White-nose syndrome (WNS) continues to compromise hibernating Perimyotis subflavus (tricolored bat) populations as it spreads across their geographic range in North America. Despite the presence of the causative agent, t...White-nose syndrome (WNS) continues to compromise hibernating Perimyotis subflavus (tricolored bat) populations as it spreads across their geographic range in North America. Despite the presence of the causative agent, the fungus Pseudogymnoascus destructans (Pd), in hibernacula, some tricolored bat populations located near the southern extent of their hibernating range remain unaffected by WNS. We propose that disease progression is absent as these hibernacula, mainly highway culverts, are unsuitable for fungal growth because microclimates fall outside the growth limits of the fungus. Thus, this study investigated the role of hibernaculum microclimate in influencing potential Pd growth and subsequently a hibernaculum's capacity to be an environmental reservoir. We collected microclimate data from multiple types of hibernacula (caves, tunnels, and culverts) near the southern extent where Pd and tricolored bat ranges overlap. Analysis revealed differences in microclimates among hibernaculum types, with culverts exhibiting lower humidity over winter, resulting in reduced fungal growth compared with other hibernaculum types. Caves, which maintained optimal humidity for Pd, had the highest predicted cumulative fungal growth (3.53 cm2), more than double the estimated WNS morbidity threshold (1.54 cm2). The tunnel showed a similar pattern, with a maximum growth of 3.16 cm2. In contrast, culverts, with less suitable microclimates, had the lowest predicted fungal growth (1.78 cm2), only 15% above the morbidity threshold. Although previous research primarily focused on temperature, our findings suggest that relative humidity may be a critical factor, particularly near the southern extent of the geographic range of hibernating tricolored bats. These findings emphasize the importance of considering humidity alongside temperature when evaluating hibernaculum susceptibility to fungal invasion and WNS development. Understanding the impact of microclimate on disease dynamics and bat behavior is crucial for developing effective conservation strategies, particularly for tricolored bat populations near the southern extent of susceptible hibernating populations.
We present a case of multicentric lymphoma in a wild chilla fox (Lycalopex griseus) found dead after a dog attack. Mesenteric, bronchial, submandibular, and popliteal lymph nodes and the thymus were affected. Histopathol...We present a case of multicentric lymphoma in a wild chilla fox (Lycalopex griseus) found dead after a dog attack. Mesenteric, bronchial, submandibular, and popliteal lymph nodes and the thymus were affected. Histopathology and immunohistochemistry confirmed a T-cell lymphoma with a histiocytic component.
The swift fox (Vulpes velox) is a small canid species occupying mixed and short-grass prairie ecosystems across western North America. Populations have declined across a large portion of their historical habitat distribu...The swift fox (Vulpes velox) is a small canid species occupying mixed and short-grass prairie ecosystems across western North America. Populations have declined across a large portion of their historical habitat distribution, mainly due to anthropogenic influences. Although some populations appear to be rebounding, the swift fox is classified as a species of greatest conservation need in Wyoming, USA, due to threats from predation, vehicular collisions, and habitat alterations that increase potential contact with humans and domestic animals. This potential contact with other species puts swift foxes at risk from infectious disease transmission, potentially resulting in morbidity or mortality. There are few published studies about disease seroprevalence and presence of parasites from swift foxes within Wyoming. Serum samples (n=103) and fecal samples (n=113) from live swift foxes were opportunistically collected from southeastern Wyoming (2009 and 2020-24) and submitted for testing. Serum samples were assessed for antibodies using an indirect fluorescent antibody test, canine parvovirus (CPV), and virus neutralization tests, canine distemper virus (CDV) and canine adenovirus (CAV). Fecal samples were tested using a standard fecal float and a real-time PCR for Echinococcus spp. and Echinococcus multilocularis. Not all samples could be tested for every assay. Overall, 58 (73%; n=80) foxes were seropositive for CPV, 5 (19%; n=27) for CAV, and 1 (2%; n=53) for CDV. Toxascaris leonina was the most commonly detected (31%; n=44) gastrointestinal parasite, and Echinococcus spp. was detected in one individual (0.9%; n=113). These results reveal previously unidentified levels of seroprevalence and lack of difference between age and sex in this species. Continued exploration and surveillance is needed to assist in determining associated morbidity and mortality and to identify risk factors (e.g., domestic canid, other wild canid comingling) contributing to disease transmission within this population.
Wild Turkeys (Meleagris gallopavo) are an important game species in the USA and have experienced population declines in many areas of their range for >10 yr. Among other hypotheses, increased disease prevalence or novel...Wild Turkeys (Meleagris gallopavo) are an important game species in the USA and have experienced population declines in many areas of their range for >10 yr. Among other hypotheses, increased disease prevalence or novel disease emergence could be contributing factors in Wild Turkey population declines. To address some knowledge gaps and further understand the impacts of two important diseases on Wild Turkey populations, we sought to document the prevalence of histomonosis and lymphoproliferative disease virus (LPDV) in Alabama, USA, and to evaluate the spatial epidemiology of LPDV. We collected hunter-harvested Wild Turkey carcasses and paired observational surveys across Alabama during the 2022 and 2023 spring hunting seasons. During necropsies we collected the ceca, which was frozen and stored at -20 °C, and the spleen, which was stored in 70% ethanol at 20 °C or frozen and stored at -20 °C. We screened cecal walls for Histomonas meleagridis DNA and spleens for LPDV proviral DNA by using quantitative PCR and PCR, respectively. We detected H. meleagridis, the disease-causing protozoan for histomonosis, in 0.7% (3/435) of our samples. We detected LPDV proviral DNA in 88.7% (416/469) of our sample of frozen spleens. Our results suggest that evaluation of the impact of histomonosis on Wild Turkey populations is difficult through active surveillance alone. We detected proviral LPDV DNA in Wild Turkeys from nearly every county sampled in Alabama (53/56 counties); however, a generalized linear mixed model did not reveal a statistically significant relationship between LPDV and land cover type. Our findings demonstrate that LPDV is widely distributed with high rates of prevalence in Alabama. Because the effects of these two diseases and others on Wild Turkey population vital rates have not been well established, further work is warranted.
A radiographic analysis of fractures and/or luxations in raptors was conducted across two wildlife centers, one in Brazil (Center for Medicine and Research in Wild Animals [CEMPAS]; n=106 raptors) and the other in the US...A radiographic analysis of fractures and/or luxations in raptors was conducted across two wildlife centers, one in Brazil (Center for Medicine and Research in Wild Animals [CEMPAS]; n=106 raptors) and the other in the USA (Lindsay Wildlife Experience [LWE]; n=310 raptors), through a data study spanning 7 yr. There were differences between the two centers in which order was most affected. At CEMPAS, Strigiformes accounted for 48.1% of the cases, but at LWE Accipitriformes were most affected (59.4% of cases). The axial skeleton was least affected at both centers, with two cases at CEMPAS and three cases at LWE. Most fractures included a single bone in the appendicular skeleton, accounting for 57.7% at CEMPAS and 61.9% at LWE. In the thoracic limb, the humerus was the most fractured bone at CEMPAS (44/108), whereas the ulna was most commonly fractured at LWE (116/307). In the pelvic limb, the tibiotarsus was the most fractured bone at both centers (23/35 at CEMPAS and 27/80 at LWE). Closed fractures were more frequent in the thoracic and pelvic limbs at both centers. Cases of luxation or subluxation without fractures were less common, with 6.7% at CEMPAS and 7.2% at LWE. The types of fractures and/or luxations identified in this study exhibited several similarities between centers that may be useful in understanding these lesions in raptors and establishing future treatment protocols.
Liver changes in a Bald Eagle (Haliaeetus leucocephalus) were associated with the presence of Myxidium anatidum. The myxozoan parasites were present in bile ducts. The genus and species were determined using an 18S rRNA...Liver changes in a Bald Eagle (Haliaeetus leucocephalus) were associated with the presence of Myxidium anatidum. The myxozoan parasites were present in bile ducts. The genus and species were determined using an 18S rRNA PCR combined with sequencing of the product and a BLASTN search.
In Costa Rica, human-tapir conflicts are increasing, including disease transmission, as Baird's tapirs (Tapirus bairdii) move into human-altered landscapes. We investigated the death of a wild male tapir, identifying a s...In Costa Rica, human-tapir conflicts are increasing, including disease transmission, as Baird's tapirs (Tapirus bairdii) move into human-altered landscapes. We investigated the death of a wild male tapir, identifying a systemic Actinomyces israelii infection. The potential of this pathogen being an emerging health threat for tapir conservation warrants further study.
Joly DO, Berhane Y, Bowman J
… +17 more, Giacinti JA, Goldsmith D, Hentze N, Jones MEB, Jardine CM, Lair S, Leonard EK, Massé A, Mubareka S, Pekarik C, Paré J, Pople N, Pybus MJ, Stevens B, Thompson T, Enns A, Winchester M
Highly pathogenic avian influenza (HPAI) H5Nx virus clade 2.3.4.4b has impacted wild birds and mammals in Canada since late 2021, including at-risk species. We compared detections and conservation status to highlight the...Highly pathogenic avian influenza (HPAI) H5Nx virus clade 2.3.4.4b has impacted wild birds and mammals in Canada since late 2021, including at-risk species. We compared detections and conservation status to highlight the need to integrate disease surveillance with conservation planning when assessing risks and to guide management.
Apicomplexans are endoparasites that infect various animals, including humans, causing significant diseases such as malaria, babesiosis, cryptosporidiosis, neosporosis, and toxoplasmosis. Toxoplasmosis, caused by Toxopla...Apicomplexans are endoparasites that infect various animals, including humans, causing significant diseases such as malaria, babesiosis, cryptosporidiosis, neosporosis, and toxoplasmosis. Toxoplasmosis, caused by Toxoplasma gondii, is a notable public health concern due to its severe effects on pregnant women and immunocompromised individuals. Infection routes include ingestion of oocysts from definitive hosts (felines) or consumption of contaminated meat. Neosporosis, caused by Neospora caninum, causes reproductive issues and significant economic losses in domestic cattle (Bos taurus). Wildlife plays a crucial role in the life cycles of these parasites, with species such as wild boar (Sus scrofa) and axis deer (Axis axis) acting as reservoirs. These ungulate species can affect livestock production systems and public health, particularly in regions like Latin America where they are invasive. Understanding the seroprevalence and transmission dynamics of these parasites in wildlife is vital for developing effective control measures. During 2020-23, 254 wild boar and 90 axis deer blood samples were collected from eight and five departments in Uruguay, respectively. Serologic tests for T. gondii and N. caninum antibodies were conducted using ELISA, with further confirmation of N. caninum antibodies through western blotting. Seroprevalence values of T. gondii were mean 47.7% in wild boars and mean 8.4% in axis deer; whereas N. caninum was more prevalent in axis deer (mean 49.8%) than in wild boars (mean 0.7%). Detection of antibodies against both pathogens in a single individual occurred occasionally. These findings suggest that wild boar and axis deer may play significant roles in maintaining and amplifying T. gondii or N. caninum (or both) infections in Uruguay, and underscore the need for targeted control strategies to mitigate the spread of these pathogens, which have implications for both livestock health and public health.
Over the past 75 years, the Wildlife Disease Association has served as a primary professional resource for the dissemination of scientific information and the generation of seminal contributions on diverse wildlife healt...Over the past 75 years, the Wildlife Disease Association has served as a primary professional resource for the dissemination of scientific information and the generation of seminal contributions on diverse wildlife health issues. Historical examination of the organization's records from 1951 onwards reveals a dynamic evolution in communicative formats, from newsletters, to microfiches and bulletins, to culmination in the current periodical, the Journal of Wildlife Diseases. Using rabies as one major example, to date nearly 300 documents have appeared as Letters to the Editor, short communications, full research articles, engaging perspectives, or expansive reviews. Given the high case fatality, global distribution, broad host susceptibility, and significance to agriculture, human and veterinary medicine, and conservation biology, rabies serves as an ideal One Health exemplar shepherded by the Journal over time. Expansive topics have encompassed individual species case reports and series; sensitive and specific diagnostic methods for enhanced laboratory-based surveillance; disease ecology and control and prevention issues; epidemiological insights; disease emergence; public health engagement; pathogenesis; bio-economics; modeling considerations; host-agent biological traits, serological surveys, and novel vaccinology applied to free-ranging animals; and modern virological techniques. As such, using rabies as a subjective surrogate, the Journal has served as a critical resource, not only to chart the course of progress in the wildlife health field historically, from its rather humble North American origins during the mid-20th century, but also as its continued scientific relevance today in promotion of the transdisciplinary mission of a global professional organization.
Oral rabies vaccination (ORV) has successfully prevented appreciable spread of the raccoon rabies virus variant (RRVV) west of the Appalachian Mountains in the US. However, local and regional elimination of RRVV has been...Oral rabies vaccination (ORV) has successfully prevented appreciable spread of the raccoon rabies virus variant (RRVV) west of the Appalachian Mountains in the US. However, local and regional elimination of RRVV has been challenging, particularly in areas of the eastern US with routine spillover transmission to striped skunk (Mephitis mephitis) populations. We used rabies antibody seroprevalence monitoring data from two ORV baiting strategies, a 75 baits/km2 applied from 2012 to 2013 and a 300 baits/km2 applied from 2014 to 2016, in West Virginia, US, and home range estimates on the basis of data from striped skunks collared with a global positioning system in 2014 and 2015, to identify factors influencing skunk home range size and movements with respect to land cover classes and to compare the efficiency of hypothetical aerial ORV baiting scenarios that may improve bait uptake by skunks and increase post-ORV rabies antibody seroprevalence. When baits were deployed in late August, the mean core and overall skunk home ranges were 0.135 km2 (±0.086 km2 SD) and 0.648 km2 (±0.400 km2 SD), respectively. Skunks preferred, and maintained smaller home ranges in, pasture and had larger home ranges in deciduous-mixed forest. The ORV baiting scenarios that we explored varied in bait density, flight-line spacing between baiting transects, and flight patterns followed to deliver baits. Bait density was the most important factor that we identified; higher bait density increased predicted seroprevalence and possible bait uptake. The crisscross flight pattern compared with the parallel pattern had higher costs without a substantial increase in hypothetical bait uptake. This research provides insight into skunk ecology in a rural area of the eastern US and how various aerial baiting strategies might influence the efficiency and effectiveness of ORV related to skunks.
Sarcoptic mange (SM), caused by the mite Sarcoptes scabiei, is a globally distributed disease affecting a broad range of hosts and posing a potential threat to wildlife. However, its full ecologic impact remains unclear....Sarcoptic mange (SM), caused by the mite Sarcoptes scabiei, is a globally distributed disease affecting a broad range of hosts and posing a potential threat to wildlife. However, its full ecologic impact remains unclear. This study investigates SM occurrence in two native fox species (Lycalopex spp.) in rural central Chile, exploring its association with macrohabitat types, land covers, domestic dogs, and human presence. Fieldwork was conducted across three rural sites (<56 km apart), representing distinct macrohabitats: exotic monoculture tree plantations (Alto Colorado) and two native Mediterranean coastal forest sites, La Estrella (thorn shrubland) and Callihue (sclerophyllous forest). At each site, 10 camera traps were deployed within 100-ha grids for 13 mo. Foxes were detected in all stations, and individuals showing lesions consistent with SM (SM-foxes) were found in 24 of 30 stations, accounting for 329 of 3,140 fox images (10.4% observed prevalence). Domestic dogs were recorded at 28 stations, detected up to 7.9 km from human settlements. In our fine-scale approach, foxes, SM-foxes, and dogs were present across all macrohabitats and land covers, tending to be more abundant in native landscapes. The occurrence of SM was weakly associated with human presence and, to a lesser extent, with domestic dogs, the latter of which nonetheless remain the most plausible original source of SM in the region. In general, SM occurrence, foxes, and domestic dogs were more frequent closer to human settlements and farther from urban areas, reflecting a complex association with human presence. Human settlements were not consistently related to altered macrohabitats such as exotic plantations. Sarcoptes scabiei circulation is probably maintained through both direct and indirect contact, involving occasional spillover from dogs, prey, and infected carcasses. These findings underscore the importance of rural areas as hotspots for dogs-fox interactions and highlight the relevance of understanding fine-scale pathogen dynamics for wildlife conservation.
Human activities, such as habitat fragmentation, have displaced wild birds into urban and agricultural areas, increasing their exposure to enteric pathogens through contaminated food and water. Molting stress further hei...Human activities, such as habitat fragmentation, have displaced wild birds into urban and agricultural areas, increasing their exposure to enteric pathogens through contaminated food and water. Molting stress further heightens their susceptibility to infection. This study examined 1) the presence of Klebsiella pneumoniae, Salmonella enterica serovar Typhimurium, Listeria monocytogenes, and Campylobacter jejuni in fecal samples from Violet-Crowned (Ramosomyia violiceps) and Broad-Billed (Cynanthus latirostris) Hummingbirds across two environments: disturbed forest and urban; 2) potential associations with contamination sources (wastewater, rivers, water bodies, and livestock feces); and 3) the effects of molting. Fecal samples were analyzed using real-time PCR and Bayesian generalized linear mixed models to evaluate five response variables: individual pathogen presence [corresponds to the 3 pathogens (K. pneumoniae, S. enterica, and L. monocytogenes)], combined pathogen presence, and pathogen copresence. Predictors included hummingbird species, molt, environment type, and distance to contamination sources. Of the bacteria, K. pneumoniae exhibited the highest prevalence (46%), followed by S. enterica (9.5%) and L. monocytogenes (7.9%); C. jejuni was not detected. Results indicated that 1) R. violiceps had approximately threefold higher odds of K. pneumoniae presence than C. latirostri and 2) molting individuals had 6.5-fold higher odds of carrying at least one pathogen. Neither environment type nor distance to contamination sources showed significant effects. The high prevalence of K. pneumoniae highlights the urgent need to preserve natural habitats and reduce anthropogenic pressures on wild bird populations. Molting increases susceptibility to gastrointestinal pathogens, while species-specific differences suggest variable resistance mechanisms. These findings underscore the importance of 1) habitat conservation to minimize pathogen exposure, 2) urban green space management with strict hygiene protocols for artificial feeders, and 3) integrated wildlife pathogen surveillance within One Health frameworks.
Wild pig (Sus scrofa) populations are expanding across the USA, raising concerns about the ecologic impacts and role as reservoirs for pathogens of significance to human and animal health. Trypanosoma cruzi, the causativ...Wild pig (Sus scrofa) populations are expanding across the USA, raising concerns about the ecologic impacts and role as reservoirs for pathogens of significance to human and animal health. Trypanosoma cruzi, the causative agent of Chagas disease, is a recognized risk for humans and domestic dogs in the southern USA. Common wildlife reservoirs of T. cruzi include rodents (e.g., Neotoma spp.), raccoons (Procyon lotor), and Virginia opossums (Didelphus virginiana); however, there have been reports of T. cruzi infection in suids, including a domestic pig (Sus scrofa domesticus) in Mexico and three wild pigs in Texas, USA. Our study aimed to better understand the prevalence and distribution of T. cruzi antibodies in wild pigs in the USA. We collected 1,093 serum samples from wild pigs across 12 states in the southern, midwestern, and western regions of the USA, all of which have populations of T. cruzi triatomine vectors. We tested sera for antibodies against T. cruzi using an indirect ELISA and detected an overall apparent prevalence of 14.6% (160/1,093; 95% confidence interval, 12.6-16.9%). Pig sex, age class, month of sampling, and region were not significantly associated with seroprevalence; however, state of origin explained some variation in the data. We demonstrated that wild pigs in the USA were exposed to T. cruzi, highlighting the need for further research elucidating their role in T. cruzi transmission.
North American bison (Bison bison) face significant challenges to their recovery, including disease risks associated with translocation and genetic bottlenecks. This study aimed to achieve a multidisciplinary consensus o...North American bison (Bison bison) face significant challenges to their recovery, including disease risks associated with translocation and genetic bottlenecks. This study aimed to achieve a multidisciplinary consensus on a definition of bison health and to identify key infectious disease concerns linked to bison translocation. A two-round Delphi survey was conducted with 12 of 22 invited experts representing public, tribal, nonprofit, and private sectors. Participants defined bison health as the ability of populations to express natural behaviors, demonstrate resilience to external stressors, and achieve high reproductive output within their environment with minimal intervention. Mycoplasma bovis was identified as a high-priority pathogen due to its severe economic and health impacts. This definition of bison health may be useful as a basis for guiding health monitoring and informing policy as well as identifying key needs of the bison sector.
Drug-induced hypoxemia can occur with the immobilization of free-living moose (Alces alces). We describe the physiologic response of 12 adult females immobilized with thiafentanil and xylazine and exhibiting clinical sig...Drug-induced hypoxemia can occur with the immobilization of free-living moose (Alces alces). We describe the physiologic response of 12 adult females immobilized with thiafentanil and xylazine and exhibiting clinical signs of hypoxemia before (pretreatment) and after (posttreatment) nasal oxygen supplementation (4 L/min) with or without intravenous doxapram.
Baylisascaris procyonis larva migrans is a debilitating and potentially lethal zoonotic, parasitic condition that can infect a large variety of paratenic hosts, including birds and mammals and even humans. The typical pa...Baylisascaris procyonis larva migrans is a debilitating and potentially lethal zoonotic, parasitic condition that can infect a large variety of paratenic hosts, including birds and mammals and even humans. The typical pathway to develop baylisascariasis is to ingest B. procyonis eggs from contaminated feces or through contaminated soil where contaminated fecal matter has decayed. I hypothesized that earthworms (Lumbricus terrestris) living in soils contaminated with B. procyonis eggs from decayed feces of its definitive host, raccoons (Procyon lotor), would incidentally ingest B. procyonis eggs, and in turn, if earthworms were consumed by songbirds, songbirds would become infected with B. procyonis larvae, resulting in baylisascariasis. I placed 100 earthworms in B. procyonis-infused soil and determined that 92% of earthworms had a mean and SE of 7.3±0.4 B. procyonis eggs in their alimentary canals. When B. procyonis-infected earthworms were fed to European Starlings (Sturnus vulgaris), 94% (17/18) of starlings displayed signs of ataxia, torticollis, and paralysis, and 11/18 (61%) died within 22 d of first ingestion of B. procyonis-infected earthworms. White blood cell counts of starlings that ingested B. procyonis-infected earthworms increased nearly threefold, percentage of eosinophils increased 25-fold, and percentage of lymphocytes increased and percentage of heterophils decreased from day 0 to day 12 postingestion. Starlings within the control group remained healthy and displayed normal behaviors. This study highlights an overlooked pathway of baylisascariasis in paratenic hosts, which has potential as a mortality factor for many species within terrestrial ecosystems.
We investigated the prevalence, cyst density, and any associated pathologic changes of Besnoitia spp. in the testis, peritesticular structures, and udder skin of migratory caribou (Rangifer tarandus). Possible risk facto...We investigated the prevalence, cyst density, and any associated pathologic changes of Besnoitia spp. in the testis, peritesticular structures, and udder skin of migratory caribou (Rangifer tarandus). Possible risk factors for infection, cyst density, and inflammation were investigated. Samples from 149 male and 229 female caribou were collected from seven different herds across Canada, Alaska (US), and Greenland, 2007-09. Biopsies were taken from the udder skin in females and from the epididymis, scrotal skin, testis (seminiferous tubules and tunica albuginea), and spermatic cord in males. The cyst density (cysts per square millimeters) of Besnoitia spp. in each tissue, as well as the type of associated inflammation, were determined by histopathologic examination. Individual (age class) and environmental (season and herd) risk factors were investigated for infection, cyst density, and inflammation. Besnoitia spp. cysts were detected in 22.2, 20.4, 11.2, 31.3, 10.4, and 8.0% of the sections of epididymis, scrotal skin, seminiferous tubules, spermatic cord, tunica albuginea, and udder skin, respectively. The median cyst densities varied from 0.07 cysts/mm2 in the seminiferous tubules to 1.02 cysts/mm2 in the udder skin. Age class and season were risk factors for infection, so adults and subadults were more at risk than calves, and infection was more prevalent in the fall months (September to December) relative to other seasons. Subadults, however, demonstrated a higher cyst density compared with adults and calves. During the winter months, a higher risk of inflammation was present compared with other seasons. Overall, the intensity of inflammation was light to mild, and both pericystic and concomitant inflammation were commonly present. Further research should determine whether these parasitic cysts and the associated inflammation influence the functionality of the testis, peritesticular structures, and udder and thus reproduction.
Streptococcus equi ssp. zooepidemicus is a zoonotic bacterium known to cause severe respiratory tract infections in primates, and most documented mortality episodes occur in captivity. Here we report a mass mortality eve...Streptococcus equi ssp. zooepidemicus is a zoonotic bacterium known to cause severe respiratory tract infections in primates, and most documented mortality episodes occur in captivity. Here we report a mass mortality event in a wild population of long-tailed macaques (Macaca fascicularis) inhabiting an urban mosaic habitat in central Bali, Indonesia, and describe the demographic impact and clinical patterns of the outbreak. Mortality was observed in three of the nine social groups that shared overlapping ranges, and the infection spread progressively over time. Clinical signs included lethargy, respiratory distress, and locomotion disorders. Over a 2-mo period during March-May 2022, 170 carcasses were found. Demographic surveys revealed a mortality rate ranging from 16% to 53% among the three affected groups. Adult females and adult males were the most affected age-sex classes, representing 36% and 35% of the carcasses found, respectively. Necropsy findings from four individuals, combined with bacteriological culture, histopathology, qPCR, and 16S rRNA metabarcoding analysis, all suggested Streptococcus equi ssp. zooepidemicus as the most likely causative agent. Similar streptococcal outbreaks had occurred in this population in 1994 and 2012, raising concerns about the recurrent introduction of the bacterium or potential reservoirs either within or outside the macaque population. The recurrence of Streptococcus equi ssp. zooepidemicus outbreaks in this population highlights the impact of lethal bacterial epidemics in wild primates, which remain poorly documented. Strengthening long-term surveillance, including noninvasive serological monitoring, is essential for better understanding infection dynamics and improving conservation strategies.