Gross pathological and histopathological changes
Compared with the piglets in the immunized-challenge groups (A1 and A2)
(Fig. 6A b, h and Fig. 6B n, t) and negative control groups (C1 and C2)
(Fig. 6A c, i and Fig. 6B o, u), the piglets in the challenge groups (B1
and B2) showed lesions typical of PRRS, such as consolidation in the
lungs and haemorrhaging in the lymph nodes (Fig. 6A a, g and Fig. 6B m,
s). Histopathology revealed a large amount of inflammatory cell
infiltration, epithelial cell proliferation and significant alveolar
diaphragm widening in the lungs (Fig. 6A d, p) and decreased lymphocyte
and medullary bleeding in the lymph nodes (Fig. 6A j, v) in the
challenge groups (B1 and B2) compared with the negative control groups
(Fig. 6A f, l and Fig. 6B r, x). Notably, there was almost no
pathological damage to the lungs (Fig. 6A e and Fig. 6B q) and only
mildly decreased levels of lymphocytes in the immunized-challenge groups
(A1 and A2) (Fig. 6A k and Fig. 6B w).