The Pathogenic Model Establishment Of Equine Influenza Virus In Cats And Immunohistochemistry Pathogen Detection

In recent years,a growing number of pets are improving the quality of our life and promoting social harmony,but the epidemic of influenza in pets not only threatened the health of these dogs and cats, but also had an impact on public health.Since the first outbreak of H3N8 influenza A virus infection in racing dogs in 2004, canine influenza was keeping on circulating in dogs in the United States.Then the case of clinically apparent H3N2 influenza virus infection with kept transmission in canine populations were found in South Korea and Southern China. Furthermore the recent studies reported that cats can be infected with H5N1, H9N2, H7N7, H3N2, H1N1 and other subtypes influenza virus.The cat infected with H5N1 may cause horizontal transmission in the feline populations,it is providing a favorable condition for the replication and spreading of influenza virus.Infection of host cells with the influenza virus is mediated by specific interactions between the viral hemagglutinin(HA) or Neuraminidase(NA) and its cell receptor, oligosaccharides containing sialic acid(SA) residues.Feline respiratory tract epithelial cells include sialic acid α2,3-galactose β-1,3-N-acetyl galactosamine(SA α2,3 gal) receptors.The feline contain two kind of sialic acid receptors may become a mixed host of both influenza virus,avian influenza virus and mammalian influenza virus, and it helpful for the recombination and spreading.The HA gene of canine influenza A(H3N8) virus and equine influenza A(H3N8) virus have some mutations,this found shows that H3N8 equine influenza virus has gradually evolved into a new branch and caused horizontal transmission in the canine populations.Interspecies transmission of equine influenza A(H3N8) virus has resulted in establishment of a canine influenza virus. To determine if something similar could happen with cats,we experimentally infected cats with the equine influenza A(H3N8) virus A/equine/Heilongjiang/SS1/2013(H3N8) and evaluated replication and pathogenicity.The clinical signs and replication were detected.The horizontal transmission was evaluated in feline populations.The domestic cats,9-12 weeks of age was inoculation with virus by intranasal routes.One day after inoculation, 5 cats(contact cohort) were introduced into the same cages.The noninfected cats(control cohort) were housed in a different room. Clinical monitoring began 1 day before virus inoculation and continued daily for the next 14 days. Nasal swab samples were collected daily.We also collected the serum and tissue regularly.The results show that the inoculation group and contact cohort were hyperthermia and showed overt clinical signs included sneezing, coughing, depression, loss of appetite and other symptoms.Influenza virus was detected in inoculation group during postinfection days 2-5 and in contact cohort cats during days 5-7.Virus titers was detected in the inoculated group on days 2-5 and in the contact cohort on days 5-7.Virus shedding is similar in inoculation group at postinfection days 5 and in contact cohort cats at days 7.Experimental cats were euthanized postinfection days 5 and 7,and the tissues was collected.The results reveal that the virus was detected only in the the lungs, trachea and turbinate.The pathological of lungs, trachea and turbinate shows that not only the inoculation group but also contact cohort was lymphocytic infiltration but intensity was less for cats int and contact cohort.The results of immunohistochemical illustrated that influenza virus antigen was detected mainly in the trachea and lungs.Inoculation group and contact cohort show a positive antigen reaction.The experimental results show that,H3N8 equine influenza virus can infect domestic cats by intranasal and cause horizontal transmission.Not only the inoculation group but also contact cohort was detected clinical symptoms,virus shedding and virus replication.In this study, we are initial establishment of an animal models of cat infected with H3N8 equine influenza virus.Our finding of horizontal transmission of EIV among cats is significant.And we build a foundation for the feline influenza virus research.This research not only provide theoretical basis of prevention and virulence of H3N8 equine influenza but also illustrate interspecies transmission of virus.