Evidence of aerosol transmission of African swine fever virus between two piggeries under field conditions: a case study

Abstract

African swine fever (ASF) is a devastating and economically significant infectious disease that has caused enormous losses in the commercial pig sector in China since 2018. The primary transmission routes of the African swine fever virus (ASFV), the causative agent of ASF, are direct pig-to-pig contact or indirect contact with virus-contaminated objects. While aerosol transmission of ASFV has been previously reported under experimental conditions, no reports have described it under field conditions. In this case study, aerosol-associated samples were collected over a monitoring period of 24 days in an ASFV-positive farm. A complete and clear chain of ASFV transmission through aerosols was observed: pigs in Room A on Day 0-aerosol in Room A on Day 6-dust of air outlets in Room A on Day 9-outdoor aerosols on Day 9-dust of air inlets in Room B on Day 15-aerosols/pigs in Room B on Day 21. Furthermore, a fluorescent powder experiment confirmed the transmission of dust from Room A to Room B. This study represents the first report providing evidence of aerosol transmission of ASFV under field conditions. Further research is needed to study the laws of aerosol transmission in ASFV and develop effective strategies such as air filtration or disinfection to create a low-risk environment with fresh air for pig herds.

Resumption of production operations during the silent disposal period of African swine fever outbreaks: a case study

“…Furthermore, the disinfection and inactivation of the virus in the environment are deemed equally crucial aspects to consider. The aerosol transmission of ASF has also gained attention among farmers [ 15 , 16 ]. Consequently, it is imperative to consider future measures aimed at eradicating the virus present in aerosols.…”

A suitable sampling strategy for the detection of African swine fever virus in living and deceased pigs in the field: a retrospective study

“…Moreover, the duration required for virus detection in the bloodstream varies depending on the various modes of infection, with contact transmission exhibiting a delay of 1–2 days compared to intramuscular injection ( 8 , 11 , 12 ). Additionally, ASFV has been reported to be able to spread through multiple routes, including contact and aerosol transmission ( 11 , 13 , 14 ). And also, ASFV-positive pigs have been found to harbor a significant quantity of virus particles in their blood and deep tissues ( 10 , 11 , 15–17 ), which indicates that the process of blood sampling and necropsy procedures may lead to extensive contamination of the virus within the facility in the event of ASFV outbreaks in large-scale farms.…”

Airborne transmission of common swine viruses

“…European ASFV strains were also shown to spread through aerosols among pigs through aerosols, infecting healthy pigs in separate pens [ 77 ]. According to the latest research by Li et al, the transmission distance of ASFV Asian strains under field conditions can reach up to 10 m [ 78 ]. And secretions carrying high viral titers from ASFV-positive pigs during sneezing and coughing can be aerosolized and emitted into the environment [ 79 , 80 ].…”

“…Extensive research has been conducted on the utilization of mathematical models in the context of FMDV [ 14 – 16 ], and this approach can be further applied to the investigation of other virus aerosols. Moreover, recent comprehensive case reports and source tracing analyses pertaining to the aerosol transmission of ASFV [ 78 ] and COVID-19 [ 108 ] have yielded exemplary demonstrations. Consequently, more case reports on the aerosol transmission of viruses should be encouraged in the future.…”

“…Given the escalating threat of ASFV to pig production, numerous detection methods for swine viruses with high sensitivity have been devised, such as digital polymerase chain reaction (dPCR) [ 112 ], insulated Isothermal PCR (iiPCR) [ 113 ], offering promising prospects for detection of viral aerosols. As for air sampling devices, Li et al used two different air samplers with different flow rates to collect aerosols within and between barns respectively, demonstrating the aerosol transmission of ASFV under field conditions [ 78 ]. In a separate study, Lee et al developed a portable integrated bioaerosol sampling/ monitoring platform that can detect viral aerosol particles within 20 min using the signal of near-infrared (NIR)-to-NIR nanoprobes [ 114 ].…”