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Comparative Study
. 2012;7(3):e32107.
doi: 10.1371/journal.pone.0032107. Epub 2012 Mar 9.

Highly (H5N1) and low (H7N2) pathogenic avian influenza virus infection in falcons via nasochoanal route and ingestion of experimentally infected prey

Affiliations
Comparative Study

Highly (H5N1) and low (H7N2) pathogenic avian influenza virus infection in falcons via nasochoanal route and ingestion of experimentally infected prey

Kateri Bertran et al. PLoS One. 2012.

Abstract

An experimental infection with highly pathogenic avian influenza (HPAI) and low pathogenic avian influenza (LPAI) viruses was carried out on falcons in order to examine the effects of these viruses in terms of pathogenesis, viral distribution in tissues and viral shedding. The distribution pattern of influenza virus receptors was also assessed. Captive-reared gyr-saker (Falco rusticolus x Falco cherrug) hybrid falcons were challenged with a HPAI H5N1 virus (A/Great crested grebe/Basque Country/06.03249/2006) or a LPAI H7N2 virus (A/Anas plathyrhynchos/Spain/1877/2009), both via the nasochoanal route and by ingestion of previously infected specific pathogen free chicks. Infected falcons exhibited similar infection dynamics despite the different routes of exposure, demonstrating the effectiveness of in vivo feeding route. H5N1 infected falcons died, or were euthanized, between 5-7 days post-infection (dpi) after showing acute severe neurological signs. Presence of viral antigen in several tissues was confirmed by immunohistochemistry and real time RT-PCR (RRT-PCR), which were generally associated with significant microscopical lesions, mostly in the brain. Neither clinical signs, nor histopathological findings were observed in any of the H7N2 LPAI infected falcons, although all of them had seroconverted by 11 dpi. Avian receptors were strongly present in the upper respiratory tract of the falcons, in accordance with the consistent oral viral shedding detected by RRT-PCR in both H5N1 HPAI and H7N2 LPAI infected falcons. The present study demonstrates that gyr-saker hybrid falcons are highly susceptible to H5N1 HPAI virus infection, as previously observed, and that they may play a major role in the spreading of both HPAI and LPAI viruses. For the first time in raptors, natural infection by feeding on infected prey was successfully reproduced. The use of avian prey species in falconry husbandry and wildlife rehabilitation facilities could put valuable birds of prey and humans at risk and, therefore, this practice should be closely monitored.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Pancreatic macroscopic lesions from a falcon experimentally infected with highly pathogenic avian influenza virus H5N1.
Multifocal hemorrhagic necrosis in the pancreas of a falcon infected via the nasochoanal route with A/Great crested grebe/Basque Country/06.03249/2006 H5N1 HPAI virus (5 dpi).
Figure 2
Figure 2. Brain tissue from an experimentally H5N1 HPAI virus-inoculated falcon dead at 5 dpi.
A. Focal area of malacia in the cortex (HE stain). B. Immunohistochemical staining of influenza A virus antigen in brain tissue.
Figure 3
Figure 3. Oral shedding from experimentally infected falcons with avian influenza virus.
Viral RNA shedding detected by RRT-PCR in oropharyngeal swabs of falcons infected via the feeding route or via the nasochoanal route. Ct, cycle of threshold. A. Falcons infected with A/Anas plathyrhynchos/Spain/1877/2009 (H7N2) LPAI virus and euthanized at 11 dpi. B. Falcons infected with A/Great crested grebe/Basque Country/06.03249/2006 (H5N1) HPAI virus.
Figure 4
Figure 4. Distribution of α-2,3 and α-2,6 receptors in the respiratory tract of falcons demonstrated by means of MAAII and SNA lectin histochemistry.
A. Nasal turbinates stained by MAAII lectin. B. Trachea stained by MAAII lectin. C. Lung stained by MAAII lectin. D. Nasal turbinates stained by SNA lectin. E. Trachea stained by SNA lectin. F. Lung stained by SNA lectin.
Figure 5
Figure 5. Distribution of α-2,3 and α-2,6 receptors in the digestive tract of falcons demonstrated by means of MAAII and SNA lectin histochemistry.
A. Proventriculus stained by MAAII lectin. B. Duodenum stained by MAAII lectin. C. Rectum stained by MAAII lectin. D. Proventriculus stained by SNA lectin. E. Duodenum stained by SNA lectin. F. Rectum stained by SNA lectin.

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