Historically, pine siskins are highly susceptible to Salmonella infections, yet few studies explore their immune response against this pathogen. We looked at pine siskins, lesser goldfinches, American goldfinches, and house finches—following a significant outbreak of avian Salmonella enterica serovar Typhimurium in 2020-21. The research focused on two key hypotheses: that these finch species vary in their innate immune function, measured through bacterial killing assays (BKA), and in their genetic diversity at the Toll-like receptor 4 (TLR4) gene, which plays a crucial role in the immune response against Salmonella. We expected pine siskins to have the weakest immune defense and the lowest genetic diversity at TLR4, given their historical vulnerability to Salmonella. Surprisingly, our results showed significant variation in immune responses, with pine siskins having the highest genetic diversity at TLR4, while house finches, typically more resilient to Salmonella, had the lowest TLR4 variation. Additionally, the three Spinus species (goldfinches and pine siskins) had lower bactericidal ability compared to house finches. These findings provide new insights into the immune dynamics of wild songbirds, particularly why some species are more susceptible to Salmonella infections, and offer valuable data for conservation efforts aimed at protecting vulnerable bird populations from bacterial diseases.

Canine distemper virus (CDV), canine parvovirus (CPV), and canine adenovirus (CAV) pose potential threats to carnivores, including endangered San Joaquin kit foxes (Vulpes macrotis mutica; SJKF). We studied viral exposure in six SJKF populations across urban and exurban areas in California from 2019-2022. Serum from 45 individuals was tested for viral antibody titers, while 395 oculonasal and soft palate swabs were PCR tested for CDV presence that would indicate viral shedding. While no active CDV shedding was detected, antibody titers were detected in nine (20%) SJKF, indicating exposure. Additionally, CDV infection resulted in the death of five SJKF from urban and exurban populations from 2019 - 2023. CPV antibodies were widespread, found in 42 (93.3%) serum samples. CAV antibodies were less common, with only one fox (2.2%) having detectable antibody titers. Although CAV hasn't been diagnosed as a cause of SJKF mortality, it remains concerning due to potential high mortality in young canids. Overall, antibody prevalence for all three viruses was comparable between urban and exurban environments suggesting similar factors influencing viral exposure. These findings emphasize the need for ongoing monitoring of viral threats to SJKF populations, particularly given their endangered status and the potential impact on their conservation.

After rabbit hemorrhagic disease virus 2 (RHDV2) emerged in California in May 2020, an interagency/zoo/academia/non-profit team implemented emergency conservation actions to protect California’s Central Valley endemic, endangered riparian brush rabbit (Sylvilagus bachmani riparius, RBR). Vaccination of ~15% of the estimated RBR population began in September 2020 to minimize disease-caused extinction risk after a single dose vaccine trial on 19 wild RBRs temporarily held in captivity demonstrated safety. All trial RBRs developed antibodies, with titers from 1:10 - 1:160. Seroconversion generally occurred 7-10 days post-vaccine and antibody response was ≥60 days in 12 individuals. A total of 1,217 RBRs have been vaccinated at least once since 2020. Spatially explicit mark-recapture-based density estimates using capture data from Fall 2020-Spring 2022 ranged from 2.66- 62.52 RBRs/hectare. In Spring 2022, RHDV2-caused deaths of three unvaccinated RBRs and one sympatric desert cottontail (S. auduboni) confirmed species susceptibility to RHDV2. No mortalities in vaccinated RBRs were detected. Severe flooding January through June 2023 significantly reduced the RBR population, evidenced by reduced camera-trap detections and ~80% fewer RBR captures post-flood in October-November 2023 as compared to 2020-2022. Vaccination, disease surveillance, and population monitoring are ongoing to protect RBRs and monitor post-flood recovery.

Disease can pose a severe threat to the persistence of threatened and declining wildlife. In recent decades, the pathogenic amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), has contributed to global amphibian declines and extinctions, and innovative mitigation strategies have been required to combat this pathogen. Here, I will discuss efforts to mitigate the impacts of Bd on the federally and state-listed endangered mountain yellow-legged frog, Rana muscosa, in southern California. We have tested both in situ anti-fungal treatments and ex situ immune priming as management strategies for this species. Our approach is ecologically and evolutionarily informed: by using Bd isolated from the release site and treating frogs with site-specific probiotics after clearing their Bd infections, we aim to test whether carefully tailored pre-release treatments can enhance post-release outcomes. Although these Bd mitigation methods are at their infancy, our investigations shed light on Bd dynamics and mitigation strategies in this region and may provide solutions to other threatened amphibian species battling Bd.