Infectious potential and circulation of SARS-CoV-2 in wild rats

Area of Science:

• Veterinary Virology
• Zoonotic Disease Research
• Comparative Pathology

Background:

• Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected various animal species.
• Emerging SARS-CoV-2 variants show increased ability to infect previously unsusceptible species, including rodents.

Purpose of the Study:

• To investigate the potential role of urban rats (Rattus norvegicus) in SARS-CoV-2 transmission.
• To assess the susceptibility of rats to SARS-CoV-2 Omicron BA.5 infection.

Main Methods:

• Surveillance of wild rat populations in French urban areas for SARS-CoV-2 antibodies and RNA.
• Experimental inoculation of wild-type and laboratory rats (Rattus norvegicus, Rattus rattus, Sprague-Dawley, Wistar) with SARS-CoV-2 Omicron BA.5.
• In silico analysis of viral receptor binding domain (RBD) affinities to rat ACE2.

Main Results:

• No SARS-CoV-2 antibodies or viral RNA were detected in 401 wild rats surveyed in France.
• Experimental Omicron BA.5 inoculation resulted in low-level viral RNA detection in the upper respiratory tract but no infectious viral particles in lungs or URT.
• Seroconversion was observed in experimentally inoculated rats, but in silico analysis showed lower binding affinity of Omicron BA.5 RBD to rat ACE2 compared to human ACE2.

Conclusions:

• SARS-CoV-2 Omicron BA.5 is unable to establish significant infection in laboratory and wild-type rats.
• Urban rats do not appear to play a significant role in SARS-CoV-2 transmission based on current findings.