Ten years ago, the authors of this article described for the first time in Spain a filovirus that caused the mass death of bats. common bent-winged bat In the Lloviu cave in Asturias.

Now, after the publication of an article, the virus started gaining prominence again. Nature Communication About leading the isolation of the filovirus bats Lloviu in Hungary. He even suggested that in some ways this virus could pose a threat to human health and even be a potential cause of a pandemic.

Are there objective reasons for such fears?

African filoviruses and hemorrhagic fevers

Lloviu is a relative of the Ebola and Marburg viruses that cause hemorrhagic fever in sub-Saharan Africa associated with high mortality. For a long time they only affected isolated rural communities, causing moderate-sized (tens to hundreds of people) epidemics.

Things changed in 2014 after the Ebola virus reached major urban centers, causing an outbreak of tens of thousands of cases. It’s the first time he’s sounded the alarm outside the area. And Ebola is starting to worry us all.

The natural hosts of the Marburg virus are considered to be bats of the species. Rosettus aegyptiacusthose who do not get sick, given their high degree of mutual adaptation. But when the same virus infects other alien species like ours, it causes a very serious, even deadly, disease.

Evidence that bats are reservoirs of Ebola viruses is not so strong. Unlike the Marburg virus, the most pathogenic viral strains in bats have not yet been isolated. Yes, viral nucleic acids and specific antibodies against it have been detected in some bat species. As in the case of the Marburg virus, Ebola-infected bats do not appear to develop disease, but primates, including humans, do.

First European filovirus

Lloviu Filovirus was first described in Spain, 2011, in a mass death event in cave sticks (analysis of archive samples)common bent-winged bat) affected several populations of this species in France, Spain and Portugal in 2002.

The virus was given this name because the people studied came from the Lloviu cave in Asturias. This bat species gathers in large colonies during hibernation, making it particularly vulnerable and can seriously compromise its conservation.

At the time, our lab was already collaborating with bat experts on rabies research. Therefore, given the growing concern, we conducted research to look for viruses in the carcasses of affected bats. However, we found no findings that would allow us to establish a causal relationship with death.

Later, bats began to be associated with some families of viruses pathogenic for humans, such as coronaviruses, henipaviruses or filoviruses. The focus of our common virus studies in bats has gone beyond lyssaviruses and rabies. This is how the Virobat projects, the fourth of which is being completed, started.

In this context, we tracked archival samples from 2002 cave bat deaths and found, then, to our surprise that these bats had significant viral loads of an unknown filovirus in various organs, particularly the lungs. Exactly, the most affected organs according to pathological anatomy studies. Transmission of this filovirus seemed to be the most plausible explanation for the mass death event, in the absence of more robust hypotheses.

The sequence of the detected virus placed it within the Filoviridae family, as did the Ebola and Marburg viruses. We later named it Lloviu virus (LLOV) and it was classified as a new genus (Cuevavirus).

At that time, two unknowns remained open. First, to confirm the pathogenic potential of this virus for bats. The second was to explain why it caused a massive and rapid death. schreibersiisomething that often contrasts with the high degree of mutual adaptation that characterizes the relationship between a virus and its natural host.

Cave bat: just a victim or a natural host?

In a subsequent study, we found antibodies to Lloviu virus in healthy cave bats caught in Asturias and Cantabria in 2015. This meant that viral infection was frequent and did not always lead to death. Something more in line with its role as a natural reservoir.

In the aforementioned study in Hungary, in addition to the antibodies, the authors detected the virus genome in organs taken from the corpses of Hungarian cave bat populations unaffected by mass death. Also in the blood of healthy individuals. Even in ectoparasites collected from the same individuals.

There is no doubt that this virus can infect this bat species without causing illness, and so everything points to it being its natural reservoir.

However, it remains to be seen what makes a virus whose circulation often appears to be compatible with maintaining stable populations appears to be associated with occasional major death events.

Is Lloviu filovirus potentially infectious and pathogenic to humans?

That’s really the million dollar question. Initially, none of the people who came into contact with bat carcasses during the 2002 incident showed symptoms. It was handled in high biological safety conditions during research studies because of its association with everything and with it the Ebola virus.

While describing the presence of antibodies in healthy colonies of cave bats, we failed to look for antibodies to the virus in the sera of 22 individuals with a history of capturing and using this bat species. No human being in contact with bats of this species showed any signs of disease or infection.

Finally, in the new cave study in Hungary, the authors were able to isolate the virus in culture from the blood of infected cave bats using cells from the same bat species. Only in this case, the virus thus obtained in high concentrations has shown that it is able to infect cells of other mammals, including those of human origin.

the fact that the conditions in a laboratory setting It is able to infect cells derived from other mammalian species, including humans, thus remains the only indication of the potential of this virus to infect species other than its natural host.

No reason for social alarm

It is certainly interesting to continue working in this direction. But claiming that this virus has emerged or has pandemic potential is purely speculative and should not be used to alarm the public.

From the facts we have just cited, it is clear that reacting in an alarming way has no objective basis and is extremely harmful. All that has been achieved is to unduly cause unrest and once again present a negative image that could adversely affect bat conservation.

Let’s remember that bats play an important role in the natural control of insect populations, are our best ally in vector control of infectious diseases, and play an important role in reducing the use of harmful pesticides. We are talking about animals that are extremely beneficial to human health. Therefore, it is our obligation to protect them, even if only for our own selfish interests.

Juan E. Echevarría Mayo, scientific researcher at the National Center for Microbiology, Carlos III Institute of Health and Ana Isabel Negredo, senior scientist at the National Center for Microbiology, Carlos III Institute of Health

This article was originally published on The Conversation. Read the original.