Four to five week old female BALB/c mice (n=6) were immunized i.n. with active rCPAF, inactive rCPAF, rGST, or PBS (mock) plus IL-12 on day 0, and booster immunizations were given on days 14 and 28. One month after the final immunization, mice were challenged with 5×104 IFU of C. muridarum and pathology was observed on day 80 post challenge. (A) Macroscopic oviduct dilatation. At 80 days post-challenge, animals were euthanized and genital tracts were collected and photographed. The cross sectional diameter for dilated oviducts was measured and the highest one was reported, with mean ± SE per group of mice. Significant reduction in oviduct dilatation with active and inactive rCPAF vaccination compared to PBS or GST (P < 0.05, Student t- test). (B) Microscopic dilatation. Genital tracts were collected, embedded in paraffin blocks, and sectioned (5μm thickness). These sections were stained with haematoxylin and eosin and the extent of dilatation reported as largest oviduct diameter/wall thickness ratio with mean ± SE. Significant difference between mock-vaccinated versus active rCPAF (♠) or inactive rCPAF (♣) vaccinated animals (P ≤ 0.05, Student t test). Results are representative of two individual experiments.