Tularemia From Veterinary Occupational Exposure.

Tularemia is a disease caused by Francisella tularensis, a highly infectious bacteria that can be transmitted to humans by direct contact with infected animals. Because of the potential for zoonotic transmission of F. tularensis, veterinary occupational risk is a concern. Here, we report on a human case of tularemia in a veterinarian after an accidental needlestick injury during abscess drainage in a sick dog. The veterinarian developed ulceroglandular tularemia requiring hospitalization but fully recovered after abscess drainage and a course of effective antibiotics. To systematically assess veterinary occupational transmission risk of F. tularensis, we conducted a survey of veterinary clinical staff after occupational exposure to animals with confirmed tularemia. We defined a high-risk exposure as direct contact to the infected animal's body fluids or potential aerosol inhalation without use of standard personal protective equipment (PPE). Survey data included information on 20 veterinary occupational exposures to animals with F. tularensis in 4 states. Veterinarians were the clinical staff most often exposed (40%), followed by veterinarian technicians and assistants (30% and 20%, respectively). Exposures to infected cats were most common (80%). Standard PPE was not used during 80% of exposures; a total of 7 exposures were categorized as high risk. Transmission of F. tularensis in the veterinary clinical setting is possible but overall risk is likely low. Veterinary clinical staff should use standard PPE and employ environmental precautions when handling sick animals to minimize risk of tularemia and other zoonotic infections; postexposure prophylaxis should be considered after high-risk exposures to animals with suspected or confirmed F. tularensis infection to prevent tularemia.

Seroprevalence, Blood Chemistry, and Patterns of Canine Parvovirus, Distemper Virus, Plague, and Tularemia in Free-Ranging Coyotes (Canis latrans) in Northern New Mexico, USA.

Wildlife diseases have implications for ecology, conservation, human health, and health of domestic animals. They may impact wildlife health and population dynamics. Exposure rates of coyotes (Canis latrans) to pathogens such as Yersinia pestis, the cause of plague, may reflect prevalence rates in both rodent prey and human populations. We captured coyotes in north-central New Mexico during 2005-2008 and collected blood samples for serologic surveys. We tested for antibodies against canine distemper virus (CDV, Canine morbillivirus), canine parvovirus (CPV, Carnivore protoparvovirus), plague, tularemia (Francisella tularensis), and for canine heartworm (Dirofilaria immitis) antigen. Serum biochemistry variables that fell outside reference ranges were probably related to capture stress. We detected antibodies to parvovirus in 32/32 samples (100%), and to Y. pestis in 26/31 (84%). More than half 19/32 (59%) had antibodies against CDV, and 5/31 (39%) had antibodies against F. tularensis. We did not detect any heartworm antigens (n = 9). Pathogen prevalence was similar between sexes and among the three coyote packs in the study area. Parvovirus exposure appeared to happen early in life, and prevalence of antibodies against CDV increased with increasing age class. Exposure to Y. pestis and F. tularensis occurred across all age classes. The high coyote seroprevalence rates observed for CPV, Y. pestis, and CDV may indicate high prevalence in sympatric vertebrate populations, with implications for regional wildlife conservation as well as risk to humans via zoonotic transmission.

Tularemia - a re-emerging disease with growing concern.

Tularemia caused by Gram-negative, coccobacillus bacterium, Francisella tularensis, is a highly infectious zoonotic disease. Human cases have been reported mainly from the United States, Nordic countries like Sweden and Finland, and some European and Asian countries. Naturally, the disease occurs in several vertebrates, particularly lagomorphs. Type A (subspecies tularensis) is more virulent and causes disease mainly in North America; type B (subspecies holarctica) is widespread, while subspecies mediasiatica is present in central Asia. F. tularensis is a possible bioweapon due to its lethality, low infectious dosage, and aerosol transmission. Small mammals like rabbits, hares, and muskrats are primary sources of human infections, but true reservoir of F. tularensis is unknown. Vector-borne tularemia primarily involves ticks and mosquitoes. The bacterial subspecies involved and mode of transmission determine the clinical picture. Early signs are flu-like illnesses that may evolve into different clinical forms of tularemia that may or may not include lymphadenopathy. Ulcero-glandular and glandular forms are acquired by arthropod bite or handling of infected animals, oculo-glandular form as a result of conjunctival infection, and oro-pharyngeal form by intake of contaminated food or water. Pulmonary form appears after inhalation of bacteria. Typhoidal form may occur after infection via different routes. Human-to-human transmission has not been known. Diagnosis can be achieved by serology, bacterial culture, and molecular methods. Treatment for tularemia typically entails use of quinolones, tetracyclines, or aminoglycosides. Preventive measures are necessary to avoid infection although difficult to implement. Research is underway for the development of effective live attenuated and subunit vaccines.

Population Density of European Hare Predicts Risk of Tularemia Infection, Czech Republic, 2006-2022.

Background: Over 200 different animal species are susceptible to infection by tularemia, highly infectious disease caused by Francisella tularensis. Hares (Lepus sp.) and small rodents, such as common vole (Microtus arvalis), have been acknowledged as the most significant sources of human tularemia infection in most European countries. Our objective was to verify ability of these species in predicting incidence of human tularemia in a Central European country, the Czech Republic. Materials and Methods: We used 17 years of data on densities of European hare (Lepus europaeus) and common vole, and climate variability to test effects of these factors on temporal dynamics of tularemia incidence. The data were obtained from annual reports available from online e-repositories. Results: The analysis showed that 33% of the yearly variation in human tularemia incidence was explained solely by the abundance of European hare in the Czech Republic during 2007-2022. Density of common vole and North Atlantic Oscillation index, a measure of climate variability, did not significantly explain tularemia incidence. While hare population declined severely during 1993-2022, we did not detect any clear accompanied decrease in the prevalence of tularemia in humans and hares. Conclusion: Contrary to expectations, only hares proved capable in predicting yearly dynamics in human tularemia incidence in the Czech Republic. We call for continued monitoring of infection rates in hares and advocate the use of hunter estimates of hare abundance as a cheap and effective means of predicting the risk of tularemia.

Gamasid Ticks as Vectors of Tularemia in the Southeast of Armenia.

Background: The natural environment of southeastern Armenia, which includes the Syunik and Vayots Dzor regions, provides a high biodiversity of flora and fauna, including ectoparasites. Currently, the fauna and ecology of gamasid ticks and their role in the circulation of tularemia in this area are unclear and incomplete. To better understand the persistence of tularemia in Armenia, an assessment of specific hosts and their vectors is needed to evaluate their role in perpetuating tularemia. Materials and Methods: Utilizing data and samples collected from 1970 to 2020, we have evaluated the species composition of gamasid ticks found on the common vole and in their nests and burrows, and identified the presence of tularemia over time. We evaluated five different geographical landscapes: semidesert, dry mountain steppe, mountain steppe, mountain forest, and high mountain in the communities and open areas of Kapan, Goris, Sisian, Meghri, and Jermuk. Results: We determined the density of gamasid ticks in southeastern Armenia over the 50-year period and isolated 20 cultures of tularemia in 12 separate years. Conclusions: It is important to regularly monitor gamasid ticks in southeastern Armenia to clarify the risk factors for the occurrence of tularemia epizootics, among both carriers and vectors, to better understand the full epidemiological picture.

Tracking the footsteps of Francisella tularensis: Bacteriological and serological monitoring in epidemic areas in Ankara.

The study aimed to detect Francisella tularensis (F. tularensis) in water samples and to investigate the seroreactivity of sheep to tularemia in endemic areas where human tularemia cases have been reported in Ankara, Turkey. For the isolation of F. tularensis, 50 water samples were collected from rural areas of 5 regions of Ankara (Turkey) and selectively cultured on Francis medium supplemented with 8-9 % sheep blood and antibiotics (100 IU/ml penicillin G, 100 mg/L cycloheximide, 80,000 U/L polymixin B). No F. tularensis isolate was cultivated from the water samples. To determine the seroreactivity of sheep to tularemia, 1006 sheep blood samples were collected from the regions, where human tularemia is endemic. A microagglutination test (MAT) identified significant antibody titers, ranging from 1/20-1/640 in 181 (17.99 %) of the investigated sheep sera. Further investigation is required in order to evaluate and confirm a possible epidemiologic relationship between human outbreaks and probable role of sheep or other sources.

Francisella tularensis PCR detection in Cape hares (Lepus capensis) and wild rabbits (Oryctolagus cuniculus) in Algeria.

Tularemia is a zoonosis caused by the bacterium Francisella tularensis. Leporids are primary sources of human infections in the northern hemisphere. Africa is classically considered free of tularemia, but recent data indicate that this dogma might be wrong. We assessed the presence of this disease in wild leporids in Algeria. Between 2014 and 2018, we collected 74 leporids carcasses from spontaneously dead or hunted animals. Francisella tularensis DNA was detected by specific real-time PCR tests in 7/36 (19.44%) Cape hares (Lepus capensis) and 5/38 (13.15%) wild rabbits (Oryctolagus cuniculus). Known tularemia arthropod vectors infested half of the PCR-positive animals. At necropsy, F. tularensis-infected animals presented with an enlarged spleen (n = 12), enlarged adrenal glands (12), liver discoloration (12), hemorrhages (11), and pneumonia (11). Immunohistological examination of liver tissue from one animal was compatible with the presence of F. tularensis. Our study demonstrates the existence of tularemia in lagomorphs in Algeria. It should encourage investigations to detect this disease among the human population of this country.

Molecular detection of Francisella tularensis in small ruminants and their ticks in western Iran.

Francisella tularensis is the causative agent of tularemia an infectious zoonotic disease. We attempted the molecular detecting of F. tularensis in small ruminants and ticks attached to these animals in Kurdistan province (the west of Iran). In this study, 250 blood and 244 tick samples were collected from sheep and goats and were tested for F. tularensis ISFtu2 gene detection using the Real Time-TaqMan PCR method. The collected ticks were morphologically classified as Dermacentor marginatus (67.2%), Rhipicephalus turanicus (12.30%), Rhipicephalus sanguineus (10.66%), and Haemaphysalis concinna (9.83%). No positive F. tularensis were identified in animal blood samples. F. tularensis was detected in 2 (0.82%) ticks samples. Positive samples were identified as F. tularensis subsp. holarctica and collected from D. marginatus ticks and Divandareh county. In this study, the presence of F. tularensis in ticks of Kurdistan province was confirmed, the possible role of ticks in the transmission to livestock and human through tick bites in this region should be considered.

Assessment of Zoonotic Risk following Diagnosis of Canine Tularemia in a Veterinary Medical Teaching Hospital.

Tularemia is a rare zoonotic disease found worldwide. The agent responsible for disease, Francisella tularensis, is one of the most highly infectious pathogens known, one that is capable of causing life-threatening illness with inhalation of <50 organisms. High infectivity explains concerns of its use in bioterrorism. This case describes a 4-year-old male neutered Australian shepherd presented for evaluation of hyporexia and fever. Physical examination revealed marked enlargement of the right superficial cervical lymph node. Tularemia lymphadenitis was diagnosed by lymph node aspiration cytology and culture. Public health officials were advised of the isolation of this zoonotic pathogen, and contact tracing was instituted. Seven individuals associated with the aspiration event were screened for tularemia and treated with prophylactic ciprofloxacin. All were negative, and none became sick. The dog was treated with doxycycline for 3 weeks, and clinical signs and physical examination abnormalities were resolved fully. The owner, a solid organ transplant recipient, was also screened for disease and received prophylactic doxycycline due to a history of shared exposure. The owner remained well throughout the course of his dog's disease and has heightened awareness of potential zoonoses. This case highlights the importance of animals as a sentinel for human health threats and for coordination of human and veterinary care.

Sensitivity of an international notification system for wildlife diseases: A case study using the OIE-WAHIS data on tularemia.

The World Organization for Animal Health (OIE) has recently developed a Wildlife Health Framework to respond to the need of members to manage the risk from emerging diseases at the animal-human-ecosystem interface. One of its objectives is to improve surveillance systems, early detection and notification of wildlife diseases. Members share information on disease occurrence by reporting through the OIE World Animal Health Information System (OIE-WAHIS-formerly known as 'WAHIS'). To evaluate the capacity of a surveillance system to detect disease events, it is important to quantify the gap between all known events and those officially notified to the OIE. This study used capture-recapture analysis to estimate the sensitivity of the OIE-WAHIS system for a OIE-listed wildlife disease by comparing information from publicly available sources to identify undetected events. This article presents a case study of the occurrence of tularemia in lagomorphs among selected North American and European countries during the period 2014-2019. First, an analysis using three data sources (OIE-WAHIS, ProMED, WHO-EIOS [Epidemic Intelligence from Open Sources]) was conducted. Subsequent analysis then explored the model integrating information from a fourth source (scientific literature collected in PubMed). Two models were built to evaluate both the sensitivity of the OIE-WAHIS using media reports (ProMED and WHO-EIOS), which is likely to represent current closer to real-time events, and published scientific data, which is more useful for retrospective analysis. Using the three-source approach, the predicted number of tularemia events was 93 (95% CI: 75-114), with an OIE-WAHIS sensitivity of 90%. In the four-source approach, the number of predicted events increased to 120 (95% CI: 99-143), dropping the sensitivity of the OIE-WAHIS to 70%. The results indicate a good sensitivity of the OIE-WAHIS system using the three-source approach, but lower sensitivity when including information from the scientific literature. Further analysis should be undertaken to identify diseases and regions for which international reporting presents a low sensitivity. This will enable evaluation and prioritization of underreported OIE-listed wildlife diseases and identify areas of focus as part of the Wildlife Health Framework. This study also highlights the need for stronger collaborations between academia and National Veterinary Services to enhance surveillance systems for notifiable diseases.

The monitoring of Francisella tularensis in surface water of East Azerbaijan province, Iran.

BACKGROUND: Francisella tularensis could be disseminated through arthropod bites and exposure to infected animals, water, and aerosols. Water sources that are contaminated with rodent excrement could be a source of contamination; therefore, an analysis of water samples is an appropriate method to investigate the routes of dissemination. Since an outbreak occurred in one of the villages in East Azerbaijan. The current study aimed to investigate the Francisella isolation in the different water samples from East Azerbaijan, Iran. Sampling was carried out in East Azerbaijan province. Forty-six specimens of surface water were collected. Filtration, culture, and inoculation of the water sample into NMRI (Naval Medical Research Institute) inbreed mice were performed. DNA was extracted from filtered water samples, different organs of inoculated mice, and bacterial isolates and was tested by TaqMan real-time PCR by targeting ISFtu2 and fopA genes. Despite the unsuccessfulness in isolation of F. tularensis, molecular test results indicate the presence of bacteria in surface water. The highest rate of F. tularensis (ten from 46 water samples, 21.7%) was detected from injected mice based on molecular methods. Despite the high efforts of researchers to isolate Francisella spp. in Iran, in recent years, and also the evidence that shows the presence of this bacterium in different parts of the country, the culture was not successful again in this study and the molecular method still is recommended to identify the possible sources of Francisella spp.

Epidemiological investigation of a tularaemia outbreak after a hare hunt in Bavaria, Germany, 2018.

In November 2018, a tularaemia outbreak occurred in Bavaria, Germany, among participants of a hare hunt and butchery employees handling the hares. We conducted an epidemiological outbreak investigation, including a retrospective cohort study among hunting participants, to identify likely transmission routes and activities associated with infection. Twelve of 41 participants were antibody-positive for Francisella (F.) tularensis (attack rate: 29%). Cases reported influenza-like symptoms (n = 11), lymphadenopathy (n = 1) and conjunctivitis (n = 1). Infection only occurred in those hunting participants present while hares were processed, while risk of infection was highest when directly involved (RR = 10.0; 95%CI: 2.6-392). F. tularensis was isolated from 1/4 hares. Only two individuals reported using some of the recommended personal protective equipment (PPE). Occurrence of mainly non-specific symptoms, likely due to early treatment, was not indicative of a specific transmission route. Transmissions via direct (skin/mucosa) contact and by inhalation of contaminated aerosols seem plausible. Promoting and increasing appropriate use of PPE among people processing hares is crucial to prevent future outbreaks.

Detection and Genotyping of Francisella tularensis in Animal Hosts and Vectors from Six Different Natural Landscape Areas, Gansu Province, China.

OBJECTIVE: Tularemia, also known as hare fever, is caused by the bacterium Francisella tularensis (F. tularensis) transmitted through diseased wild animals, blood sucking insects, or contaminated water or food, which is distributed worldwide. The purpose of this study was to investigate F. tularensis infection in animal hosts and vectors from six different natural landscape areas in Gansu Province and to identify the genotypes of the detected F. tularensis. METHODS: Rodents were captured by snap traps, and ticks were collected by dragging a cloth over the vegetation or from domestic animals. After species identification, DNA was isolated from the captured animals and detected by nested PCR assays targeting the F. tularensis fopA gene. The positive samples were further amplified to discriminate the species, and another two short-sequence tandem repeat regions (SSTR) were amplified to identify their genotypes. All positive fragments were sequenced and analyzed by ClustalX (5.0) and DNAClub software. RESULTS: A total of 407 rodents of 12 species were captured, among which six rodent species were positive for F. tularensis, with an overall prevalence of 3.93%. The geographical difference in infection rate was statistically significant. At the SSTR9 locus, there were 7 genotypes among positive rodent samples. A total of 1864 ticks were tested for evidence of tularemia by nested PCR assays, 69 of which were positive, with an average positive rate of 3.70% for F. tularensis in ticks. The positive rates were significantly different among different regions. Seven genotypes were identified at the SSTR9 locus, one of which seemed dominant in positive tick samples. All positive samples had the same genotype at the SSTR16 locus. CONCLUSION: There is natural infection of F. tularensis among animal vectors and hosts in Gansu Province, with diverse genotypes.

Natural Infection of a European Red Squirrel (Sciurus vulgaris) with Francisella tularensis subsp. Holarctica.

Postmortem examination and immunohistochemical and bacteriologic analyses on a free-ranging European red squirrel (Sciurus vulgaris) revealed a systemic infection with Francisella tularensis. Genome sequencing and single-nucleotide polymorphism analysis were consistent with F. tularensis subs. holarctica clade B.45. Tularemia has not previously been reported in this species.

Characterization of Tularemia Cases in Slovenia with Multiple-Locus Variable-Number Tandem Repeat Analysis.

Francisella tularensis is the etiologic agent of tularemia, a bacterial zoonotic disease. The genome of F. tularensis shows a recent evolutionary change, especially in reservoirs. Variable number of tandem repeats (VNTR) is described as a high-speed molecular clock and can thus be used as a high-resolution typing system. The main objective of our study was to investigate the molecular diversity of F. tularensis strains and reveal possible sources of infection. Using real-time PCR targeting the ISFtu2 region, we successfully amplified targeted DNA in 13/31 Slovenian patients with a clinical diagnosis of tularemia, and with PCR targeting the fopA gene, we obtained 11/13 PCR products. Sequencing revealed that all samples were identified as F. tularensis subsp. holarctica. We successfully obtained one F. tularensis isolate from a lymph node aspirate by culture on chocolate agar. Our isolate was clustered into major clade B12 (subclade B43). We optimized VNTR typing to be used directly on clinical samples. Multiple-locus VNTR analysis (MLVA) revealed five unique MLVA types; 45.5% samples had the same MLVA type, another 27.3% shared a different MLVA type, and each of the remaining had a unique MLVA type. Most samples differed at only two VNTR markers (Ft-M03 and Ft-M06). Additionally, we investigated samples from small mammals (n = 532) and Ixodes ricinus ticks (n = 232) captured in the same geographical area in which patients with tularemia were found. No F. tularensis DNA was detected in samples of small mammals or I. ricinus ticks. The diversity of MLVA types in Slovenia was high, despite the small region, but most of the samples from the same region shared the same MLVA type. Our results suggest that MLVA is a useful tool for quick molecular characterization of F. tularensis directly from patient samples, especially when investigating geographically localized outbreaks.

Fatal toxoplasmosis in wild European brown hares (Lepus europaeus) in tularaemia endemic areas of the Czech Republic: Poses risk of infection for humans?

Toxoplasma gondii may cause fatal infection in European brown hares (Lepus europaeus). However, the role of this parasite in terms of mortality rate in tularaemia endemic areas, amount of parasites in affected organs and circulating genotypes, is still unknown. In total, 36 hares (killed or found dead) were submitted for pathomorphological examination as a part of the national tularaemia and brucellosis monitoring. Tissue samples (lung, heart, liver, spleen and kidney) were tested by quantitative real-time PCR targeting 529 bp region of T. gondii. Genotyping was performed by a 15 microsatellite markers method in a single multiplex PCR assay. The same tissues of hares were simultaneously used for the bacteriological cultivation. Toxoplasma gondii was detected by qPCR in the tissues of two hares. Spleen and lungs of one infected hare have been found harbouring up to ~7 millions of T. gondii parasites per gram of tissue. Both positive samples were characterized as T. gondii type II, one archetypal clonal type II and the other one a type II variant (W35 = 244). Bacteria Francisella tularensis was proved in pooled samples of three hares but without coinfection with T. gondii; all hares were negative for Brucella suis. Toxoplasma gondii has significant impact on mortality of European brown hares in tularaemia endemic areas and parasite load within the animal tissues may present high risk of human infection.

Francisella tularensis survey among ranchers and livestock in western Iran.

Tularemia is a zoonotic disease that transmitted to humans and domestic animals by wildlife, especially rodents. There are some evidences of the circulation of F. tularensis in rodents, livestock, human populations, and surface waters in western parts of Iran. In this study, we investigated the exposure of livestock and ranchers to F. tularensis in the endemic regions of western Iran. Blood samples were collected from 289 sheep, 103 cattle, and 51 ranchers in 2018. Animal sera were tested by standard tube agglutination method. The specific IgGs against F. tularensis were evaluated by ELISA in human sera. Moreover, the extracted DNAs from 50 sheep spleen samples were evaluated using TaqMan real-time PCR for the presence of ISFtu2 and FopA genes. All animal sera and spleen samples were negative for tularemia. Of the 51 human samples, two samples were seropositive and one sample showed a borderline status for tularemia. Serologic evidence of F. tularensis in the ranchers but negative results in the livestock indicates different transmission routes in human populations and domestic animals in western Iran. Therefore, drinking contaminated water, contact to wildlife or rodents and arthropod bite should be considered as probable routes in the suspicious areas.

First European report of Francisella tularensis subsp. holarctica isolation from a domestic cat.

Francisella tularensis subsp. holarctica is a select agent causing life-threatening tularemia. It has been isolated from humans and animals, mainly lagomorphs and rodents, rarely other wild carnivore species. Increasing numbers of human tularemia cases have been reported during the last 5 years in Switzerland. Here we report the first isolation of Francisella tularensis subsp. holarctica from a domestic cat in Europe and compare its genome sequence with other Swiss isolates. The cat isolate shows a close phylogenetic relationship with a contemporary hare isolate from close geographic proximity, indicating a possible epidemiological link.

VOC fingerprints: metabolomic signatures of biothreat agents with and without antibiotic resistance.

Category A and B biothreat agents are deemed to be of great concern by the US Centers for Disease Control and Prevention (CDC) and include the bacteria Francisella tularensis, Yersinia pestis, Burkholderia mallei, and Brucella species. Underscored by the impact of the 2020 SARS-CoV-2 outbreak, 2016 Zika pandemic, 2014 Ebola outbreak, 2001 anthrax letter attacks, and 1984 Rajneeshee Salmonella attacks, the threat of future epidemics/pandemics and/or terrorist/criminal use of pathogenic organisms warrants continued exploration and development of both classic and alternative methods of detecting biothreat agents. Volatile organic compounds (VOCs) comprise a large and highly diverse group of carbon-based molecules, generally related by their volatility at ambient temperature. Recently, the diagnostic potential of VOCs has been realized, as correlations between the microbial VOC metabolome and specific bacterial pathogens have been identified. Herein, we describe the use of microbial VOC profiles as fingerprints for the identification of biothreat-relevant microbes, and for differentiating between a kanamycin susceptible and resistant strain. Additionally, we demonstrate microbial VOC profiling using a rapid-throughput VOC metabolomics method we refer to as 'simultaneous multifiber headspace solid-phase microextraction' (simulti-hSPME). Finally, through VOC analysis, we illustrate a rapid non-invasive approach to the diagnosis of BALB/c mice infected with either F. tularensis SCHU S4 or Y. pestis CO92.

Selective Predation by Owls on Infected Bank Voles (Myodes glareolus) as a Possible Sentinel of Tularemia Outbreaks.

Tularemia is a widely spread zoonotic disease in the northern hemisphere, caused by the bacterium Francisella tularensis. In humans, tularemia is an acute febrile illness with incidence peaks in late summer to early autumn of outbreak years, but there is no early warning system in place that can reduce the impact of disease by providing timely risk information. In this study, we revisit previously unpublished data on F. tularensis in water, sediment, soil, and small mammals from 1984 in northern Sweden. In addition, we used human case data from the national surveillance system for tularemia in the same year. In the environmental and small mammal material, bank vole (Myodes glareolus) samples from urine and bladder were the only samples that tested positive for F. tularensis. The prevalence of F. tularensis among trapped bank voles was 13.5%, although all six bank voles that were retrieved from owl nest boxes in early May tested positive. Forty-two human tularemia cases were reported from August to December in 1984. Based on these results, we encourage investigating the potential role of tularemia-infected bank voles retrieved from owl nest boxes in spring as an early warning for outbreaks of tularemia among humans in summer and autumn of the same year.