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1. Detection of Leptospira kirschneri in a short-beaked common dolphin (Delphinus delphis delphis) stranded off the coast of southern California, USA

   https://doi.org/10.1186/s12917-024-04111-x  

   Prager, K C; Danil, Kerri; Wurster, Elyse; Colegrove, Kathleen M; Galloway, Renee; Kettler, Niesa; Mani, Rinosh; McDonough, Ryelan F; Sahl, Jason W; Stone, Nathan E; et al (December 2024, BMC Veterinary Research)

   Abstract BackgroundPathogenicLeptospiraspecies are globally important zoonotic pathogens capable of infecting a wide range of host species. In marine mammals, reports ofLeptospirahave predominantly been in pinnipeds, with isolated reports of infections in cetaceans. Case presentationOn 28 June 2021, a 150.5 cm long female, short-beaked common dolphin (Delphinus delphis delphis) stranded alive on the coast of southern California and subsequently died. Gross necropsy revealed multifocal cortical pallor within the reniculi of the kidney, and lymphoplasmacytic tubulointerstitial nephritis was observed histologically. Immunohistochemistry confirmedLeptospirainfection, and PCR followed bylfb1gene amplicon sequencing suggested that the infecting organism wasL.kirschneri. LeptospiraDNA capture and enrichment allowed for whole-genome sequencing to be conducted. Phylogenetic analyses confirmed the causative agent was a previously undescribed, divergent lineage ofL.kirschneri. ConclusionsWe report the first detection of pathogenicLeptospirain a short-beaked common dolphin, and the first detection in any cetacean in the northeastern Pacific Ocean. Renal lesions were consistent with leptospirosis in other host species, including marine mammals, and were the most significant lesions detected overall, suggesting leptospirosis as the likely cause of death. We identified the cause of the infection asL.kirschneri, a species detected only once before in a marine mammal – a northern elephant seal (Mirounga angustirostris) of the northeastern Pacific. These findings raise questions about the mechanism of transmission, given the obligate marine lifestyle of cetaceans (in contrast to pinnipeds, which spend time on land) and the commonly accepted view thatLeptospiraare quickly killed by salt water. They also raise important questions regarding the source of infection, and whether it arose from transmission among marine mammals or from terrestrial-to-marine spillover. Moving forward, surveillance and sampling must be expanded to better understand the extent to whichLeptospirainfections occur in the marine ecosystem and possible epidemiological linkages between and among marine and terrestrial host species. GeneratingLeptospiragenomes from different host species will yield crucial information about possible transmission links, and our study highlights the power of new techniques such as DNA enrichment to illuminate the complex ecology of this important zoonotic pathogen. 

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2. Inferring time of infection from field data using dynamic models of antibody decay

   https://doi.org/10.1111/2041-210X.14165  

   Borremans, Benny; Mummah, Riley_O; Guglielmino, Angela_H; Galloway, Renee_L; Hens, Niel; Prager, K_C; Lloyd‐Smith, James_O (August 2023, Methods in Ecology and Evolution)

   Abstract Studies of infectious disease ecology would benefit greatly from knowing when individuals were infected, but estimating this time of infection can be challenging, especially in wildlife. Time of infection can be estimated from various types of data, with antibody‐level data being one of the most promising sources of information. The use of antibody levels to back‐calculate infection time requires the development of a host‐pathogen system‐specific model of antibody dynamics, and a leading challenge in such quantitative serology approaches is how to model antibody dynamics in the absence of experimental infection data.We present a way to model antibody dynamics in a Bayesian framework that facilitates the incorporation of all available information about potential infection times and apply the model to estimate infection times of Channel Island foxes infected withLeptospira interrogans.Using simulated data, we show that the approach works well across a broad range of parameter settings and can lead to major improvements in infection time estimates that depend on system characteristics such as antibody decay rate and variation in peak antibody levels after exposure. When applied to field data we saw reductions up to 83% in the window of possible infection times.The method substantially simplifies the challenge of modelling antibody dynamics in the absence of individuals with known infection times, opens up new opportunities in wildlife disease ecology and can even be applied to cross‐sectional data once the model is trained. 

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3. Pathogenic Leptospira are widespread in the urban wildlife of southern California

   https://doi.org/10.1038/s41598-023-40322-2  

   Helman, Sarah K; Tokuyama, Amanda_F N; Mummah, Riley O; Stone, Nathan E; Gamble, Mason W; Snedden, Celine E; Borremans, Benny; Gomez, Ana_C R; Cox, Caitlin; Nussbaum, Julianne; et al (December 2023, Scientific Reports)

   Abstract Leptospirosis, the most widespread zoonotic disease in the world, is broadly understudied in multi-host wildlife systems. Knowledge gaps regardingLeptospiracirculation in wildlife, particularly in densely populated areas, contribute to frequent misdiagnoses in humans and domestic animals. We assessedLeptospiraprevalence levels and risk factors in five target wildlife species across the greater Los Angeles region: striped skunks (Mephitis mephitis), raccoons (Procyon lotor), coyotes (Canis latrans), Virginia opossums (Didelphis virginiana), and fox squirrels (Sciurus niger). We sampled more than 960 individual animals, including over 700 from target species in the greater Los Angeles region, and an additional 266 sampled opportunistically from other California regions and species. In the five target species seroprevalences ranged from 5 to 60%, and infection prevalences ranged from 0.8 to 15.2% in all except fox squirrels (0%).Leptospiraphylogenomics and patterns of serologic reactivity suggest that mainland terrestrial wildlife, particularly mesocarnivores, could be the source of repeated observed introductions ofLeptospirainto local marine and island ecosystems. Overall, we found evidence of widespreadLeptospiraexposure in wildlife across Los Angeles and surrounding regions. This indicates exposure risk for humans and domestic animals and highlights that this pathogen can circulate endemically in many wildlife species even in densely populated urban areas. 

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4. Bartonella infections are prevalent in rodents despite efficient immune responses

   https://doi.org/10.1186/s13071-023-05918-7  

   Rodríguez-Pastor, Ruth; Hasik, Adam_Z; Knossow, Nadav; Bar-Shira, Enav; Shahar, Naama; Gutiérrez, Ricardo; Zaman, Luis; Harrus, Shimon; Lenski, Richard_E; Barrick, Jeffrey_E; et al (September 2023, Parasites & Vectors)

   Abstract BackgroundPathogens face strong selection from host immune responses, yet many host populations support pervasive pathogen populations. We investigated this puzzle in a model system ofBartonellaand rodents from Israel’s northwestern Negev Desert. We chose to study this system because, in this region, 75–100% of rodents are infected withBartonellaat any given time, despite an efficient immunological response. In this region,Bartonellaspecies circulate in three rodent species, and we tested the hypothesis that at least one of these hosts exhibits a waning immune response toBartonella, which allows reinfections. MethodsWe inoculated captive animals of all three rodent species with the sameBartonellastrain, and we quantified the bacterial dynamics andBartonella-specific immunoglobulin G antibody kinetics over a period of 139 days after the primary inoculation, and then for 60 days following reinoculation with the same strain. ResultsContrary to our hypothesis, we found a strong, long-lasting immunoglobulin G antibody response, with protective immunological memory in all three rodent species. That response prevented reinfection upon exposure of the rodents to the sameBartonellastrain. ConclusionsThis study constitutes an initial step toward understanding how the interplay between traits ofBartonellaand their hosts influences the epidemiological dynamics of these pathogens in nature. Graphical Abstract 

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5. Using serosurveys to optimize surveillance for zoonotic pathogens

   https://doi.org/10.1101/2024.02.22.581274  

   Clancey, E; Nuismer, SL; Seifert, SN (March 2024, bioRxiv)

   ABSTRACT Zoonotic pathogens pose a significant risk to human health, with spillover into human populations contributing to chronic disease, sporadic epidemics, and occasional pandemics. Despite the widely recognized burden of zoonotic spillover, our ability to identify which animal populations serve as primary reservoirs for these pathogens remains incomplete. This challenge is compounded when prevalence reaches detectable levels only at specific times of year. In these cases, statistical models designed to predict the timing of peak prevalence could guide field sampling for active infections. Here we develop a general model that leverages routinely collected serosurveillance data to optimize sampling for elusive pathogens. Using simulated data sets we show that our methodology reliably identifies times when pathogen prevalence is expected to peak. We then apply our method to two putativeEbolavirusreservoirs, straw-colored fruit bats (Eidolon helvum) and hammer-headed bats (Hypsignathus monstrosus) to predict when these species should be sampled to maximize the probability of detecting active infections. In addition to guiding future sampling of these species, our method yields predictions for the times of year that are most likely to produce future spillover events. The generality and simplicity of our methodology make it broadly applicable to a wide range of putative reservoir species where seasonal patterns of birth lead to predictable, but potentially short-lived, pulses of pathogen prevalence. AUTHOR SUMMARYMany deadly pathogens, such as Ebola, Lassa, and Nipah viruses, originate in wildlife and jump to human populations. When this occurs, human health is at risk. At the extreme, this can lead to pandemics such as the West African Ebola epidemic and the COVID-19 pandemic. Despite the widely recognized risk wildlife pathogens pose to humans, identifying host species that serve as primary reservoirs for many pathogens remains challenging. Ebola is a notable example of a pathogen with an unconfirmed wildlife reservoir. A key obstacle to confirming reservoir hosts is sampling animals with active infections. Often, disease prevalence fluctuates seasonally in wildlife populations and only reaches detectable levels at certain times of year. In these cases, statistical models designed to predict the timing of peak prevalence could guide efficient field sampling for active infections. Therefore, we have developed a general model that uses serological data to predict times of year when pathogen prevalence is likely to peak. We demonstrate with simulated data that our method produces reliable predictions, and then apply our method to two hypothesized reservoirs for Ebola virus, straw-colored fruit bats and hammer-headed bats. Our method can be broadly applied to a range of potential reservoir species where seasonal patterns of birth can lead to predictable pulses of peak pathogen prevalence. Overall, our method can guide future sampling of reservoir populations and can also be used to make predictions for times of year that future outbreaks in human populations are most likely to occur. 

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