Influenza D virus is a member of the Orthomyxoviridae family and represents a distinct subtype of the influenza virus. This viral pathogen primarily affects livestock, particularly cattle, and has been identified globally in various parts of the world. Influenza D virus was first recognized in 2011 from nasal swabs taken from pigs, and subsequently from cattle exhibiting respiratory symptoms. Although the virus has been found to infect other species, including goats, sheep, and even humans, it is primarily associated with respiratory disease in cattle.
In terms of genetic makeup, influenza D virus possesses a single-stranded, negative-sense RNA genome categorized into seven different segments. In terms of morphology, it presents itself as a pleomorphic virus with some spherical particles and others having extended filamentous shapes. The virus is approximately 80-120 nm in size. Similar to other influenza viruses, the influenza D virus contains two major surface glycoproteins, namely hemagglutinin-esterase-fusion (HEF) protein and matrix protein (M). These proteins are crucial for the virus's entry into host cells and for its overall pathogenicity.
In terms of clinical symptoms, influenza D virus infection in cattle can result in a wide range of respiratory manifestations, including nasal discharge, coughing, and fever. In more severe cases, it may progress to pneumonia. Diagnostic tests, such as polymerase chain reaction (PCR) and virus isolation, are utilized to confirm the presence of the virus in suspected cases. While there are currently no specific antiviral treatments available for influenza D virus infection, supportive care measures, including rest, management of secondary bacterial infections, and vaccination against other common respiratory pathogens, are recommended to control and prevent the virus's spread.
