Many investigations have looked at animals as possible carriers of the virus and responsible for contagion to humans. But the truth is that scientists are not sure that this is the case.
All the data collected indicates that domestic animals have been, as on other occasions, collateral and anecdotal victims of this pandemic. Dogs, cats and big cats are now joined by minks as animals susceptible to the virus, and that could have infected a farm worker. But a lot of precise data is missing to confirm it.
What is clear is that if we compare the number of animal cases described (11 cats, four dogs, a tiger, a lion and several mink farms) and the number of human cases (more than 5.2 million cases throughout the world), COVID-19 can be considered to be a human disease transmitted primarily between humans.
In fact, control measures against the spread of SARS-CoV-2 aimed exclusively at humans (distancing, confinement, hand washing / disinfection, etc.) are having a decisive impact on the control of this epidemic.
As stated by important institutions in the field of Animal Health, such as the World Organization for Animal Health (OIE), the Centers for Disease Control and Prevention (CDC) or the American Veterinary Medical Association (AVMA), considering the information Currently available, pets do not appear to play a relevant epidemiological role in the spread of COVID-19.
Most of the animal cases of SARS-CoV-2 (detection of viral RNA and / or antibodies against the virus) described to date showed mild or non-existent symptoms, referring to previous contact with people (owners, caretakers, etc.) diagnosed of COVID-19 or with suspected illness as the most likely cause of infection. That is, the direction of transmission of this new coronavirus in the specific cases described in animals has been from humans to animals and not the other way around ... Until three days ago.
Mink, susceptible to SARS-CoV-2
Just over a month ago, we learned that SARS-CoV-2 had been detected in two mink farms in the Netherlands. Two weeks later, two other mink farms affected by COVID-19 were described in this same country. This virus, therefore, had reached a new animal species, causing gastrointestinal symptoms and respiratory symptoms in some individuals, and even dead animals.
The percentage of morbidity and mortality caused by SARS-CoV-2 is low and it seems that the disease especially affects pregnant females. Actually, this news is not that surprising.
Different studies had already shown that ferrets, which are mustelids like minks, are a species highly susceptible to SARS-CoV-2. In fact, ferrets are considered a good animal model to study relevant aspects (pathogenicity, transmissibility, vaccine efficacy, among others) of SARS-CoV-2.
This new case of COVID-19 in a domestic species has revealed very important aspects of this disease: although it is believed that the animals were primarily infected by workers who had previously developed symptoms compatible with COVID-19, it will be investigated if it could have existed a possible transmission between minks.
It has previously been observed that both cats and ferrets can transmit the disease to other conspecifics under very specific experimental conditions, which are usually very different from the natural conditions in which domestic animals live.
In addition, asymptomatic infected minks have been found that may therefore go unnoticed on clinical examination. Eleven cats from the affected farms have also been tested, of which three have been found to be seropositive for COVID-19. This reveals that they have been in contact with the virus and that they may have played a role in the transmission cycle.
First suspected case of contagion from animals to humans
And finally, it is investigated whether an employee of one of the affected farms had contracted SARS-CoV-2 from minks. This possibility, still to be confirmed, is based on a genetic study of virus strains recovered from various animals and humans, but the conclusion of which points to the need to provide more data.
If this were the case, and although it seems like a drastic change in the paradigm that COVID-19 is an essential -but not only- human disease, we would be talking about a specific case in a very unique epidemiological context. Epidemiology requires population data and, therefore, abundant. This case would be just an exception.
In this situation, the Dutch authorities in the matter have implemented a series of measures to guarantee public health, animal health and generate the necessary knowledge that allows knowing the real scope of the particular case of COVID-19 in mink.
We must not fall for alarmist messages that endanger animal welfare, but we must also be aware of (allow us the metaphor) that this puzzle is still missing many pieces. Only when we have a (more) complete picture of the problem can we take control and prevention measures based on evidence, which is the best strategy to fight efficiently against this virus that has changed the course of our history.
This is a new scenario in which, once again, doctors, veterinarians and other health actors must work together and coordinated through the vision ofOne Health,whose concept has come to help, unwittingly, a virus that has shown that we live in a world totally connected for the good ... and for the bad.
Ultimately, it is necessary to investigate, investigate and investigate.
By Marta Pérez-Sancho and Víctor Briones They are researchers in the Department of Animal Health, in the Faculty of Veterinary Medicine and Veterinary Health Surveillance Center (VISAVET), of the Complutense University of Madrid.