Fig. 1

Experimental design. Scheme of the design of the trial, comprising the creation of the naturally-infected Shedder pigs (Step 1) for use in the main transmission trial (Step 2). Step 1a. direct infection of the Inoculation pigs (day 0; challenge dose was 10⁵ TCID₅₀ in a total volume of 4 mL, and the challenge route was intramuscularly (IM) and intra-nasally (IN) with 2 mL IM and 1 mL for each nostril) and Step 1b. infection of Shedder pigs through natural transmission (day 1 to day 6); and Step 2a. re-assortment of the naturally infected Shedder pigs and placement in rooms with naïve Contact pigs (day 7) and Step 2b. removal of the Shedder pigs (day 14). Jagged circles: directly Inoculation pigs; Smooth circles, naturally infected Shedder pigs; Squares, Contact pigs; closed symbol, R+ genotype; open symbol, R− genotype3; Blue, Shedder infection group 1; Red, Shedder infection group 2. Arrows indicate the direction of the movement of pigs (R+ solid arrows; R− open arrows)