Detection and characterization of an H4N6 avian-lineage influenza A virus in pigs in the Midwestern United States

摘要

Abstract H4Nx viruses were reported in swine in Canada and China, but had not been recognized in swine in the USA. In late 2015, an avian-origin H4N6 influenza A virus was isolated from pigs in the United States during a routine diagnostic investigation of clinical respiratory disease in the herd. Serological analysis from additional pigs at the farm and other pigs within the swine production system indicated that the virus did not efficiently transmit from pig-to-pig and the mode of transmission to swine could not be determined. The isolate was characterized at the molecular level and the pathogenesis and transmission was experimentally evaluated in pigs. Although the virus replicated in the lungs of pigs and caused mild pulmonary lesions, there was no evidence of replication in the upper respiratory tract or transmission to indirect contacts, supporting the findings on the farm. Highlights ? An avian H4N6 influenza A virus was detected and isolated from a pig in Midwestern United States. ? Analysis of clinical samples suggests the H4N6 virus was not widespread in swine. ? The H4N6 replicated efficiently in the lungs of challenged pigs and caused lesions. ? Virus was not detected in the upper respiratory tract of challenged pigs. ? There was no evidence of transmission in contact pigs exposed to challenged pigs.