Infectious droplet exposure is an inefficient route for SARS-CoV-2 infection in the ferret model

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19) in humans, has a wide host range, naturally infecting felids, canids, cervids, rodents and mustelids. Transmission of SARS-CoV-2 is universally accepted to occur via contact with contaminated secretions from the respiratory epithelium, either directly or indirectly. Transmission via droplet nuclei, generated from a cough or sneeze, has also been reported in several human and experimental animal scenarios. However, the role of droplet transmission at the human–animal interface remains to be fully elucidated. Here, the ferret infection model was used to investigate the routes of infection for the SARS-CoV-2 beta variant (B.1.351). Ferrets were exposed to droplets containing infectious SARS-CoV-2, ranging between 4 and 106 µm in diameter, simulating larger droplets produced by a cough from an infected person. Following exposure, viral RNA was detected on the fur of ferrets, and was deposited onto environmental surfaces, as well as the fur of ferrets placed in direct contact; SARS-CoV-2 remained infectious on the fur for at least 48 h. Low levels of viral RNA were detected in the nasal washes early post-exposure, yet none of the directly exposed, or direct-contact ferrets, became robustly infected or seroconverted to SARS-CoV-2. In comparison, ferrets intranasally inoculated with the SARS-CoV-2 beta variant became robustly infected, shedding viral RNA and infectious virus from the nasal cavity, with transmission to 75 % of naive ferrets placed in direct contact. These data suggest that larger infectious droplet nuclei and contaminated fur play minor roles in SARS-CoV-2 transmission among mustelids and potentially other companion animals.

Clade 2.3.4.4b H5N1 high pathogenicity avian influenza virus (HPAIV) from the 2021/22 epizootic is highly duck adapted and poorly adapted to chickens

“…A novel aspect of the study was to include air sampling in all the H5N1-21 in vivo experiments to assess potential transmission due to microscopic particles which include biological droplets, aerosols or airborne fomites (such as inhalable dust). These particles may harbour infectious virus, with aerosols typically being less than 5 µm in diameter [49][50][51]. In a field environment, infectious H5N8 20/21 has been detected in the air sampled on infected commercial poultry premises, with larger particle sizes (such as inhalable dust) harbouring higher titres of virus [52].…”

Clade 2.3.4.4b H5N1 high pathogenicity avian influenza virus (HPAIV) from the 2021/22 epizootic is highly duck adapted and poorly adapted to chickens

“…A novel aspect of the study was to include air sampling in all the H5N1-21 in vivo experiments to assess potential transmission due to microscopic particles which include biological droplets, aerosols or airborne fomites (such as inhalable dust). These particles may harbour infectious virus, with aerosols typically being less than 5 µm in diameter [50][51][52]. In a field environment, infectious H5N8 20/21 has been detected in the air sampled on infected commercial poultry premises, with larger particle sizes (such as inhalable dust) harbouring higher titres of virus [53].…”

Detection of SARS-CoV-2 Delta Variant (B.1.617.2) in Domestic Dogs and Zoo Tigers in England and Jersey during 2021

“…Virus isolation was attempted for SARS-CoV-2 positive clinical samples identified by RRT-PCR. Clinical material suspended in DMEM or PBS was added to a flask of confluent Vero/hSLAM cells [ 37 ] supplemented with 2% heat inactivated FCS with 1% ( v / v ) Penicillin, Streptomycin, and Nystatin. The cells were incubated for a maximum of seven days at 37 °C with 5% CO 2 and visualised daily for CPE using a microscope.…”