Since the start of the COVID-19 pandemic, animals have been very present in the media. The reason being that they play an essential role in our world, most often this goes unnoticed but in tough times importance of animals becomes more visible.
A few examples, animals have been related to the very origin of the disease, we have seen a huge increase of the demand of animal sourced foods, also there are articles pointin out to the possibility of some of them being carriers of the virus and also we have read about the physical and psychologycal consequences that this lockdown may have on our pets.
First of all, let’s start with the recent news that point out that some animals could carry the virus. All of us have seen that a tiger has tested positive in a zoo in New York.
A recent study released a few days ago in China proves that dogs, pigs and poultry (chicken and ducks) are not infected by the virus. They can carry the pathogen as much as any inanimated object such as a door know or an elevator button, but –and this is very important- the virus does NOT multiply in these species. Conversely, it seems that Covid-19 does multiply and infect cats and ferrets BUT, the doses used in this study are much higher than those at which animals would be exposed in natural conditions.
Another study, released a few days ago in China, describes the impact of the epidemics in 102 cats found in Wuham the very epicenter of the current pandemic once the disease was over,. Of all the 102 cats, 15 tested positive, they had antibodies against the virus. The cats antibody response was quite feeble except for 3 which had been living with people who were positive to Covid-19. This makes the experts think that they got the infection from their owners. The other cats were either stray animals or they did come from shelters, no info is available of the source of their infection but experts believe that people who fed them could have been the origin. Now, this point is really important: although the cats had antibodies, the swabs taken from their throat and rectum didn’t show any presence of the virus.
Fig 1: Level of antibodies in cats pre and post pandemic in Wuham
This absence of viral genetic material can be explained by one of these factors:
- The virus does not replicate enough in cats so that the total amount of viral RNA is too small to be detected
- The time of virus shedding is extremelly short
- Some factor in cat’s DNA doesn’t allow the diagnostic test to perform properly
Again, no virus material was recovered from 102 cats from the very center of the origin of the pandemic. So with this information, we can conclude that it is extremely unlikely that cats transmit the disease between them or to humans.
As for the infected tiger in New York, we know that she had mild symptoms and that her handler tested positive to covid-19. Again, here the animals has been the victim of the infected human.
So, in summary, with the information we have available, all evidence points out to cats being susceptible to the infection, they have mild symptoms but do no shed virus or they do so with a very low load or for a very short time. They would act as a de facto cul-de-sac for the infection.
To reinforce the points above, this is the position of the OIE (World Organization for Animal Health):
The current spread of COVID-19 is a result of human to human transmission. To date, there is no evidence that companion animals have spread the disease. Therefore, there is no justification in taking measures against companion animals which may compromise their welfare.
Some examples of animal infections have been reported to the OIE. Further details on these events can be found in the ‘more information’ section. So far, these appear to be isolated cases, and there is no evidence that dogs or cats are playing a role in the spread of this human disease. Further studies are underway to understand if and how different animals could be affected by COVID-19 virus.
Fig 2: Domestic animals do not infect humans
It is good news that animals cannot infect us, but also it’s very important to note that we cannot infect farm animals. It may seem not relevant but it is essential because if we could infect farm animals, all the food chain would be at risk as livestock is often in contact with their handlers, vets, etc. This would make animal sourced products less available. Fortunately, this is not the case and as this pandemic has proven the need for eggs, milk and meat has increased significantly and this increase has proven how relevant animal products are in our nutrition and how, in difficult times, we resort to them and store significant amounts of what we consider really important.
Fig 3 & 4: On the left increase of demand of different types of meat in the US at the start of the pandemic. On the right, evolution of eggs price
But there are other aspects in which animals help us at these times of lockdown. Pets are with us, their companionship is now probably more valuable than ever. But confinement is not easy for them. As we are all day long at home, our pets could become used to this situation. Once it changes, and we leave home for work, some of our friends may develop some anxiety. In order to avoid it, some experts advise to leave the dog alone in a room for some hours every day,during the lockdown with this they will get used to be on their own and accept to be alone once our lives go back to normal.
Fig 5: Lockdown is not only difficult for people
It is also important to keep the times and routines of our friends as untouched as posible: meals, walking times. This provides our dog or cat with some structure. They can adopt very quickly new habits –especially those they like as being with us long hours- but we must be aware that this is going to change and get ready for that moment, when it comes.
Long hours at home, specially in small appartments, could be tough for pets too. A good practice would be to stimulate them mentally. As an example, you can hide a treat into a box and mix the box with many others. Games like this could be entertaining for everybody and keep your pet motivated and active.
Fig 6: Anxiety in a dog
Besides, it is important to keep our friend in good health: have his/her food available, medicines and be virtually connected with our vet.
Another important point, in case you live on your own with your pet, is to plan with whom we will leave it in case we fall sick. It is our responsibility to plan for it.
There’s been a lot of scientific bibliography published on the origin of the virus that causes Covid-19. Bats and pangolins have been considered by some as the most likely sources of the pandemic. However, as of today, this has not been proven. This is what the OIE says about this particular:
The predominant route of transmission of COVID-19 is from human to human.
Current evidence suggests that the COVID-19 virus emerged from an animal source. Investigations are underway to find that source (including species involved) and establish the potential role of an animal reservoir in this disease. However, to date, there is not enough scientific evidence to identify the source or to explain the original route of transmission from an animal source to humans.
Genetic sequence data reveals that the COVID-19 virus is a close relative of other CoV found circulating in Rhinolophus bat (Horseshoe Bat) populations. There is the possibility that transmission to humans involved an intermediate host.
So, it is likely that the virus comes from animal species, but this has not yet been 100% proven.
Fig 7: Pangolins and bats could be at the very origin of the pandemic.
One more contribution of pets to control Covid-19 is brought by dogs who are trained to smell the disease. With the right training, dogs can detect metabolites in infected people that can be used as a diagnostic. Actually, the Medical Detection Dog, an organization specialized on these trainings, does exactly this, prepare dogs to detect positives in samples taken from people suffering from different conditions.
Covid will pass and whatever the final solution is, either a vaccine or a drug, it will be brought to us thanks to trials conducted on animals. Our society depend on them in many, many aspects. I hope this article has been useful to make their contribution a little better known.
- Shi, J. et al.Preprint at bioRxiv https://doi.org/10.1101/2020.03.30.015347 (2020)