Knowledge, attitudes, and practices (KAP) studies help identify priority groups for control interventions. They include multiple factors, such as threat perception (encompassing perceived susceptibility and severity of a health risk) and sociodemographic data, which have been shown to be associated with individual prevention and control measures for mosquito-borne diseases. However, their application to tick-borne diseases (TBDs) remains largely unstudied in limited-resource settings. Ehrlichia canis, transmitted by Rhipicephalus sanguineus s.l. ticks, is highly prevalent in Iquitos, Peru, a city in the Peruvian Amazon. We analyzed data from a questionnaire completed by 285 dog owners in Iquitos to assess whether the perceived threat from ticks and TBDs is linked to preventive measures for homes and dogs. Secondary aims included examining the associations between TBD awareness and preventive/control measures, as well as identifying sociodemographic factors linked to these measures and threat perception. We used simple and multiple regression models to evaluate the associations of interest. We found that 31.6% of participants (n = 90) were unaware that TBDs could occur in humans. This group tended to be older, with lower education levels and lower income. Only a small portion of the included participants reported using preventive/control measures. After adjusting for sociodemographic factors, TBD awareness was associated with a higher likelihood of home spraying. Furthermore, those who perceived TBDs as moderate diseases were marginally more likely to apply spray acaricide to their dogs, while those who perceived these diseases as severe to very severe were more likely to administer oral acaricides to their dogs. These findings highlight variability in the link between threat perception and preventive measures. Results suggest TBD awareness campaigns may benefit from focusing on older individuals with lower education and income, while educational efforts promoting effective prevention measures like acaricidal pills should target all dog owners. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement his project was supported by the Fogarty International Center of the National Institutes of Health (D43 TW007393 to AGL) entitled Emerge: Emerging Diseases Epidemiology Research Training. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH. This project was also supported by the University of California Davis Continuing Graduate Student Internal Fellowship (awarded to CF). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: IRB of Universidad Peruana Cayetano Heredia gave ethical approval for this work. DIRESA (Direcciones Regionales de Salud) gave ethical approval for this work. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present work are contained in the manuscript and its supplementary files.

Ticks (Ixodida: Ixodidae) encounter ash after wildfires or controlled burns-either directly or via wildlife that bathe in ash. Despite its use to control ectoparasites in traditional ethnoveterinary practices, the effects of plant-derived ash remain unstudied. We evaluated ash from three tree species that grow in California-coast redwood (Sequoia sempervirens (D.Don) Endl.; Cupressaceae), California bay laurel (Umbellularia californica (Hook. & Arn.) Nutt.; Lauraceae), and non-native Tasmanian blue gum eucalyptus (Eucalyptus globulus Labill.; Myrtaceae)-on survival and behavior of four ixodid tick species: Ixodes pacificus Cooley & Kohls (larvae, adult females), Dermacentor occidentalis Marx (larvae, adults), D. similis Lado, Glon & Klompen (adults), and D. albipictus Packard (larvae). Treatments included ash, two commercial acaricidal dusts (diatomaceous earth and kaolin clay), and a negative control. Eucalyptus ash significantly reduced survival in I. pacificus larvae and females and D. occidentalis larvae, with effects comparable to positive controls. Bay ash showed moderate lethality in I. pacificus females and D. occidentalis larvae. Redwood ash had strong effects only on D. albipictus larvae. Dermacentor species showed low overall susceptibility; larvae were more affected than adults, which showed no lethal effects. Our findings suggest that ash type, tick species, and life stage influence outcomes. This is the first laboratory study to show the effects of plant ash on ticks, supporting ash as a potential alternative for tick control and highlighting fire's indirect role in tickborne disease dynamics.

Introduction: Vitamin E and selenium are vital micronutrients that play key roles in metabolic functions and antioxidant defense, directly influencing equid health. There are no published reference intervals for concentrations of these micronutrients in healthy donkeys. Methods: We compared serum vitamin E and whole blood selenium concentrations in wild, recently captured donkeys with concentrations in donkeys who had been managed in captivity for at least half a year at the time the blood was drawn. In addition, we assessed hematology and serum biochemistry parameters of a subset of the donkeys. We also indirectly analyzed the diet of wild donkey herds using next-generation sequencing of fecal samples. Our last goal was to establish reference intervals for vitamin E and selenium concentrations in wild and rescued donkeys. To do so, we conducted a cross-sectional study of 113 donkeys from Saline Valley and Butte Valley in Death Valley National Park (DVNP), and captive donkeys from Davis, CA, and San Angelo, TX. Results: Wild donkeys had significantly higher vitamin E concentrations (p < 0.001, difference = 180 mu g/dL, CI = 132-228 mu g/dL, Tukey multiple comparisons of means test). Captive donkeys, however, had significantly higher selenium concentrations (p < 0.001, difference = 4.97 mu g/dL, 95% CI = 3.51-6.43 mu g/dL, Tukey multiple comparisons of means test), particularly compared to the wild ones from the Butte Valley population. Reference intervals were established for these micronutrients in wild donkeys. The vitamin E reference range for wild female donkeys was 211-754 mu g/dL and for wild male donkeys was 164-780 mu g/dL; the selenium reference range for wild female donkeys was 8-21 mu g/dL and for wild male donkeys was 12-26 mu g/dL. The fecal analysis found a mixed feeding behavior in the wild donkeys, with both grazing and browsing elements, which may explain the relatively high concentrations of these nutrients. Discussion: This study characterizes the dynamics of vitamin E and selenium concentrations in wild donkeys from Death Valley compared to captive populations, establishing species-specific reference intervals to enhance their management.

Obligately intracellular rickettsiae cause a broad spectrum of disease in humans and animals, ranging from mild illness to life-threatening infections. Multiple species co-circulate along the southern United States of America-northern Mexico border, yet their seroprevalence in susceptible hosts remains incompletely understood. Dogs serve as key amplifying hosts for several of these pathogens, including Rickettsia rickettsii and Rickettsia massiliae, and have been shown to be infected by flea-borne Rickettsia typhi and Rickettsia felis. To better characterize exposure and potential co-infection patterns, we conducted a large binational seroepidemiologic study of 779 dogs from urban households and shelter settings across seven subregions along both sides of the border. Using a custom multiplex micro-immunofluorescence assay, we simultaneously screened for antibodies to R. rickettsii, R. massiliae, R. typhi, and R. felis. Overall, 41.2% of dogs were seroreactive to at least one pathogen, with the highest seroprevalence for R. felis (19.3%), followed by R. massiliae (15.7%), R. typhi (14.5%), and R. rickettsii (9.8%). Co-seroreactivity was common, particularly between R. typhi and R. felis, with 34.2% of R. typhi-seroreactive samples also seroreactive to R. felis, and 16.7% exhibiting high titers to both. In contrast, R. rickettsii and R. massiliae showed limited overlap (15.2% co-seroreactive; 6.4% with high titers), suggesting possible cross-protection or competitive exclusion. Spatial analyses revealed distinct geographic patterns: R. massiliae predominated in western Baja California, R. rickettsii was concentrated in Mexicali and the Rio Grande Valley, and R. felis was widely distributed. Seroreactivity patterns were generally consistent across age and sex but varied modestly between shelter and neighborhood dogs, particularly for R. typhi. These findings highlight the complex ecology of rickettsial pathogens in a binational context, underscore the importance of dogs as sentinels for human risk, and provide a foundation for future studies on vector-host-pathogen interactions, cross-protective immunity, and spatial epidemiological risk.

Disease can threaten endangered species by affecting fitness and survival, suppressing population growth and species recovery. Herein, we investigated three gastrointestinal pathogens-Giardia, Cryptosporidium, and Helicobacter-that could negatively affect the endangered Amargosa vole (Microtus californicus scirpensis). We used PCR testing to determine the presence of the target parasites in 76 fecal samples from 71 Amargosa voles collected during summer 2021 in four marshes in Tecopa, California, USA. Overall, 51 (72%) of 71 voles were PCR positive for Giardia microti, 48 (68%) of 71 for Cryptosporidium spp., and 100% for Helicobacter spp. There were no significant associations between G. microti infection and sex, body condition score, or source marsh. Cryptosporidium sp. infection was significantly more prevalent in smaller marshes. More than half of the individuals sampled (39/71, 55%) were PCR positive for both Giardia and Cryptosporidium spp. upon initial sampling. This study provides foundational information regarding environmentally transmitted parasites in populations of Amargosa voles. Further studies are needed to understand and manage the adverse effects of disease and other threats for the survival of the Amargosa vole.

We explored a compartment “susceptible-infected-recovered” model to prioritize and test the effectiveness of dog- and tick-based interventions against Rocky Mountain spotted fever and its tick vector Rhipicephalus sanguineus s.l. In the face of increasingly urban epidemics of RMSF with high case fatality, particularly targeting marginalized communities, wrap-around campaigns (comprising all or some of canine culling, fertility control, and restraint to property; on-dog and environmental acaricide; and education and awareness programs for public health workers and at-risk residents) are unsustainably resource-intensive and may lack efficacy in managing the very hard to control tick. Our model allows us to strategize interventions and develop an optimized campaign against RMSF, using parameters associated with the epidemic in Ensenada, Baja California as an example. Combining usage of acaricides on dogs and the environment optimized success as measured by up to 10 years of no new canine cases, a proxy for human cases, as well as reduced tick burden. Success was greater when the campaign was begun in winter or spring and achieved at least 60 % coverage. This combination was considerably more successful than either dog or environmental acaricide alone, culling of dogs which was only successful with 100 % of dogs removed, and spay/neuter campaigns which did not reduce tick burdens. However, spay/neuter of outside dogs as an adjunct to the acaricide campaign helped stabilize the canine population and encouraged herd immunity. Although parameterized for Ensenada, the model can easily be run for other communities where data on canine tick burden and tick life history traits are available, in order to tailor intervention details such as optimal timing, coverage, and re-application frequency even when public health resources are limited.

RMSF, a tickborne infection caused by Rickettsia rickettsii, produces severe and fatal disease in humans and dogs. Since the beginning of the 21st century, cases have risen dramatically, most notably in Mexico and Brazil, where outbreaks occur in urban centers including cities with populations of > 1,000,000 persons. Reported case fatality rates can exceed 50%. Factors consistent with high case fatality include lack of awareness of disease ecology, limited capacity for diagnosis, and delay in appropriate antimicrobial treatment. The emergence of urban hyperendemic foci has been leveraged by 2 distinct but similar anthropogenic events that create disproportionately high numbers of vertebrate amplifiers of R rickettsii, as well as the tick species that transmit this pathogen in proximity with dense human populations. This often occurs in neighborhoods with a highly marginalized at-risk population that includes persons in poverty and particularly children, and health management systems that are under-resourced. We discuss strategies to reduce host dog populations, particularly in Mexico, and capybaras in Brazil. We review challenges to the control of tick populations in these settings. Robust systems are required to enhance awareness of RMSF among medical practitioners and people at risk of RMSF. Public health campaigns should incorporate innovative behavioral science (eg, diverse learning models, motivational interviews, and gamification) to increase prevention and understanding within communities. While anti-Rickettsia or anti-tick vaccines will be necessary to resolve this One Health crisis, impactful implementation will require data-driven and multiple-target innovations to address challenges with hosts, ticks, medical systems, and public welfare. The companion Currents in One Health by Foley, Backus, and L & oacute;pez-P & eacute;rez, JAVMA, March 2025, addresses helpful information for the practicing veterinarian.

The lone star tick (LST), Amblyomma americanum, is an aggressive human biter and important vector of the causative agents of tick-borne diseases. As geographic ranges of multiple Amblyomma species rapidly expand due to habitat changes and human and other animal movement patterns, there are concerns for establishment of LST in US states with suitable climates, such as California, especially given a dearth in gaps in tick surveillance. Importantly, previous niche modeling confirmed habitat in California along the length of the coast and coast range mountains. We sought data on LSTs and LST risk from 30 different entities including companies that identify and test ticks, natural history and entomology museums and collections, experts, and large databases. These queries and published records yielded records of 76 LSTs from California as well as two Amblyomma cajennense sensu lato, one Amblyomma sabanerae, one Amblyomma maculatum, and five Amblyomma dissimile. Among LSTs, there were 18 adult females, ten males, 13 adults for which sex was not recorded, 22 nymphs, two larvae, and 11 with no stage data. LSTs were recorded only during late spring through late summer, with all three feeding stages superimposed temporally. Active surveillance was conducted at nine sites considered high-risk due to earlier records of LSTs or high probability of establishment on niche modeling, using tick flagging, monitoring ovine and cervid hosts, and circulating a flier; no LSTs were recovered in this activity. We assessed risk for establishment of LSTs in California using invasion theory, prior niche modeling, literature review of ecological constraints on LSTs within their current range, data acquired in retrospective and prospective segments of this study, and expert consultation. Elevated risk is expected particularly along coastal California. Although some of these ticks likely were transported from out of state endemic regions, the findings of 76 LSTs, including all three feeding stages, in multiple counties raises concern that establishment in the future could occur in California.

Background: Surveillance is important in addressing the significant public health concerns posed by tick-borne diseases. However, the southwestern U.S. presents particular challenges due to diverse tick fauna and varied ecologies. Methods: From 2021 to 2022, we conducted a partner-based tick surveillance program in Arizona and California to assess the presence of Rickettsia spp. pathogens and species composition of tick vectors. Results: A total of 913 ticks was collected, comprising in descending abundance Rhipicephalus sanguineus, Dermacentor similis, Ixodes pacificus (I. pacificus), Argas sp., Otobius megnini, and Haemaphysalis leporispalustris. Arizona submitted predominantly brown dog ticks (90.05% of all ticks from Arizona), while California showed greater tick species richness with five species identified. No Rickettsia rickettsii was detected, but a variety of other Rickettsia spp. was found in ticks from both Arizona and California and included Rickettsia rhipicephali (R. rhipicephali), Rickettsia massiliae, and Rickettsia monacensis-like rickettsial agents of I. pacificus, and two rickettsial organisms that were not identified to species: one Rickettsia montanensis or Rickettsia raoultii-like, and the other most similar to Candidatus Rickettsia tarasevichiae (R. tarasevichiae). Conclusion: This research contributes to our understanding of tickborne diseases in the southwestern U.S., and emphasizes the need for targeted surveillance and intervention initiatives in a region with complex relationships among ticks, hosts, and Rickettsia species. In particular, the finding of an apparently novel pairing of an unknown Argas sp. tick and R. tarasevichiae-like organism suggests that argasid species are an important target for future research. In addition, the results-both tick species submitted and resulting Rickettsia spp. identified-highlights the strengths and potential biases associated with a partner-based sampling method for tick surveillance.

Within 1 yr, two cases of iron storage disease (hemochromatosis) were identified in a breeding colony of endangered Amargosa voles (Microtus californicus scirpensis). This study was designed to investigate the extent of excessive hepatic iron accumulation (iron overload with or without tissue damage) in the colony and identify risk factors such as age, sex, parity, lineage, diet, or housing that could influence management decisions for a population meant to propagate a vanishing species. The two affected voles had periportal to panlobular hepatocellular and Kupffer cell Prussian blue-positive pigment accumulation associated with hepatocellular degeneration and necrosis. By mass spectroscopy, hepatic iron content in the two affected voles was 34,000 and 6,100 parts per million (ppm) compared with 6,800 and 400 ppm in two unaffected voles. To determine the prevalence and identify risk factors, a study set of 45 voles from the pathology archives was selected within representative age groups and between sexes. The paraffin-embedded liver from study set voles was stained with Prussian blue for ferric iron. Prussian blue-positive staining was semiquantitatively scored and quantified using automated image analysis of binary pixels per region of interest. Four additional voles with excessive hepatic iron accumulation were identified within the study set. Age, diet, and types of housing were not risk factors, but female sex and lineage were risk factors. All six voles with elevated hepatic iron as measured by digital analysis or mass spectroscopy or both were female. Excluding affected voles, females had a significantly higher hepatic Prussian blue-positive signal than males. No association was identified between hepatic Prussian blue-positive signal and parity. Pedigree analysis revealed that five of six voles with elevated hepatic Prussian blue-positive signal were related to a single male founder (identification 4585). Excessive hepatic iron accumulation in this captive Amargosa vole colony is, thus, associated with female sex and was potentially heritable.

This field study describes the abundance of ticks and the prevalence of tick-borne pathogens in two hiking areas, Stebbins Cold Canyon (SCC) and Skyline Wilderness Park (SKY), in northern California. These areas have experienced extreme weather events, including wildfire, drought, and heavy rainfall, which have changed the environment. Questing ticks were collected over nine months, identified to species, and screened for tick-borne pathogens using qPCR. Four hundred and fifty-nine ticks were collected, including 54 adults from SCC and 405 from SKY, consisting of 279 (68.9%) larvae, 2 (0.5%) nymphs, and 124 (30.6%) adults. At SCC, Ixodes pacificus and Dermacentor occidentalis accounted for 92.6% (50/54) and 7.4% (4/54), respectively. At SKY, I. pacificus (16.8%, 68/405), D. occidentalis (12.3%, 50/405), D. similis (0.7%, 3/405), and D. albipictus (70.4%, 285/405) were collected. Overall, the prevalence of tick-borne pathogens was low in the collected ticks. Borrelia burgdorferi sl (0.8%, 1/121) and Rickettsia rhipicephali (1.7%, 2/121) were found at SKY. Rickettsia tillamookensis was identified at SCC and SKY with a prevalence of 3.7% (2/54) and 1.7% (2/121), respectively. Babesia duncani was identified in 3.7% (2/54) and 1.2% (5/405) of ticks at SCC and SKY, respectively. These findings suggest that multiple tick species can withstand extreme weather events, providing further data regarding the effects of weather extremes and climate change on tick populations and pathogen prevalence. This study is one of the first to report B. duncani in I. pacificus ticks in California, particularly in Solano County.

Ehrlichia canis is a tick-borne bacterium that causes a potentially fatal disease in dogs called Canine Monocytic Ehrlichiosis. In this cross-sectional study, we used a One Health framework to identify statistical associations between E. canis infection in dogs and multiple dog-related, human and environmental factors in Iquitos, Peru. Due to the lack of consensus regarding the positivity threshold for E. canis qPCR assays, we also evaluated if the factors associated with infection remained conserved regardless of the Ct value cut-off used: Ct<35, a conservative but commonly accepted Ct cut-off for bacterial screening, or Ct ≤40, which has been used in several E. canis studies. Under the more conservative scenario, we found that the prevalence of E. canis among dogs was 19.6% (95% CI 15.8-23.9%). Additionally, we showed that risk factor analyses utilizing a qPCR Ct cut-off of 35 or 40 (with conventional PCR confirmation for samples with a Ct>35) yield comparable results in statistical models, although some differences should be considered. Our findings suggest that in Iquitos, Peru, interventions to prevent E. canis infection should prioritize dogs living in houses with corrugated iron walls. Additionally, comprehensive strategies targeting dogs that have recently traveled and incorporating neutering/spaying and widespread acaricide programs may also prove beneficial. We also discuss the challenges encountered during molecular testing for E. canis detection, highlighting the broader difficulties of studying poorly understood intracellular pathogens in Global South countries.

Rocky Mountain spotted fever (RMSF) kills people and dogs in rural communities throughout the Americas and in urban epidemics in Brazil and Mexico. The companion Currents in One Health by Foley et al, AJVR, March 2025, addresses the urban ecology of this devastating disease across the Americas. Cases acquired from Dermacentor spp ticks are sylvatic and sporadic, in contrast with peridomestic cases from Rhipicephalus sanguineus sensu lato, which relies on dogs as hosts. Since the early 2000s, RMSF reemerged in northern Mexico with at least 9,152 human cases and case mortality up to 50%. These cases tend to occur where people are impoverished and have marginal access to medical care. Data on RMSF in dogs are sparse, although dogs are sentinels for human risk. The presence of roaming dogs in neighborhoods is associated with human cases, canine seroprevalence, and tick abundance. Dogs and people share hematological and clinical chemical findings and results of targeted diagnostic tests. Diagnosis requires PCR confirmation or rising convalescent titers, although seropositivity can be a cross-reaction with other rickettsial organisms. Suspect cases should be treated with doxycycline immediately. Coinfection with other R sanguineus-transmitted pathogens is common. Veterinarians in clinical practice can help families manage RMSF risk with client education and provide tick preventive medication, although the considerable cost is a barrier. Veterinarians can also advise how to manage tick infestations in a home, recognizing that eradicating R. sanguineus is very difficult. To reduce roaming and canine population sizes, veterinarians should promote canine spay, neuter, and restraint to the home.

Rickettsiae are a family of ectoparasite-borne bacteria that can produce high morbidity and mortality among humans. There are scarce data on rickettsial ecology in rural areas of the Peruvian Amazon basin, where seroprevalence has not been determined, and the identities of animals acting as reservoirs of these bacteria are not known. We conducted a cross-sectional study in Zungarococha (between 2019 and 2021), a rural community located approximately 20 km away from Iquitos city. Blood samples were collected from humans (175), dogs (123), and cats (12). Blood samples and tissues were collected from black rats (84). Finally, we collected fleas from dogs and cats (222), ticks from dogs (91), and mites from black rats (32). Blood samples from humans, dogs, cats, and black rats were analyzed by indirect immunofluorescence assays (IFA) to detect IgG antibodies against rickettsias. We screened ectoparasites and black rat tissues by real-time-PCR (qPCR). Positive ectoparasites were further assessed by PCR and DNA amplicon sequencing. Non-parametric tests were used to evaluate factors associated with being seropositive among human adults. IgG seroprevalences were 38.3 %, 58.5 %, 16.7 % and 48.1 % among humans, dogs, cats, and rats, respectively. Among humans, only male gender was statistically associated with having IgG antibodies against Rickettsia spp. (p-value=0.049, chi-square test). Different ectoparasites were identified, including Ctenocephalides felis from cats and dogs, Rhipicephalus sanguineus s.l. from dogs, and Laelaps nuttalli from black rats. Rhipicephalus sanguineus s.l. (2/91 ticks) and Ct. felis (53/56 fleas and 55/55 flea pools) were qPCR-positive for Rickettsia spp. Recovered genetic material from 53 Ct. felis was sequenced and all were identified as Rickettsia asembonensis. All tissue samples from black rats were negative by qPCR. Humans, dogs, cats, and black rats are exposed to spotted fever group rickettsiae in rural areas surrounding Iquitos. As reported in urban areas, R. asembonensis is the main Rickettsia species circulating in rural areas surrounding Iquitos and Ct. felis appears to be the main vector.

A Rocky Mountain spotted fever (RMSF) epidemic has spread through the state of Baja California, Mexico over the last decade and a half, beginning in Mexicali, and subsequently to Tijuana and to Ensenada by 2018. In October of 2022, we surveyed dogs and homes in randomly selected Áreas Geoestadisticas Básicas (AGEBs) with and without reported human cases. Brown dog ticks ( Rhipicephalus sanguineus sensu lato) were found on 33.9% of dogs and in the yards of 23.6% of homes. Homes from AGEBs with cases had over a 6-fold increased odds of ticks being present in the yard than AGEBs without reported cases. Both dogs that were permitted to roam and the presence of roaming dogs in the neighborhood were strongly associated with tick infestation of dogs and homes. No ticks or blood samples were polymerase chain reaction-positive for Rickettsia (R.) rickettsii , the causative agent of RMSF, although 54.6% of dogs were seropositive for spotted fever group rickettsiae, and 17.4% were seropositive for typhus group rickettsiae. R. massiliae and R. felis were detected in eight (1.3%) and 29 (4.8%) ticks, respectively; and R. felis was also detected in eight (4.6%) dog blood samples. Although the pathogenic potential of these other rickettsial species and their role in RMSF transmission remains unclear, our data on tick burdens in dogs and homes as risk factors for RMSF exposure provide further support to the pivotal need to reduce tick burdens and the numbers of roaming dogs to successfully manage the RMSF epidemic in northern Mexico.

The brown dog tick, Rhipicephalus sanguineus sensu lato (Rh. sanguineus s.l.), is an important vector of Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever (RMSF), in western North America, with the most prominent tick infestations occurring in the Southwestern USA and Northern Mexico. RMSF is a significant public health threat in these regions, including in the state of California. In 2024, the Sacramento-Yolo Mosquito and Vector Control District detected a brown dog tick infestation in a neighborhood in South Sacramento (CA, USA) that encompassed three adjoining properties. This infestation was unusual due to its location farther north than those in most recent reports. In partnership with the Laboratory of Infectious Disease Ecology at the University of California, Davis, a surveillance and abatement program was implemented. This included tick monitoring, residual spraying of acaricide, deployment of tick collars on dogs and bilingual public outreach. The integrated intervention substantially reduced tick populations at the affected site. Both adult and immature stages of Rh. sanguineus s.l. declined following sequential treatments. Sustained suppression and elimination were achieved through continued control and outreach efforts. This localized infestation of Rh. sanguineus s.l. in northern California highlights the potential for range expansion of RMSF vectors and underscores the need for continued surveillance, rapid response and community engagement to mitigate vector-borne disease risks.

We conducted surveillance of mammals to investigate their associations with argasid ticks and tick-borne pathogens. During 2021, a total of 20 wild carnivores and 57 lagomorphs were sampled, and 39 argasid ticks belonging to two species were collected. All mammals and ticks were tested by molecular assays to detect Borrelia and Rickettsia infections. Nine ticks identified as Otobius megnini were collected from two coyotes (Canis latrans) and 30 Alveonasus cooleyi (McIvor 1941) were collected from six bobcats (Lynx rufus) and one rabbit (Sylvilagus auduboni). We detected Rickettsia spp. DNA in 21 of the 27 (77.8%) tested Av. cooleyi and none of the O. megnini. No ticks were PCR-positive for borreliae and all mammals were PCR-negative for both pathogen genera. Phylogenetic analysis based on gltA, htrA, and 16 S rRNA targets revealed that all rickettsiae from Av. cooleyi clustered with ancestral group rickettsiae, likely representing a novel species of possibly endosymbiotic Rickettsia. The significance of Av. cooleyi and the newly identified Rickettsia sp. to the health of wildlife is unknown, and further work is indicated to determine whether they may be relevant to public health or carnivore conservation.

Understanding which detection methods to use is important to endangered species research and management and often requires a balance between costs and benefits. We investigated the efficiency and costs of camera-trapping, live-trapping, and sign surveys (vole feces, clippings, runways) as methods for detection of the endangered Amargosa voles (Microtus californicus scirpensis). Although each method documented the presence of voles, baited camera-trapping was the most sensitive method for detecting voles and provided insights into vole activity and behavior. Although live-trapping had 100% specificity and provided data and access to biological samples that could not be collected through other methods, it had reduced sensitivity (85.2%) compared to camera-traps and incurred potential risk to individual voles. Sign surveys were the least sensitive method (78.9%) and suffered in that some types of sign could not accurately be attributed to species. Additionally, sign surveys could not inform about how recently vole activity had occurred because Amargosa vole feces can persist in the environment for long periods of time and degrade 4.7 times faster in wetter marshes than dryer sites. Sign and fecal surveys are best suited for occupancy and distribution surveys at a coarse time scale (≥1-year intervals) but are likely to have low predictive values in years when vole abundance is low. Cost comparisons indicate the highest per session cost and moderate habitat impact for camera trapping, highest overall cost and highest impact to habitat for live-trapping, and lowest expense and habitat impact for sign surveys but relatively low yield in data quality.

Background: In Lyme-endemic areas, limited research has investigated the risk of tick-borne diseases among frontline workers in fire management. This study aimed to compare the exposure histories to ticks and tick-borne pathogens, knowledge, and prevention practices between individuals engaged in fire-related forest management and those participating in recreational activities within Santa Cruz County, CA, in an area of high risk of tick exposure. Methods: Blood samples from 55 forest workers and 58 members of the public were tested for bacterial DNA of and antibodies to Borrelia burgdorferi, Anaplasma phagocytophilum, and Rickettsia species. In addition, a questionnaire was administered to 54 workers and 84 members of the public to identify gaps in knowledge and prevention practices. Results: Although workers had a higher percentage of positive B. burgdorferi antibodies than the public (5.5% compared with 1.7%), the difference was not statistically significant. Conversely, rickettsial antibodies were more prevalent among the public (17.2% versus 3.6% for workers), but specificity to pathogenic bacteria could not be confirmed. No DNA for the three pathogens or antibodies against A. phagocytophilum were detected. Many workers and members of the public reported tick bites (67.4% of participants), with a notable 11% increase among workers in the odds of being bitten for each additional year spent working in forests. Although workers took greater precautions, significant knowledge and practice gaps were identified among both populations, such as an inability to distinguish tick species from common arthropods (mites, spiders, fleas), overestimating the size of ticks, and inappropriate tick-removal techniques. Conclusion: This study underscores the risk of tick-borne diseases faced by fire management workers in Lyme disease-endemic regions. The findings emphasize the necessity for future studies of Lyme disease within this population, and highlight the urgent need for enhanced training programs to minimize these risks.

A two decades-long epidemic of Rocky Mountain spotted fever in northern Mexico reached the U.S. border city of Tijuana in 2021. Cases were near the city periphery in marginalized areas, some lacking infrastructure such as streets or utilities. We worked in the three census areas where human cases were reported and in 12 additional control Areas Geoestadisticas Basicas. There were dogs, the primary tick host and Rickettsia rickettsii reservoir, in 76% of homes, with 2.2 owned dogs per home on average, approximately equal numbers of roaming dogs were seen, and 46.2% of owned dogs were allowed to roam in the street. Sixty-eight percent of people had heard of Rocky Mountain spotted fever (RMSF), and 35% self-reported tick infestation, including 19% of homes without dogs. Ticks appeared to move among houses of adjacent neighbors. Of 191 examined dogs, 61.8% were tick-infested, with 6-fold increased odds if they were allowed to roam. Although no dogs were Rickettsia polymerase chain reaction-positive, we found one R. rickettsii- and 11 Rickettsia massiliae-infected ticks. The rickettsial IgG seroprevalence by immunofluorescence antibody assay was 76.4%, associated with unhealthy body condition, adults, dogs with >10 ticks, more dogs being seen in the area, and dogs being permitted in the street. Insufficient medical and canine management resources have contributed to a case fatality rate of RMSF that has exceeded 50% in areas. High canine seroprevalence suggests risks to people and dogs; unfortunately, herd immunity is impeded by high turnover in the canine population owing to the birth of puppies and high death rates. Binational One Health workers should monitor disease spread, enact canine population management and tick eradication, and provide prevention, diagnostic, and treatment support.