensitivity analyses also demonstrated that
 carcass-based transmission is necessary for the autonomous persistence of
 ASFV under realistic parameters. Autonomous persistence through direct
 transmission alone required high host densities; otherwise re-introduction
 of virus periodically was required for persistence when direct
 transmission probabilities were moderately high. We quantify the relative
 role of different persistence mechanisms for a low-prevalence disease
 using readily collected ecological data and viral surveillance data.
 Understanding how the frequency of different transmission mechanisms vary
 across host densities can help identify optimal management strategies
 across changing ecological conditions.
description: Following the first occurrence of ASF in Poland, an intensive
 surveillance program was implemented in the affected area. The strategy
 was based on laboratory tests of all wild boar found dead and killed in
 road accidents (passive surveillance) and all hunted wild boar (active
 surveillance). A total of 4625 boar were hunted and 271 dead carcasses
 were sampled in Poland during 2014-2015. Samples, collected by veterinary
 services and hunters, were submitted to the National Reference Laboratory
 for ASFV diagnostics at the National Veterinary Research Institute in
 Puławy, Poland. We used surveillance data from 8 administrative districts
 in Poland where ASFV was detected between 2014 and 2015. A detailed
 description of laboratory procedures and tests can be found in
 Woźniakowski et al. 2016. Citation: Woźniakowski, G.,
 Kozak, E., Kowalczyk, A., Łyjak, M., Pomorska-Mól, M., Niemczuk, K.,
 & Pejsak, Z. (2016). Current status of African swine fever virus
 in a population of wild boar in eastern Poland (2014-2015).
 <i>Archives of virology</i>, <i>161</i>(1),
 189-195.