Experimental Infection of European Starlings (Sturnus vulgaris) and House Sparrows (Passer domesticus) with Pandemic 2009 H1N1 and Swine H1N1 and H3N2 Triple Reassortant Influenza Viruses
European Starlings (Sturnus vulgaris) and House Sparrows (Passer domesticus) are common peridomestic passerine birds that are often associated with domestic animal production facilities. This association provides a potential means for pathogen transmission between facilities. We inoculated European Starlings and House Sparrows with three non-avian influenza virus strains: two swine isolates (H1N1 and H3N2) and one human isolate representing the H1N1 pandemic strain that originated from swine. No viral shedding was observed in House Sparrows, and shedding was minimal and transient in two of 12 (17%) European Starlings. One of these two infected Starlings seroconverted 14 days after inoculation. These results suggest that these two passerine species are minimally susceptible to current influenza viruses in domestic pigs and therefore pose a negligible risk for transmission between or within swine production facilities.
- [Show abstract] [Hide abstract] ABSTRACT: Influenza A virus (IAV) infections are endemic in pork producing countries around the world. The emergence of the pandemic 2009 human H1N1 influenza A virus (pH1N1) raised questions about the occurrence of this virus in Brazilian swine population. During a 2009-2010 swine influenza virus research project at Embrapa Swine and Poultry (CNPSA), an outbreak of a highly transmissible H1N1 influenza A virus disease was detected in a pig herd in Santa Catarina State, Brazil. The virus caused a mild disease in growing pigs and sows without mortality. Three clinically affected piglets were euthanized. Gross lesions included mild to moderate consolidation of cranioventral areas of the lung. Microscopically, the lesions were characterized by necrotizing obliterative bronchiolitis and bronchointerstitial pneumonia. Immunohistochemistry using a monoclonal antibody against type A influenza virus nucleoprotein revealed positive staining in the nuclei of the bronchiolar epithelial cells. Lung tissue from three piglets and nasal swabs from five sows and four piglets were positive for influenza A by RT-PCR. Influenza virus was isolated from one lung, later confirmed by the hemagglutination test (HA titer 1:128) and RT-PCR. Sequence analyses of Hemmaglutinin (HA) and Matrix (M) genes revealed that the virus was consistent with the pandemic (A/H1N1) 2009 influenza virus strain that circulated in humans. This is the first report of an outbreak of pandemic A/H1N1 influenza virus in pigs in Brazil.
- [Show abstract] [Hide abstract] ABSTRACT: In 1985 a fowl plague-like disease occurred in chickens in Lockwood, Victoria, Australia and caused high mortality. An H7N7 influenza virus was isolated from the chickens (A/Chicken/Victoria/1/85); additionally, an antigenically similar virus was isolated from starlings (A/Starling/Victoria/5156/85) and serological evidence of H7N7 virus infection was found in sparrows. Antigenic analysis with monoclonal antibodies to H7, oligonucleotide mapping of total vRNA, and sequence analysis of the HA genes established that the chicken and starling influenza viruses were closely related and probably came from the same source. There was high nucleotide sequence homology (95.3%) between the HA genes of A/Chick/Vic/85 and a fowl plague-like virus isolated from chickens in Victoria 9 years earlier [A/Fowl/Vic/76 (H7N7)]. The sequence homologies indicated that the A/Chick/Vic/85 and A/Fowl/Vic/76 were derived from a common recent ancestor, while another recent H7N7 virus, Seal/Mass/1/80 originated from a different evolutionary lineage. Experimental infection of chickens and starlings with A/Chick/Vic/1/85 (H7N7) was associated with high mortality (100%), transmission to contact birds of the same species, and virus in all organs. In sparrows one-third of the birds died after infection and virus was isolated from most organs; transmission to contact sparrows did not occur. In contrast, the H7N7 virus replicated in ducks and spread to contact ducks but caused no mortality. These studies establish that the host species plays a role in determining the virulence of avian influenza viruses, and provide the first evidence for transmission of virulent influenza viruses between domestic poultry and passerine birds. They support the hypothesis that potentially virulent H7N7 influenza viruses could be maintained in ducks where they cause no apparent disease and may sometimes spread to other wild birds and domestic poultry.