Characteristics of Diagnostic Tests Used in the 2002 Low-Pathogenicity Avian Influenza H7N2 Outbreak in Virginia

Abstract

An outbreak of low-pathogenicity avian influenza (LPAI) H7N2 occurred in 2002 in the Shenandoah Valley, a high-density poultry production region in Virginia. Infected flocks were identified through a combination of observation of clinical signs and laboratory diagnostic tests designed to detect avian influenza (AI) antibodies, virus, or H7-specific RNA. In this report, fitness for purpose of 3 virus/RNA detection assays used during the outbreak was examined: 1) antigen capture enzyme immunoassay (AC-EIA), 2) real-time reverse transcription polymerase chain reaction (RRT-PCR), and 3) virus isolation (VI). Results from testing 762 turkey and 2,216 chicken tracheal swab pooled specimens were analyzed to determine diagnostic sensitivities and specificities of these tests under field conditions using Bayesian techniques for validation of diagnostic tests in the absence of a "gold standard." Diagnostic sensitivities (with 95% probability intervals) in turkeys of AC-EIA and RRT-PCR, in reference to VI, were 65.9 (50.6; 81.3)% and 85.1 (71.9; 95.7)% and of VI 92.9 (78.0; 98.8)% in reference to AC-EIA or 88.7 (76.0; 97.2)% in reference to RRT-PCR; in chickens, diagnostic sensitivities were 75.1 (45.6; 94.2)%, 86.3 (65.9; 97.1)%, and 86.2 (65.8; 97.1)% or 86.3 (66.4; 97.2)%, respectively. Specificities were 99.1 (97.9; 99.8)%, 98.9 (98.0; 99.5)%, and 98.6 (97.4; 99.4)% or 98.8 (97.8; 99.5)% in turkeys and between 99.25% and 99.27% with probability intervals of approximately +/-0.4% for all tests in chickens. Simultaneous use of AC-EIA and RRT-PCR contributed significantly to the rapid control of the outbreak, but the AI RRT-PCR assay with >85% sensitivity and approximately 99% specificity, combined with relatively low cost and fast turnaround, could be used as the sole diagnostic test in outbreaks of LPAI.

Detection of H5N1 High-Pathogenicity Avian Influenza Virus in Meat and Tracheal Samples from Experimentally Infected Chickens

“…There were some discrepancies in test results between the RRT-PCR and the antigen-capture test for tracheal swabs collected between 6 and 18 hr PI, with the antigen-capture tests identifying few positive samples, which is not unexpected because the available antigen-capture tests are less sensitive than RRT-PCR or VI (8,11). For preclinical infected birds, the RRT-PCR test is needed for its greater sensitivity, but for birds that are sick or dead from HPAI virus, either RRT-PCR or antigen-capture tests on tracheal samples provide comparable results.…”

Comparison of Pooling 11 or 5 Oropharyngeal Swabbings for Detecting Avian Influenza Virus by Real-Time Reverse Transcription–PCR in Broiler Chickens

“…At 2 wk of age, broilers in the AIVinfected treatment group were inoculated with 10 5 50% embryo infectious dose per bird with the H7N2 low pathogenicity (LP) AIV strain, chicken/Maryland/Minh Ma/04, via the intranasal route. On days 2, 3,4,5,7,9,11, and 14 postinoculation (PI), O/P swabbings were collected from individual AIV-infected and uninfected control broilers. A goal of the research was to simulate situations of low viral loads in the pools, thus making detection more difficult.…”

“…E-mail: bladman@udel.edu AVIAN DISEASES 56:227-229, 2012 capture immunoassay (ACIA). While both ACIA and RRT-PCR testing are used to carry out active (preslaughter) surveillance programs, RRT-PCR is considered to be essential because it is more sensitive than ACIA for detecting avian influenza virus (AIV) infection (3,4,5). The cost of RRT-PCR, which is approximately 2 to 3-fold greater than ACIA, has had the effect of limiting the number of RRT-PCR tests performed in surveillance programs.…”

“…Pollos de engorde de dos semanas de edad, fueron inoculados por vía intranasal con una cepa del virus de la influenza aviar de baja patogenicidad Pollo/Maryland/ Minh Ma/04 H7N2, o se mantuvieron como controles no inoculados. En los días 2, 3,4,5,7,9,11, y 14 después de la inoculación, se recolectaron hisopos orofaríngeos de las aves infectadas individualmente y se combinaron con cuatro o 10 hisopos de pollos de engorda no infectados para producir 10 replicas de 5 y 11 hisopos, respectivamente. El virus de la influenza aviar fue detectado con facilidad (en un 80% a un 100%) mediante RRT-PCR en las muestra agrupadas con cinco y once hisopos desde los dos a los cinco días después de la inoculación.…”

Do crocodilians get the flu? Looking for influenza A in captive crocodilians

“…In no case did a cloacal swab (in RNAlater s solution or PBS) yield a positive result by RT-PCR, even in the same individuals where the blood or serum sample was positive. RT-PCR is known to be among the most sensitive tests available when performed correctly (Spackman et al, 2002;Elvinger et al, 2007). However, PCR is known to be inhibited in a number of sample types, particularly cloacal swabs and in feces.…”