Survival of African swine fever virus in feed, bedding materials and mechanical vectors and their potential role in virus transmission

Over the last years, African swine fever (ASF) has gone pandemic and within the European Union affected wild boar populations are main drivers. This brings new challenges, i.e. risk assessment needs for agricultural products and the role of mechanical arthropod vectors. Answering the call “Survival of African swine fever virus in feed, bedding materials and mechanical vectors and their potential role in virus transmission” (GP/EFSA/ALPHA/2021/09), relevant feed and bedding materials were chosen for stability experiments. All matrices were contaminated with ASFV and stored at five different ambient conditions (‐20°C, 4°C, 10°C, 20°C, and 37°C) over a period of up to nine months. Replicate samples were evaluated at different time‐points using real‐time PCRs and virus isolation. Additionally, the possible role of three types of blood‐sucking arthropods was assessed. In detail, studies were carried out on how long representative arthropods harbored viral genome and infectious virus upon feeding on infectious blood. In a last step, further proof‐of‐concept data were generated on the transmission of ASFV via ingestion of (small) arthropods after an infected blood meal. Concluding, detection of infectious virus was rather limited in most matrices while detection of viral genome was possible over the entire study period. At lower temperatures, however, the virus was stable on feed matrices over several days or even weeks, especially on beet and potatoes. Grass, grass silage and corn silage did not allow re‐isolation of virus at any time‐point. The studies on the detectability of the virus in arthropods showed that the virus is generally detectable for a certain period of time depending on temperature and ingested volume. The detectability of virus in stable flies exceeded the expectations with over 168 hours at cool temperatures. The feeding experiment did not lead to infection of pigs. However, the power of this proof‐of‐concept study is limited.