Influenza A Virus (H3N8) in Dogs with Respiratory Disease, Florida

Abstract

Genetic and antigenic characterization established the uniqueness of this virus circulating in dogs.

Diagnostic Application of H3N8-Specific Equine Influenza Real-Time Reverse Transcription Polymerase Chain Reaction Assays for the Detection of Canine Influenza Virus in Clinical Specimens

“…Phylogenetic analysis of 4 Greyhound isolates and 2 pet dog isolates revealed that these viruses were closely related to EIV strains recovered from horses since 2000, belonging to the Florida sublineage of the American lineage of H3N8 EIV. 2,11 The isolation of 4 closely related H3N8 EIV subtype strains from dogs that died in different locations over a 2-year period, together with serologic evidence of widespread infection among Greyhounds in different states, strongly confirmed sustained circulation of CIV involving dog-to-dog transmission of the virus. 2,11,18 Most outbreaks of CI occur in rescued, kenneled, or boarded dogs.…”

“…2,11 The isolation of 4 closely related H3N8 EIV subtype strains from dogs that died in different locations over a 2-year period, together with serologic evidence of widespread infection among Greyhounds in different states, strongly confirmed sustained circulation of CIV involving dog-to-dog transmission of the virus. 2,11,18 Most outbreaks of CI occur in rescued, kenneled, or boarded dogs. 4 Clinical signs of the disease include low-grade fever, lethargy, anorexia, nasal discharge, and prolonged cough.…”

“…4 Clinical signs of the disease include low-grade fever, lethargy, anorexia, nasal discharge, and prolonged cough. 4,11 These signs can mimic those caused by other canine respiratory pathogens. Accordingly, it is especially important to be able to distinguish CIV from other agents capable of causing canine respiratory disease.…”

“…2,4 Sequence analysis of Canine influenza virus (CIV) from the original outbreak (A/canine/FL/43/04) revealed that 8 gene segments of this virus shared $96% nucleotide sequence homology with that of the H3N8 EIV subtype, suggesting that CIV resulted from direct interspecies transmission of EIV to dogs without genetic reassortment. 2,11 The sequence changes in the hemagglutinin gene (H3 HA) are indicative of adaptive evolution of the virus in its new host. Phylogenetic analysis of 4 Greyhound isolates and 2 pet dog isolates revealed that these viruses were closely related to EIV strains recovered from horses since 2000, belonging to the Florida sublineage of the American lineage of H3N8 EIV.…”

“…4,15 Presence of CIV nucleic acid in clinical specimens has been confirmed by traditional reverse transcription polymerase chain reaction (RT-PCR) and real-time RT-PCR assays targeting the matrix (M) gene of Avian influenza virus or by an real-time RT-PCR assay specific for the H3 HA or the M gene of CIV. 4,11,15 Recently, 3 real-time RT-PCR assays targeting the nucleoprotein (NP), M, and H3 HA genes of H3N8 subtype of EIV (EIV NP, EIV M, and EIV HA3 assays, respectively; Table 1) were developed and evaluated. 9 The EIV NP, EIV M, and EIV HA3 primers and probe sets were 100% identical to the published NP, M, and H3 HA sequences of CIV, respectively.…”