Despite their name, Raccoon Dogs are neither dogs nor raccoons, but are most closely related to the fox. Nocturnal animals, they are native to east Asia, and they - along with the gray fox - are the only canids known to climb trees.
In China, they are raised (and killed) by the millions on `fur farms', raising the ire of animal rights activists around the world.
Last August they were suggested as a potential intermediate host for both SARS-1 and SARS-CoV-2 by researchers at the Friedrich-Loeffler-Institut in Germany (see BioRxiv preprint) after they experimentally infected 9 raccoon dogs with SARS-CoV-2.
That preprint article has now been published in the CDC's EID journal as an early release dispatch. I've only included some excerpts from a much longer report, so follow the link to read it in its entirety.
Volume 26, Number 12—December 2020
Conrad M. Freuling1Comments to Author , Angele Breithaupt1, Thomas Müller, Julia Sehl, Anne Balkema-Buschmann, Melanie Rissmann, Antonia Klein, Claudia Wylezich, Dirk Höper, Kerstin Wernike, Andrea Aebischer, Donata Hoffmann, Virginia Friedrichs, Anca Dorhoi, Martin H. Groschup, Martin Beer, and Thomas C. Mettenleiter
Author affiliation: Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany
Raccoon dogs might have been intermediate hosts for severe acute respiratory syndrome–associated coronavirus in 2002–2004. We demonstrated susceptibility of raccoon dogs to severe acute respiratory syndrome coronavirus 2 infection and transmission to in-contact animals. Infected animals had no signs of illness. Virus replication and tissue lesions occurred in the nasal conchae.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan, China, at the end of 2019. Researchers have identified close relatives to SARS-CoV-2 in bats (1) and pangolins (order Pholidota) (2,3). Whether the pandemic was initiated by direct transmission from bats or through an intermediate mammalian host is still under debate (4). During the 2002–2004 severe acute respiratory syndrome pandemic, researchers documented the causative virus in raccoon dogs (Nyctereutes procyonoides) in China, indicating that these animals might have been intermediate hosts for the virus (5). Fur producers in China own >14 million captive raccoon dogs, accounting for »99% of the global share of raccoon dogs (6) (Appendix Figure 1). However, whether these animals are susceptible to SARS-CoV-2 is unknown. Using our established study design (7), we characterized susceptibility, viral shedding, transmission potential, serologic reactions, and pathologic lesions of raccoon dogs after experimental SARS-CoV-2 infection.
Our experimental study demonstrates that raccoon dogs are susceptible to SARS-CoV-2 infection and can transmit the virus to direct in-contact animals. In our study, raccoon dogs had only subtle clinical signs. We found evidence of viral replication and tissue lesions in only the nasal conchae.
Increasing evidence supports the potential of carnivore species, including farmed fur animals, to become infected by SARS-CoV-2 (8–12). This transmission could eventually cause zoonotic infections in humans (B.B. Oude Munnink, unpub. data: Https://www.biorxiv.org/content/10.1101/2020.09.01.277152v1).
Our results indicate that affected farms might be reservoirs for SARS-CoV-2. Thus, efficient and continuous surveillance should target susceptible animals, including raccoon dogs, especially in China, which is a key player in global fur production (6). We also need to initiate large-scale epidemiologic field studies with historic samples that might elucidate the role of farmed animals in the current pandemic.
Raccoon dogs aren't the only potential intermediate host for COVID-19, as we've seen the mink industry in the Netherlands devastated by SARS-COV-2, and even some signs that humans may have been infected through exposure to infected mink (see COVID-19 detected on multiple Dutch mink farms.
Other nations, including Spain and the United States, have reported outbreaks in mink as well (see USDA APHIS Confirms SARS-CoV-2 in Farmed Mink in Utah).
Mink are also susceptible to both seasonal, and novel influenza (see Vet. MicroB.: Eurasian Avian-Like Swine Influenza A (H1N1) Virus from Mink in China).
Dogs and cats are also plausible intermediate hosts for influenza and SARS-CoV-2 (see J. Clin. Microb: Serological Screening Of Dogs & Cats For Influenza A - Europe and Seroprevalence of SARS-CoV-2 in Dogs & Cats - Italy), although there is currently no evidence to suggest that either play a significant role in spreading COVID-19 to people.
It is possible, of course, that SARS-CoV-2 jumped directly from bats to humans, but the experience with both SARS and MERS is that intermediate hosts are often involved.
Finding, understanding, and hopefully eliminating that reservoir might help prevent the emergence of a SARS-CoV-3 virus someday in the future.