title: Comparison of three rapid detection systems for type A influenza virus on tracheal swabs of experimentally and naturally infected birds.
abstract: The present paper reports of the comparison between three rapid virus detection systems and virus isolation (VI) from pooled tracheal swabs collected from naturally and experimentally infected birds with a low pathogenicity avian influenza virus of the H7N3 subtype. The relative sensitivity, specificity and agreement (K value) were calculated for a commercial antigen capture enzyme immunoassay (AC-EIA) and for two nucleic acid detection tests, a one-step reverse transcriptase-polymerase chain reaction (RT-PCR) and a real-time RT-PCR (RRT-PCR), both targeting the M gene. The results indicate that in experimentally infected turkeys VI was positive from the pooled tracheal swabs collected from day 3 to day 10. One-step RT-PCR was able to detect influenza RNA from samples collected from day 3 to day 12, while RRT-PCR amplified influenza RNA in swabs collected from day 3 to day 15. The AC-EIA test yielded positive results between day 5 and day 10 post-infection. On field samples, the K value between the AC-EIA and VI tests was 0.82. Compared with VI, the relative sensitivity of this test was 88.9% (CI95 = 85.2-92.6) and the relative specificity was 95.7% (CI95 = 93.7-97.7). The K value between the RT-PCR and VI tests was 0.88. Compared with virus isolation, the relative sensitivity of the one-step RT-PCR was 95.6% (CI95 = 93.1-98.0) and the relative specificity was 96.3% (CI95 = 94.4-98.1). The K value between the RRT-PCR and VI tests was 0.92. Compared with virus isolation, the relative sensitivity and specificity of RRT-PCR was 93.3% (CI95 = 90.4-96.3) and 98.4% (CI95 = 97.2-99.6), respectively. Generally speaking, comparison between virus isolation, the AC-EIA test and the two nucleic acid detection methods indicated excellent agreement. Data obtained from both experimental and field study suggest a higher sensitivity of the PCR-based methods compared with the AC-EIA. The economical and practical implications of using one of the rapid tests as an alternative to VI during an avian influenza epidemic are discussed.
authors.affiliation: OIE and National Reference laboratory for Newcastle Disease and Avian Influenza, Instituto Zooprofilattico delle Venezie, Legnaro (PD), Italy. virologia@izsvenezie.it
authors.forename: G
authors.initials: G
authors.lastname: Cattoli
authors.forename: A
authors.initials: A
authors.lastname: Drago
authors.forename: S
authors.initials: S
authors.lastname: Maniero
authors.forename: A
authors.initials: A
authors.lastname: Toffan
authors.forename: E
authors.initials: E
authors.lastname: Bertoli
authors.forename: S
authors.initials: S
authors.lastname: Fassina
authors.forename: C
authors.initials: C
authors.lastname: Terregino
authors.forename: C
authors.initials: C
authors.lastname: Robbi
authors.forename: G
authors.initials: G
authors.lastname: Vicenzoni
authors.forename: I
authors.initials: I
authors.lastname: Capua
mesh_terms: D000818:Animals; D007124:Immunoenzyme Techniques / Q000379:methods; D009980:Influenza A virus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D005585:Influenza in Birds / Q000175:diagnosis*; D011201:Poultry Diseases / Q000175:diagnosis* / Q000821:virology*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity; D014132:Trachea / Q000821:virology; D014422:Turkeys