Another experimental study of the infectivity of SARS-CoV-2 (the virus that causes COVID-19) in several animal species has provided information largely corroborating results of a similar study of SARS-CoV-2 infectivity released last week. Eventually it becomes unnecessary to duplicate studies like this, but at the start of something new like this, repeated study and independent confirmation are important.
Pigs and chickens
These species were not susceptible to infection. This was the best news in the report, and was consistent with the previous study from China. There have been theoretical concerns about pigs, but while it’s still not definitive, having two negative experimental infection studies suggests that this virus isn’t able to effectively infect pigs.
The species of bat used in this study (the Egyptian fruit bat, Rousettus aegypticus) is quite distantly related to the Chinese horseshoe bat (currently the prime suspect species with regard to the origin of the COVID-19 virus). However, these fruit bats can be bred in captivity and have been used in the past as an experimental animal model, and were likely therefore the most readily available for this study. It’s also useful to look at infectivity in other bat species in terms of learning about whether the virus could potentially be transmitted from people or animals back into other wild bat populations. The Egyptian fruit bat appeared to be somewhat susceptible to the virus: Transient respiratory tract infection occurred, and infectious virus was detected in the nose and trachea in 1 of the 9 bats. More study of bats is probably needed to figure out how relevant these findings are in the bigger picture.
Unsurprisingly, ferrets were the most susceptible species. High levels of virus were detected in 8 of 9 infected ferrets, between 2 and 8 days after infection. Three un-inoculated ferrets were placed in contact with the infected ones, and they all became infected, showing again that ferrets are able to pass on the virus to others.
So, there was nothing particularly surprising in the results, but it’s important to learn more about (and confirm) the host range of the virus for control purposes, for risk assessments (where it might be, where it might go), to understand risks from future related viruses, and to support lab studies such as vaccine or treatment trials.