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Absence of clinical disease and contact transmission of North American clade 2.3.4.4 H5NX HPAI in experimentally infected pigs.

Absence of clinical disease and contact transmission of North American clade 2.3.4.4 H5NX HPAI in experimentally infected pigs.
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Kaplan BS, Torchetti MK, Lager KM, Webby RJ, Vincent AL,


Kaplan BS, Torchetti MK, Lager KM, Webby RJ, Vincent AL, (click to view)

Kaplan BS, Torchetti MK, Lager KM, Webby RJ, Vincent AL,

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Influenza and other respiratory viruses 2017 07 08() doi 10.1111/irv.12463
Abstract
BACKGROUND
In the fall of 2014, clade 2.3.4.4 highly pathogenic avian influenza (HPAI) subtype H5N8 was introduced into North America by migrating waterfowl from Asia where, through reassortment, novel HPAI H5N2 and H5N1 viruses emerged.

OBJECTIVES
Assess the susceptibility of pigs to North American HPAI clade 2.3.4.4 H5N1, H5N2, and H5N8.

METHODS
Pigs and trachea explants were inoculated with a representative panel of clade 2.3.4.4 HPAI viruses from North America. Nasal swabs, BALF, and sera were collected to assess replication and transmission in challenged and direct contact pigs by RRT-PCR, virus isolation, hemagglutination inhibition (HI), and ELISA.

RESULTS
Limited virus replication was restricted to the lower respiratory tract of challenged pigs, though absent in the nasal passages and trachea cultures, as determined by RRT-PCR in all samples. Seroconversion of inoculated pigs was detected by NP ELISA but was not reliably detected by antigen specific HI. Boost with adjuvanted-virus was required for the production of HI antibodies to assess cross-reactivity between wild-type avian strains. All RRT-PCR and serology tests were negative for contact animals indicating a failure of transmission from primary inoculated pigs.

CONCLUSIONS
Clade 2.3.4.4 H5NX strains can replicate in the lower respiratory tract of swine upon high titer inoculation, though appear to be incapable of replication in swine nasal epithelium in vivo or ex vivo in trachea explants in culture. Infected pigs do not produce high levels of HI antibodies following infection. Collectively, our data show clade 2.3.4.4 HPAI H5NX viruses to be poorly adapted for replication and transmission in swine. This article is protected by copyright. All rights reserved.

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