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Volume 14, Number 8—August 2008

Dispatch

Pathogenicity of Highly Pathogenic Avian Influenza Virus (H5N1) in Adult Mute Swans

Donata Kalthoff*, Angele Breithaupt*, Jens P. Teifke*, Anja Globig*, Timm Harder*, Thomas C. Mettenleiter*, and Martin Beer*Comments to Author 
Author affiliations: *Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany;

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Table 1

Distribution of viral genomic load and influenza A antigen in tissues of naive mute swans after challenge infection with highly pathogenic avian influenza virus (H5N1), related to assumed tropism and serologic data*

Test Viral RNA load in tissue, Ct value†
High-dose group
Low-dose group
2 3 4‡ 5 6 8‡ 9‡ 10 11 12§ 13 14
Nasal concha ++ + + ++ + +++ / +++ ++ / (+) /
Trachea / + / (+) (+) (+) / ++ (+) / (+) /
Lung (+) ++ ++ + (+) ++ / +++ (+) / + /
Brain ++ ++ (+) +++ + ++ + ++ ++ / (+) +
Pancreas ++ ++ + ++ (+) +++ / ++ + / ++ /
Adrenal gland ++ +++ (+) ++ (+) +++ (+) +++ (+) / + /
Myocardium / + (+) + / + / ++ (+) / / (+)
Liver + +++ (+) + (+) +++ / +++ (+) / + /
Kidney (+) ++ (+) (+) / ++ (+) ++ (+) / + (+)
Spleen (+) +++ (+) + (+) ++ (+) +++ (+) / (+) /
Bursa fabricii / + + (+) + ++ / ++ + / + (+)
Ovary/testis ++ ++ (+) +++ (+) +++ / +++ / / / /
Proventriculus (+) ++ (+) (+) (+) ++ (+) ++ + / (+) +
Cecal tonsil
(+)
++
(+)
+
(+)

++
/
++
+
(+)
(+)
(+)
Tropism¶
N, EP
N, EP, EN
N
N, EP
N, EP

N, EP, EN
N, EP
N, EP, EN
N, EP
/
N
N
Serologic data
ELISA Pos Neg Pos Pos Neg Neg Pos Neg Pos Pos Pos Pos
SNT 1 ND 1 5.3 ND ND 5.7 ND 5.3 10.3 6.7 8.7
HI 2 ND 2 2 ND ND 7 ND 2 9 8 7
DPI serology
5
0
7
6
0

7
12
7
7
21
10
14
Died or euthanized, DPI 5 5 9 6 6 10 12 10 8 21 10 14

*Viral RNA detected by real-time reverse transcription–PCR (RT-PCR) in swans after challenge infection with highly pathogenic avian influenza virus strain A/Cygnus cygnus/Germany/R65/06 (H5N1). N, neurotropism; EP, epitheliotropism; EN, endotheliotropism; ELISA, Pourquier AI A Blocking ELISA against nucleoprotein; Pos, positive; Neg, negative; SNT, serum neutralization test; [ND100 log2] modified from a previously described procedure (6); ND, not done; HI, hemagglutination-inhibition [log2] using homologous influenza virus (H5N1) as antigen according to standardized methods (7); DPI, days postinoculation.
†Real-time RT-PCR results are presented as cycle of threshold (Ct) values: /, >40; (+), >30–40; +, >25–<30; ++, >20–<25; +++, <20. Boldface indicates marked positive staining by immunohistochemical analysis.
‡Contact animals.
§Animal survived until the end of the study.
¶Tropism as assessed by immunohistochemical analysis.

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