Invasive
feral swine (Sus scrofa) are one of the most important wildlife species for disease surveillance in the United States, serving as a reservoir for various diseases of concern for the health of humans and domestic animals. Brucella suis, the causative agent of swine
brucellosis, is one such pathogen carried and transmitted by
feral swine. Serology assays are the preferred field diagnostic for B. suis
infection, as whole blood can be readily collected and
antibodies are highly stable. However, serological assays frequently have lower sensitivity and specificity, and few studies have validated serological assays for B. suis in
feral swine. We conducted an experimental
infection of Ossabaw Island Hogs (a breed re-domesticated from feral animals) as a disease-free proxy for
feral swine to (1) improve understanding of bacterial dissemination and antibody response following B. suis
infection and (2) evaluate potential changes in the performance of serological diagnostic assays over the course of
infection. Animals were inoculated with B. suis and serially euthanized across a 16-week period, with samples collected at the time of
euthanasia. The 8% card agglutination test performed best, whereas the fluorescence polarization assay demonstrated no capacity to differentiate true positive from true negative animals. From a disease surveillance perspective, using the 8% card agglutination test in parallel with either the buffered acidified plate
antigen test or the Brucella abortus/suis
complement fixation test provided the best performance with the highest probability of a positive assay result. Application of these combinations of diagnostic assays for B. suis surveillance among
feral swine would improve understanding of spillover risks at the national level.