Simulation of Spread of African Swine Fever, Including the Effects of Residues from Dead Animals

Abstract

To study the spread of African swine fever (ASF) within a pig unit and the impact of unit size on ASF spread, a simulation model was created. In the model, an animal can be in one of the following stages: susceptible, latent, subclinical, clinical, or recovered. Animals can be infectious during the subclinical stage and are fully infectious during the clinical stage. ASF virus (ASFV) infection through residues of dead animals in the slurries was also modeled in an exponentially fading-out pattern. Low and high transmission rates for ASFV were tested in the model. Robustness analysis was carried out in order to study the impact of uncertain parameters on model predictions. The results showed that the disease may fade out within the pig unit without a major outbreak. Furthermore, they showed that spread of ASFV is dependent on the infectiousness of subclinical animals and the residues of dead animals, the transmission rate of the virus, and importantly the unit size. Moreover, increasing the duration of the latent or the subclinical stages resulted in longer time to disease fade out. The proposed model is a simple and robust tool simulating the spread of ASFV within a pig house taking into account dynamics of ASFV spread and the unit size. The tool can be implemented in simulation models of ASFV spread between herds.

Inferring within-herd transmission parameters for African swine fever virus using mortality data from outbreaks in the Russian Federation

“…In those studies which have estimated parameters, data from both transmission experiments (de Carvalho Ferreira, Backer, et al., ; Guinat, Gubbins, et al., ; Hu et al., ; Nielsen, Karsen, Halasa, & Christiansen, ; Pietschamnn et al., ) and field data (Gulenkin et al., ; Korennoy, Gulenkin, Gogin, Vergne, & Karaulov, ) have been used. This relative paucity of data is reflected in the ASFV modelling literature, where the models (see, e.g., Barongo, Bishop, Fèvre, Knobel, & Ssematimba, ; Halasa, Boklund, Bøtner, Toft, & Thulke, ; Mur et al., ) typically rely on parameters derived from three studies (Gulenkin et al., ; de Carvalho Ferreira, Backer, et al., ; de Carvalho Ferreira, Weesendorp, Quak, Stegeman, & Loeffen, ; Guinat, Gubbins, et al., ).…”

Short time window for transmissibility of African swine fever virus from a contaminated environment

“…Data on the infectivity of animal residues are important when modelling ASFV transmission and the effect of control strategies (Halasa, Boklund, Bøtner, Toft, & Thulke, ). From this perspective, further experimental studies in pigs aimed at investigating the transmission of ASFV from the environment are warranted, as more data are needed to draw conclusions on the effect of environmental contamination in ASFV transmission under field conditions both within domestic pigs and wild boar.…”

Transmission of African swine fever virus from infected pigs by direct contact and aerosol routes

“…The continued circulation of the virus in Eastern Europe means that there is a risk of further spread of ASFV into Western Europe. In European countries, with a large swine production and substantial exports of swine products, it is predicted that ASF outbreaks will have huge economic consequences, especially due to export restrictions (Halasa et al, 2016a;Halasa et al, 2016b). Hence, enforcement of current ASF contingency plans to achieve early detection and eradication of the disease in these countries is of major importance in order to limit these costs (Halasa et al, 2016c).…”