Volume 14, Number 8—August 2008
Dispatch
Pathogenicity of Highly Pathogenic Avian Influenza Virus (H5N1) in Adult Mute Swans
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.
