Exploration Of Canine Influenza Virus Infection In Horses

With rapid development of horse industry in China,especially in racing and equestrian games,frequent transportation of horses hugely accelerated,which increased the potential of disease spreading.It became a great challenge for horse diseases prevention and control in China.Equine Influenza is one of the mandatory diseases that is required to be inspected for the horses pre and post transportation.Recently,cross-species transmission of type A influenza virus caused widespread concern of the public health worldwide.In 2003,H3N8subtype of equine influenza virus?EIV?caused epidemic canine influenza.For last 10 years,an avian original H3N2 subtype of canine influenza virus?CIV?continuously induced canine influenza worldwide,CIV infected cats and guinea pigs.it is unknow whether CIV infect horse.Since CIV was first isolated in Guangdong province which had the third largest population of dogs and 10th largest number of equestrian clubs in China,there were highly possible of transmission of the influenza virus among dogs,horses,and chickens.Therefore,a pilot investigation of seral-prevalence of CIV-antibodies and an evaluation of CIV in infection of equine cells was carried out to explore the possibility of CIV infection in equine.In this study,serological investigation of CIV antibodies in horses from Guangdong province was performed by HI and antibody neutralization experiments.Horse exhibited sero-positive to H3N2 subtype CIV,with ratio of 17.5%and the highest titer of 1:640.The sero-prevelence showed geographical,breed and age specificity under statistical analysis.This indicated that horses may be naturally infected with CIV in Guangdong province,which should be highly concerned by researchers of public health.In order to further study the possibility of H3N2 subtype CIV infection in horses,equine cells were infected with the CIV,the CPE were observed,TCID₅₀ were determined,immunofluorescence detection of virus and virus replication titer were tested.Similar as EIV,CIV binded?2,3-SA sialic acid receptors,indicating its potential for infection of horses.The CIV also induced similar CPE as EIV,and 48 h was most obvious.In addition,the CIV can be stained in infected cells after 24 h by Immunofluorescence staining though slightly less than EIV.CIV infected horse-derived cells,the virus titer was highest at 48 h,while EIV was the highest titer at 24 h.This indicates that CIV can infect and replicate within horse-derived cells,which should cause the Equine Influenza prevention and control personnel to pay close attention.In summary,the first comprehensive sero-prevelence survey and analysis of CIV antibodies in horses found that CIV can infect fetal equine cells with slightly lower infection and replication ability than that of EIV and CIV may naturally infected horse in Guangdong province.CIV challenge of horses are demanded for further investigation.This study lays the foundation for the study of inter-species transmission of influenza virus and provides reference for the prevention and control of equine influenza in china.