Abstract
Influenza D virus (IDV) has been increasingly reported all over the world. Cattle are considered the major viral reservoir. Based on the hemagglutinin-esterase (HEF) gene, three main genetic and antigenic clusters have been identified: D/OK distributed worldwide, D/660 detected only in the USA and D/Japan in Japan. Up to 2017, all the Italian IDV isolates belonged to the D/OK genetic cluster. From January 2018 to May 2019, we performed virological surveillance for IDV from respiratory outbreaks in 725 bovine farms in Northern Italy by RT-PCR. Seventy-four farms were positive for IDV. A full or partial genome sequence was obtained from 29 samples. Unexpectedly, a phylogenetic analysis of the HEF gene showed the presence of 12 strains belonging to the D/660 cluster, previously unreported in Europe. The earliest D/660 strain was collected in March 2018 from cattle imported from France. Moreover, we detected one viral strain with a reassortant genetic pattern (PB2, PB1, P42, HEF and NP segments in the D/660 cluster, whilst P3 and NS segments in the D/OK cluster). These results confirm the circulation of IDV in the Italian cattle population and highlight the need to monitor the development of the spreading of this influenza virus in order to get more information about the epidemiology and the ecology of IDV viruses.
Highlights
The circulation of influenza D virus (IDV) has been detected in a wide range of animal species and has been increasingly reported all over the world since its discovery in 2011 [1,2]
Ninety-two nasal swabs and seven lung tissues from 74 farms were positive for Influenza D virus (IDV), of which
The full genome sequencing was performed on positive samples and partial or full-length sequences were obtained from 29 samples by Next generation sequencing (NGS) (18 from isolated viruses and 11 from clinical samples) (Table 1)
Summary
The circulation of influenza D virus (IDV) has been detected in a wide range of animal species and has been increasingly reported all over the world since its discovery in 2011 [1,2]. Cattle are considered the major viral reservoir. Bovine respiratory disease (BRD) is a major health problem of respiratory system occurring worldwide in both dairy and feedlot cattle. Viral agents may produce a clinical syndrome consistent with BRD and their involvement is generally considered as antecedent to, or concurrent with, bacterial infection. Cattle are considered the major IDV reservoir but understanding the possible role of IDV in bovine respiratory disease (BRD) is one of the main focuses of research studies concerning this virus [4,5]. IDV is an Viruses 2019, 11, 1110; doi:10.3390/v11121110 www.mdpi.com/journal/viruses
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