A new study conducted by the scientists at the Friedrich Loeffler Institute, Germany, noted that raccoon dogs were a potential intermediate host in the transmission of the coronavirus.

The paper’s preprint version was published on the bioRxiv .

The study revealed that animals that were intranasally inoculated with SARS-CoV-2 quickly became infected and went on to transmit the virus to other direct-contact animals.

Thomas Mettenleiter, the lead author of the study, and his colleagues stated in their research: “With China’s substantial contribution to the global fur production of over 50 million animals per annum, it is conceivable that raccoon dogs may have played a hitherto unexplored role in the development of the pandemic.”

The findings supported the implementation of adequate surveillance and risk mitigation strategies for both farmed and wild raccoon dogs, the authors added.

Scientists speculated that Covid-19 has been transmitted through bats. However, whether the virus got directly transmitted to humans or not still remains unclear.

“Increasing evidence supports the potential of several carnivore species to become infected by SARS-CoV-2 as a result of anthropo-zoonotic transmission, possibly leading to re-infections of humans,” said Mettenleiter and team.

Natural SARS-CoV-1 infection of raccoon dogs has been documented, suggesting the animals’ potential involvement in the 2002-2003 SARS outbreak. While some studies revealed that in raccoon dogs, the host cell protein angiotensin-converting enzyme-2 (ACE2) serves as an efficient receptor of both SARS and Covid-19.

Virus transmission

Mettenleiter and his team tested susceptibility to SARS-CoV-2 in raccoon dogs by infecting nine animals with the virus. They then examined transmission by introducing three further animals 24 hours post-infection.

The study found that six of the original nine animals became infected with SARS-CoV-2. The animals had already started to shed viral RNA in nasal and oropharyngeal swabs at two days post-infection, and the infectious virus was isolated from individual animals up to four days post-infection.

Viral RNA was present in the nasal swabs up to 16 days following infection, with the highest viral genome loads found in nasal swabs, followed by oropharyngeal swabs and then rectal swabs.

The virus was transmitted to two of the three contact raccoon dogs that were introduced; one dog tested negative due to its cage neighbours not shedding the virus following infection.

None of the animals exhibited any apparent signs of infection, and at autopsy, no gross lesions that could be attributed to SARS-CoV-2 were observed.

“Except for mild rhinitis associated with the presence of viral antigen in the nasal mucosa, no other infection-related histopathological changes were observed,” said the team.

“Our results support the establishment of adequate surveillance and risk mitigation strategies for kept and wild raccoon dogs.,” concluded the team.