title: Pathogenesis of highly pathogenic avian influenza A virus (H7N1) infection in chickens inoculated with three different doses.
abstract: To study the pathogenesis of a H7N1 highly pathogenic avian influenza virus strain, specific pathogen free chickens were inoculated with decreasing concentrations of virus: 10(5.5) median embryo lethal dose (ELD(50)) (G1), 10(3.5) ELD(50) (G2) and 10(1.5) ELD(50) (G3). Disease progression was monitored over a period of 16 days and sequential necropsies and tissue samples were collected for histological and immunohistochemical examination. Viral RNA loads were also quantified in different tissues, blood, oropharyngeal swabs, and cloacal swabs using quantitative real-time reverse transcriptase-polymerase chain reaction (RT-qPCR). Clinical signs of depression, apathy, listlessness, huddling and ruffled feathers were recorded in G1 and a few G2 birds, whilst neurological signs were only observed in chickens inoculated with the highest dose. Gross lesions of haemorrhages were observed in the unfeathered skin of the comb and legs, and skeletal muscle, lung, pancreas and kidneys of birds inoculated with 10(5.5) ELD(50) and 10(3.5) ELD(50) doses. Microscopic lesions and viral antigen were demonstrated in cells of the nasal cavity, lung, heart, skeletal muscle, brain, spinal cord, gastrointestinal tract, pancreas, liver, bone marrow, thymus, bursa of Fabricius, spleen, kidney, adrenal gland and skin. Viral RNA was detected by RT-qPCR in kidney, lung, intestine, and brain samples of G1 and G2 birds. However, in birds infected with the lowest dose, viral RNA was detected only in brain and lung samples in low amounts at 5 and 7 days post infection. Interestingly, viral shedding was observed in oropharyngeal and cloacal swabs with proportionate decrease with the inoculation dose. We conclude that although an adequate infectious dose is critical in reproducing the clinical infection, chickens exposed to lower doses can be infected and shed virus representing a risk for the dissemination of the viral agent.
authors.affiliation: Centre de Recerca en Sanitat Animal (CReSA), UAB-IRTA, Campus de la Universitat Autonoma de Barcelona, Bellaterra, Barcelona, Spain.
authors.forename: Aida J
authors.initials: AJ
authors.lastname: Chaves
authors.forename: Nuria
authors.initials: N
authors.lastname: Busquets
authors.forename: Naiana
authors.initials: N
authors.lastname: Campos
authors.forename: Antonio
authors.initials: A
authors.lastname: Ramis
authors.forename: Roser
authors.initials: R
authors.lastname: Dolz
authors.forename: Raquel
authors.initials: R
authors.lastname: Rivas
authors.forename: Rosa
authors.initials: R
authors.lastname: Valle
authors.forename: F Xavier
authors.initials: FX
authors.lastname: Abad
authors.forename: Ayub
authors.initials: A
authors.lastname: Darji
authors.forename: Natalia
authors.initials: N
authors.lastname: Majo
mesh_terms: D000311:Adrenal Glands / Q000821:virology; D000818:Animals; D000956:Antigens, Viral / Q000032:analysis; D002319:Cardiovascular System / Q000473:pathology / Q000821:virology; D002490:Central Nervous System / Q000473:pathology / Q000821:virology; D002645:Chickens / Q000821:virology*; D004064:Digestive System / Q000473:pathology / Q000821:virology; D057916:Influenza A Virus, H7N1 Subtype / Q000235:genetics / Q000472:pathogenicity*; D005585:Influenza in Birds / Q000401:mortality / Q000473:pathology / Q000821:virology*; D007668:Kidney / Q000821:virology; D008221:Lymphoid Tissue / Q000473:pathology / Q000821:virology; D009698:Nucleoproteins / Q000032:analysis; D012367:RNA, Viral / Q000032:analysis; D012137:Respiratory System / Q000473:pathology / Q000821:virology; D012867:Skin / Q000473:pathology / Q000821:virology; D013047:Specific Pathogen-Free Organisms; D014764:Viral Proteins / Q000032:analysis; D014774:Virulence; D017201:Virus Shedding
chemical_list: D000956:Antigens, Viral; D009698:Nucleoproteins; D012367:RNA, Viral; D014764:Viral Proteins