The scientific community frequently encounters new viruses, and understanding these emerging pathogens is a continuous endeavor. The Lloviu virus (LLOV) represents one such recently identified agent, drawing attention due to its unique characteristics.
Discovery and Classification
The Lloviu virus was initially discovered in 2011 from samples collected in 2002 from dead Schreiber’s long-fingered bats (Miniopterus schreibersii) in Cueva del Lloviu, Asturias, Spain. The virus was subsequently identified in Hungary in 2016 from bat die-off events.
LLOV is classified within the Filoviridae family, a group of negative-sense RNA viruses known for their filamentous shape. This family also includes the more widely recognized Ebola virus and Marburg virus. Despite its relation to these highly pathogenic viruses, LLOV is distinct enough genetically to be classified within its own genus, Cuevavirus, which was proposed in 2010 and formally ratified in 2013 by the International Committee on Taxonomy of Viruses (ICTV).
The genetic organization of LLOV is similar to that of Ebolaviruses, including the encoding of specific proteins like VP24, VP40, and GP1,2, with GP1,2 production relying on RNA editing. This genomic architecture provides insights into its replication strategies within host cells. Understanding its place within the Filoviridae family and its unique genetic makeup allows scientists to better understand the broader evolutionary relationships among these viruses.
Natural Hosts and Geographic Distribution
The primary natural host for the Lloviu virus is the common bent-wing bat, Miniopterus schreibersii. LLOV RNA has been detected in both deceased and live bats of this species, and infectious virus has been isolated from them, confirming it as a natural reservoir in Europe.
The virus was first detected in Spain, specifically in the Cueva del Lloviu in Asturias, and later in Cantabria, France, and Portugal. Subsequent detections in Hungary in 2016 and more recently in Bosnia and Herzegovina confirm a wider geographic distribution across Europe. This suggests the virus circulates among Miniopterus schreibersii colonies across a significant portion of the continent.
Bats are recognized reservoirs for numerous viruses, many of which have the potential to spread to other species. The presence of LLOV in Miniopterus schreibersii is consistent with the role of bats in viral ecology, where they can host viruses without showing severe disease, potentially facilitating their spread. It has also been observed that LLOV RNA can be found in ectoparasites, such as bat flies and ticks, found on these bats, raising questions about their potential role in viral ecology.
Potential Human Health Implications
Currently, there is no direct evidence that Lloviu virus has caused disease in humans. Despite the Cueva del Lloviu, where the virus was first found, being frequented by tourists, no human infections or associated illnesses have been observed. However, the potential for zoonotic spillover, the transmission of a virus from animals to humans, remains a subject of ongoing investigation.
Research indicates that LLOV is capable of infecting human cells in laboratory settings, including primary human macrophages, hepatocytes, and lung cells, which are common targets for other pathogenic filoviruses. This ability to infect human cells suggests that spillover to humans might be biologically possible. However, studies also suggest that LLOV infection in human macrophages may not induce a strong inflammatory response, which is a characteristic feature of severe Ebola virus disease.
The pathogenicity of filoviruses varies considerably; for example, Reston virus, another filovirus, is not known to cause disease in humans. Public health surveillance efforts are therefore important, particularly given LLOV’s genetic relationship to highly pathogenic viruses like Ebola and Marburg viruses. Understanding factors that contribute to zoonotic spillover events, such as human-animal interactions and bat population dynamics, is also a focus of research.
Ongoing Research and Surveillance
Scientists are actively researching the Lloviu virus to understand its biological properties, including its replication mechanisms and potential for cross-species infection. Advances in molecular virology, such as the development of recombinant LLOV systems, have allowed researchers to study the virus more effectively, even when complete genome sequences were initially unavailable. These systems help in identifying the genetic elements necessary for the virus to replicate.
Ongoing surveillance programs are monitoring LLOV in bat populations, particularly in Miniopterus schreibersii, to track its presence and observe any changes in its genetic makeup or prevalence. These studies involve detecting viral RNA in bat samples and assessing seropositivity, indicating past exposure to the virus. The detection of LLOV in bat ectoparasites also suggests new avenues for indirect surveillance.
Global collaboration among scientists is important for tracking emerging viruses like LLOV. This includes sharing genetic data and research findings to better understand viral evolution and geographical spread. Continued research into LLOV’s specific risk to humans and its potential for causing disease will inform public health preparedness strategies for any future zoonotic events.