Dynamics of virus shedding and antibody responses in influenza A virus-infected feral swine

Abstract

Given their free-ranging habits, feral swine could serve as reservoirs or spatially dynamic 'mixing vessels' for influenza A virus (IAV). To better understand virus shedding patterns and antibody response dynamics in the context of IAV surveillance amongst feral swine, we used IAV of feral swine origin to perform infection experiments. The virus was highly infectious and transmissible in feral swine, and virus shedding patterns and antibody response dynamics were similar to those in domestic swine. In the virus-inoculated and sentinel groups, virus shedding lasted #6 and #9 days, respectively. Antibody titres in inoculated swine peaked at 1 : 840 on day 11 post-inoculation (p.i.), remained there until 21 days p.i. and dropped to ,1 : 220 at 42 days p.i. Genomic sequencing identified changes in wildtype (WT) viruses and isolates from sentinel swine, most notably an amino acid divergence in nucleoprotein position 473. Using data from cell culture as a benchmark, sensitivity and specificity of a matrix gene-based quantitative reverse transcription-PCR method using nasal swab samples for detection of IAV in feral swine were 78.9 and 78.1 %, respectively. Using data from haemagglutination inhibition assays as a benchmark, sensitivity and specificity of an ELISA for detection of IAV-specific antibody were 95.4 and 95.0 %, respectively. Serological surveillance from 2009 to 2014 showed that ,7.58 % of feral swine in the USA were positive for IAV. Our findings confirm the susceptibility of IAV infection and the high transmission ability of IAV amongst feral swine, and also suggest the need for continued surveillance of IAVs in feral swine populations.

Tissue tropisms of avian influenza A viruses affect their spillovers from wild birds to pigs

“…Animals were transported to the National Wildlife Research Center, Mississippi Field Station, in Mississippi State, MS, USA, where they were quarantined for 1 week. Before the animals were included in the experiments, we confirmed that these feral swine had not been exposed to brucellosis, pseudorabies and IAV using ELISA ((IDEXX, Westbrook, ME) as previously described [54] and that all HI assay results were negative for three testing H4N6 IAVs (MO/15, OS2244, and OS5426), and three endemic human IAVs [i.e., A/California/04/2009(H1N1), A/Switzerland/9715293/2013(H3N2), and A/Hong Kong/4801/2014(H3N2)]. The swine were then housed and fed according to standard protocol, as described elsewhere [54].…”

“…For animal experiments, a total of 26 feral swine (body weight 16–22 kg) were trapped in a rural area of Starkville, MS, USA, by using corral traps similar to those previously described [54]. Animals were transported to the National Wildlife Research Center, Mississippi Field Station, in Mississippi State, MS, USA, where they were quarantined for 1 week.…”

Pathogenesis of Influenza D Virus in Cattle

“…It is also possible that the virus gained host adaptations upon transmission that could have facilitated more efficient replication. Phenotypic changes in influenza viruses due to adaptation to the host have been shown in IAV studies in feral swine, domestic swine, and mice and have also been demonstrated for IDV in the guinea pig transmission model (11)(12)(13)(14). Future studies will characterize the pathogenesis in the contact calves and potentially identify mutations in the isolates recovered from the contact calves.…”

Detection of Antigenic Variants of Subtype H3 Swine Influenza A Viruses from Clinical Samples

“…Swine 1 to 8 were inoculated nasally with virus; swine 9 to 12 were sentinel swine housed in the same room. Among a total of 120 samples collected from these 12 swine, 42 samples with detectable TCID 50 were used in this study (see Table S1 in the supplemental material) (29).…”

“…A total of 120 nasal wash and nasal swab samples were collected for 10 consecutive days postinfection (dpi) from 8 feral swine infected with A/swine/Texas/A01104013/2012 (H3N2) and 4 sentinel feral swine. The details for experimental designs and sample collections were available from a prior publication (29). Among these samples, 42 were tested with a detectable TCID 50 , and these samples were used in this study to test the sensitivity and specificity of the proposed polyPLA method.…”