Susceptibility of North American ducks and gulls to H5N1 highly pathogenic avian influenza viruses

Abstract

Since 2002, H5N1 highly pathogenic avian influenza (HPA1) viruses have been associated with deaths in numerous wild avian species throughout Eurasia. We assessed the clinical response and extent and duration of viral shedding in 5 species of North American ducks and laughing gulls (Larus atricilla) after intranasal challenge with 2 Asian H5N1 HPAI viruses. Birds were challenged at approximately equal to 10 to 16 weeks of age, consistent with temporal peaks in virus prevalence and fall migration. All species were infected, but only wood ducks (Aix sponsa) and laughing gulls exhibited illness or died. Viral titers were higher in oropharyngeal swabs than in cloacal swabs. Duration of viral shedding (1-10 days) increased with severity of clinical disease. Both the hemagglutination-inhibition (HI) and agar gel precipitin (AGP) tests were able to detect postinoculation antibodies in surviving wood ducks and laughing gulls; the HI test was more sensitive than the AGP in the remaining 4 species.

Figure 1

A female wood duck with severe neurologic clinical signs of disease after intranasal inoculation with an Asian strain of highly pathogenic avian influenza H5N1 virus.

Figure 2

Photomicrographs of visceral organs from a wood duck that died after intranasal inoculation with a highly pathogenic avian influenza H5N1 virus. A) Brain with severe, multifocal to coalescing neuronal necrosis. Note the numerous necrotic neurons (arrowheads). Hematoxylin and eosin (HE) stain; bar =100 μm. B) Brain. Note the viral antigen (red) detected in the nucleus of several neurons. The unaffected brain tissue is blue. Immunohistochemical stain with hematoxylin counterstain; bar = 200 μm. C) Adrenal gland with necrotizing adrenalitis. Note the multiple foci of necrosis (n) surrounded by normal adrenal parenchyma (a). HE stain; bar = 200 μm. D) Pancreas with necrotizing pancreatitis. Note the 2 well-demarcated areas of necrosis (n) within the normal pancreatic tissue (p).