Experimental infection of peridomestic mammals with emergent H7N9 (A/Anhui/1/2013) influenza A virus: Implications for biosecurity and wet markets

Abstract

During 2013, a novel avian-origin H7N9 influenza A virus (IAV) emerged in China and subsequently caused large economic and public health burdens. We experimentally infected three common peridomestic wild mammals with H7N9 (A/Anhui/1/2013) IAV. Striped skunks exhibited the highest burden of disease followed by raccoons and cottontail rabbits. Striped skunks also produced the highest levels of viral shedding (up to 10(6.4)PFU/mL nasal flush) followed by cottontail rabbits (up to 10(5.8)PFU/mL nasal flush) and raccoons (up to 10(5.2)PFU/mL nasal flush). Thus, various mammalian species, especially those that are peridomestic, could play a role in the epidemiology of emergent H7N9 IAV. Mammals should be accounted for in biosecurity plans associated with H7N9 and their presence in wet markets, dependent on species, could lead to increased transmission among interspecific species aggregations and may also pose an elevated zoonotic disease risk to visitors and workers of such markets.

Keywords: Cottontail rabbit; Experimental infection; H7N9; Influenza A virus; Mammals; Mephitis; Pathology; Procyon; Raccoon; Shedding; Skunk; Sylvilagus.

Fig. 1

Average body temperatures of cottontail rabbits (Sylvilagus sp.), striped skunks (Mephitis mephitis), and raccoons (Procyon lotor) during select days postinfection (DPI) following experimental infection with emergent H7N9 (A/Anhui/1/2013) influenza A virus. Vertical bars represent the maximum and minimum temperatures of individual animals during a given DPI. All cottontail rabbits (n=6) are shown through 7 DPI and the remaining three are shown through subsequent DPI. Skunks (n=3) and raccoons (n=3) sampled through 21 DPI are presented.

Fig. 2

Average striped skunk (Mephitis mephitis) mass sampled during even days (n=3) postinfection (DPI) following experimental infection with emergent H7N9 (A/Anhui/1/2013) influenza A virus. Vertical bars represent the maximum and minimum mass of individual skunks on a given DPI.

Fig. 3

Variable severity of bronchopneumonia as a result of experimental infection with H7N9 in raccoons (A,B,C), skunks (D,E,F) and cottontail rabbits (G,H,I). (A) Severe fibrinous and necrotizing pneumonia with alveolar edema and hemorrhage in a raccoon. (B) Epithelial loss and attenuation in terminal bronchioles and severe alveolar edema and infiltration of leukocytes, mainly neutrophils and monocyte/macrophages in alveolar septae and alveoli in lung of a raccoon. (C) Higher magnification of lung of an infected raccoon showing severe alveolar neutrophilic and monocyte/macrophage infiltration and edema. Scattered type 2 pneumocytes (arrows) are hypertrophic. (D) Focally very severe bronchopneumonia in an infected skunk with marked intraluminal accumulation of cellular debris in bronchioles and severe parenchyma consolidation due to inflammatory cell infiltration and alveolar edema and fibrin deposition. (E) Severe necrotizing bronchopneumonia in a skunk with destruction of bronchiolar epithelium (arrows) and luminal plugs composed of cellular debris. The adjacent alveolar tissue is severely infiltrated with neutrophils and monocytes/macrophages. (F) Complete destruction of a terminal bronchiole and necrosis of associated alveoli in the lung of an infected skunk accompanied by severe inflammatory cell infiltration. (G) Lung lobe from an H7N9-infected cottontail rabbit showing complete absence of lesions. (H) Focally restricted pneumonia with marked type 2 pneumocyte hypertrophy and proliferation in a lung lobe of a virus-challenged cottontail rabbit. The pneumocyte reaction reflects regeneration and recovery from mild pneumonia. (I) Focally restricted pneumonia with marked perivascular lymphocyte cuffing and type 2 pneumocyte proliferation in the lung of a cottontail rabbit. Both features reflect recovery and regeneration of the parenchyma. Scale bars indicate 1500 um (D, G), 200 um (A, B, E, H, and I) and 150 um (C, F).