Swine Influenza A virus (swIAV) may transmit through aerosols. The virus has been detected in air samples collected in affected pig farms  and a relationship between airborne swIAV detection and the number of infected pigs was shown . Here, we report swIAV detection in air samples collected in experimental rooms housing specific-pathogen-free (SPF) pigs without or with maternally-derived antibodies (MDA). Thirty-three MDA- piglets were assigned to 3 independent rooms (rooms 1 to 3) and 33 MDA+ piglets to 3 others (rooms 4 to 6) . In each room there were 2 seeder pigs (intra-tracheally inoculated with A/Sw/France/Cotes d’Armor/0388/09 (H1N1) (106 EID50 in 5 mL) and 4 pen-mates in direct-contact, as well as 5 indirect-contact pigs in a neighboring pen, 30 cm apart. (Figure 1).
Figure 1. An experimental room was composed of two pens. The air sampler collector was placed in-between. The inoculated pigs are colored in red.
The swIAV genome was detected in aerosols from all rooms, from DPI 2 or DPI 4, until the end of the experiment (Figure 2). In each room the viral genome load peaked at DPI 9.
Figure 2. SwIAV genome load in air samples deduced from RT-PCR analyses (45-Ct value)
All indirect-contact (IC) pigs were shown to have been infected. They shed the virus from DPI 4 or DPI 6 depending on their serological status, and until DPI 14 for the last one (Table 1).
Table 1. SwIAV genome detection in nasal secretions of IC pigs. The room was considered positive (in red) when at least 1 out the 5 IC pigs was found RT-PCR positive.
Thus, the swIAV genome was detected in the air 2 days before the first IC piglet shed the virus and still up to 15 days after the last one did (room 2).
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