I’m going to have to go back to the start soon and update previous reviews of COVID-19 in animals, but there are still a couple of more species worth mentioning first. Cattle are an obvious consideration because they are important food animals that are widely raised in countries around the world, and they are often housed in large groups. Some cattle, especially dairy cattle, have a lot of contact with people. More human contact means more risk of exposure to the SARS-CoV-2 virus, and more animals in a group means more risk of animal-to-animal spread (and possibly mutation of the virus, as has recently been seen in mink in Denmark).
Fortunately, the SARS-CoV-2 virus doesn’t seem to like cattle. We probably can’t say they’re not susceptible at all, but based on what we currently know we can say they’re minimally susceptible at most. In terms of spread of SARS-CoV-2, the risk to cattle is minimal, and the risk to people from cattle is pretty much zero.
There was some interest in determining if cattle were susceptible at the start of the pandemic, because cattle are susceptible to bovine coronavirus, which is also a beta-coronavirus, just like SARS-CoV-2. However, cattle were predicted to be low-risk for infection based on the form of their ace2 receptor, the site the virus uses to attach to and subsequently infect cells. Predictions from these receptor-based studies haven’t always been accurate, but they seem to be true in this case. One experimental study in cattle has been reported so far (Ulrich et al.), and it supports the notion that cattle are pretty resistant to infection with SARS-CoV-2. The researchers found that viral RNA was transiently detected at low levels (likely not enough to be infectious) from nasal swabs of 2/6 inoculated cattle, and those two animals developed a very low level of antibodies as well. No cattle that were co-housed with the inoculated cattle became infected. In summary, there was some degree of infection that stimulated the immune system to respond in two animals, but it was a minimal response.
As usual, the two important questions are:
1) Can cattle get sick from SARS-CoV-2?
- We have a single study of 6 cattle of one type and age, which is far from definitive, but it doesn’t indicate any health risk to cattle.
2) Can infected cattle shed the SARS-CoV-2 virus? (and therefore pose a risk to other animals, including humans)
- Virus shedding in cattle doesn’t appear to be a concern. Even if the odd cow can be transiently and mildly infected, it’s very unlikely they would shed enough virus to pass it along to another animal or person.
So, let’s not ignore cattle completely, and let’s still try to keep infected people away from them, but we can probably relax when it comes to SARS-CoV-2 and this particluar species.