Anthrax is a disease that affects livestock, wildlife, and humans worldwide; however, its relative impacts on these populations remain underappreciated. Feral swine (Sus scrofa) are relatively resistant to developing anthrax, and past serosurveys have alluded to their utility as sentinels, yet empirical data to support this are lacking. Moreover, whether feral swine may assist in the dissemination of infectious spores is unknown. To address these knowledge gaps, we intranasally inoculated 15 feral swine with varying quantities of Bacillus anthracis Sterne 34F2 spores and measured the seroconversion and bacterial shedding over time. The animals also were inoculated either one or three times. The sera were evaluated by enzyme-linked immunosorbent assay (ELISA) for antibodies against B. anthracis, and nasal swabs were cultured to detect bacterial shedding from the nasal passages. We report that the feral swine developed antibody responses to B. anthracis and that the strength of the response correlated with the inoculum dose and the number of exposure events experienced. Isolation of viable bacteria from the nasal passages of the animals throughout the study period suggests that feral swine may assist in the spread of infectious spores on the landscape and have implications for the identification of environments contaminated with B. anthracis as well as the exposure risk to more susceptible hosts.

The dimorphic, soil-dwelling fungus Coccidioides is the causative agent of coccidioidomycosis and is a reemerging pathogen of human health concern. Despite increasing incidence and isolations of the organism outside of its theoretical environmental range, much of Coccidioides epidemiology, including complete host range, remains unknown. Feral swine (Sus scrofa) are an invasive species distributed throughout the United States that may play a role in fungal ecology due to their behavioral associations with soil. To address this, we evaluated seven feral swine for susceptibility to Coccidioides. After intranasal inoculation with 106.2 arthroconidia of C. posadasii, no pigs displayed signs of clinical disease, nor did any exhibit antibodies by AGID testing. Histopathologic evaluation did not reveal the presence granulomatous lesions, and fungal spherules or endospores were not observed in any of the tissue sections examined, although individuals had significant comorbidities, most notably Metastrongylus nematodes in the lungs. Despite the absence of lesions and organisms histologically, C. posadasii was isolated by culture from the lung and mediastinal lymph node of two pigs, indicating active infection. These results suggest that feral swine are mildly susceptible to acute Coccidioides infection and may aid in fungal dispersal due to the presence of spherules in tissues post-mortem.