VIRUS LONG CONSIDERED INSECT-SPECIFIC IDENTIFIED IN HORSES

For the first time, a virus previously known only to infect insects has been identified in the tissues of two horses that died as a result of a severe respiratory syndrome. The virus, Alphamesonivirus-1, belongs to the Mesoniviridae family, until now considered exclusive to mosquitoes and other arthropods. The discovery, published in the Journal of Virology, is the result of a joint study conducted by the Istituto Zooprofilattico Sperimentale dell’Abruzzo e del Molise “G. Caporale” in collaboration with international research institutes. A study that opens new hypotheses on the ability of these viruses to cross the species barrier.

“We detected the virus – explains Maurilia Marcacci, Genomics – in the lungs and lymph nodes of a mare and her foal, both of which had died suddenly due to an acute respiratory syndrome. Thanks to genome sequencing techniques, we were able to identify Alphamesonivirus-1, never before found in a mammal.”

The two horses, kept on the same farm in Molise, showed compatible symptoms and lesions, while conventional diagnostic investigations ruled out the main infections known in horses, such as equine influenza and herpesvirus. Only through advanced metagenomic analysis was it possible to identify the presence of the Alphamesonivirus-1 in the tissue samples.

A key element of the discovery is the genetic similarity between the virus detected in the horses and the one isolated from mosquitoes of the genus Culex (the common “house mosquitoes”) captured in the nearby Abruzzo region. This suggests a possible local circulation of the virus between insects and vertebrates. “Our observations – adds Alessandra Spina, Virology – suggest that the virus may not be limited to insects, as previously believed. We cannot yet say whether it caused the death of the animals, but its presence in sensitive organs calls for urgent further investigation.”

The validity of the result is also confirmed by the use of innovative laboratory methods. “The presence of the virus – states Giovanni Di Teodoro, pathologist – was confirmed in the infected tissues through highly specific in situ hybridization techniques, which validated the results obtained through metagenomics. This further reinforces the importance of the discovery and its potential impact.”

At present, it is not possible to state with certainty whether the virus was the direct cause of the respiratory syndrome or whether its presence represents only a co-infection or an incidental finding. However, the possibility that viruses considered specific to arthropods may also infect vertebrates is a topic of growing scientific interest.

The study highlights the strategic importance of genomic surveillance, the integrated use of innovative approaches, and international scientific cooperation to promptly identify emerging or little-known pathogens. An approach that fits fully within the One Health vision of the Istituto Zooprofilattico of Teramo, committed to monitoring the interface between animal, human and environmental health.

“This research – concludes Heidi Auerswald, Virology – paves the way for the development of new projects to understand the biological and pathological impact of Alphamesonivirus-1 in mammals, to decipher the mechanisms that enabled its adaptation, and to assess its zoonotic potential.”