Fig 2. Summary of shedder impacts on contact birds.

(A) Impact of shedder vaccination status on contacts at 13 and 20 shedder DPI. Contacts positive for virus in qPCR from samples taken at 14 DPC were classified as infected. ‘Diseased’ individuals showed visible symptoms (peripheral nerve enlargement and/or tumours) at necropsy, 8 weeks post-contact, or upon death. ‘Dead’ contacts were those that died or were humanely euthanized before the end of the 8-week experimental period, were infected, and were positive for disease symptoms at necropsy. HVT = vaccinated shedders; PBS = sham-vaccinated shedders. (B) Nonmetric multidimensional scaling plot, for diseased contacts only, of relationships between contact bird disease severity variables and contact bird sex, shedder vaccination status, and shedder FVL. Points are individual contact birds. Grey arrow distance along each axis represents its nonparametric Kendall’s tau correlation with that axis. Opposite-pointing arrows indicate negative associations. Contacts of vaccinated shedders and males therefore had fewer tumours and less extreme nerve enlargement. Points are clustered from bottom-left to top-right into increasing numbers of tissues with tumours, concordant with changing point size; clustering in other directions indicates qualitatively different combinations of tissues with tumours. Variables differ qualitatively (binary, continuous, or ordinal) and so correlation coefficients and hence arrow lengths may not be directly comparable. Shedder DPI effects not shown (see Results text and S1 Table). Underlying data are in Edinburgh DataShare repository (https://doi.org/10.7488/ds/2725). BNE, brachial nerve enlargement; DPC, days post-contact; DPI, days post-infection; FVL, feather viral load; HVT, herpesvirus of turkeys; MD, Marek disease; NMS1, nonmetric multidimensional scaling axis 1; qPCR, quantitative polymerase chain reaction; SNE, sciatic nerve enlargement; VNE, vagus nerve enlargement.