title: No evidence of horizontal infection in horses kept in close contact with dogs experimentally infected with canine influenza A virus (H3N8).
abstract: BACKGROUND
  Since equine influenza A virus (H3N8) was transmitted to dogs in the United States in 2004, the causative virus, which is called canine influenza A virus (CIV), has become widespread in dogs. To date, it has remained unclear whether or not CIV-infected dogs could transmit CIV to horses. To address this, we tested whether or not close contact between horses and dogs experimentally infected with CIV would result in its interspecies transmission.
  
  
  METHODS
  Three pairs of animals consisting of a dog inoculated with CIV (10(8.3) egg infectious dose 50/dog) and a healthy horse were kept together in individual stalls for 15 consecutive days. During the study, all the dogs and horses were clinically observed. Virus titres in nasal swab extracts and serological responses were also evaluated. In addition, all the animals were subjected to a gross pathological examination after euthanasia.
  
  
  RESULTS
  All three dogs inoculated with CIV exhibited clinical signs including, pyrexia, cough, nasal discharge, virus shedding and seroconversion. Gross pathology revealed lung consolidations in all the dogs, and Streptococcus equi subsp. zooepidemicus was isolated from the lesions. Meanwhile, none of the paired horses showed any clinical signs, virus shedding or seroconversion. Moreover, gross pathology revealed no lesions in the respiratory tracts including the lungs of the horses.
  
  
  CONCLUSIONS
  These findings may indicate that a single dog infected with CIV is not sufficient to constitute a source of CIV infection in horses.
authors.affiliation: Epizootic Research Center, Equine Research Institute, the Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi, 329-0412, Japan. yamanaka@epizoo.equinst.go.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamanaka
authors.forename: Manabu
authors.initials: M
authors.lastname: Nemoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Bannai
authors.forename: Koji
authors.initials: K
authors.lastname: Tsujimura
authors.forename: Takashi
authors.initials: T
authors.lastname: Kondo
authors.forename: Tomio
authors.initials: T
authors.lastname: Matsumura
authors.forename: Masanori
authors.initials: M
authors.lastname: Muranaka
authors.forename: Takanori
authors.initials: T
authors.lastname: Ueno
authors.forename: Yuta
authors.initials: Y
authors.lastname: Kinoshita
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Niwa
authors.forename: Kazuya I P J
authors.initials: KI
authors.lastname: Hidari
authors.forename: Takashi
authors.initials: T
authors.lastname: Suzuki
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D004283:Dog Diseases / Q000473:pathology / Q000635:transmission* / Q000821:virology; D004285:Dogs; D006385:Hemagglutination Inhibition Tests / Q000662:veterinary; D006734:Horse Diseases / Q000473:pathology / Q000635:transmission* / Q000821:virology; D006736:Horses; D053123:Influenza A Virus, H3N8 Subtype / Q000302:isolation & purification*; D008168:Lung / Q000382:microbiology / Q000473:pathology; D009297:Nasal Mucosa / Q000821:virology; D009976:Orthomyxoviridae Infections / Q000635:transmission / Q000662:veterinary* / Q000821:virology; D013290:Streptococcal Infections / Q000473:pathology; D018502:Streptococcus equi / Q000276:immunology; D017201:Virus Shedding
chemical_list: D000914:Antibodies, Viral