Targeting Tularemia: Clinical, Laboratory, and Treatment Outcomes From an 11-year Retrospective Observational Cohort in Northern Sweden.

BACKGROUND: Tularemia is an important reemerging disease with a multimodal transmission pattern. Treatment outcomes of current recommended antibiotic regimens (including ciprofloxacin and doxycycline) remain unclear. In this retrospective cohort study, we report clinical, laboratory, geographical, and treatment outcomes of laboratory-confirmed tularemia cases over an 11-year period in Northern Sweden. METHODS: Data from reported tularemia cases (aged >10 years at time of study) in Norrbotten county between 2011 and 2021 were collected through review of electronic medical records and participant questionnaires; 415 of 784 accepted participation (52.9%). Of these, 327 were laboratory-confirmed cases (serology and/or polymerase chain reaction). A multivariable logistic regression model was used to investigate variables associated with retreatment. RESULTS: Median age of participants was 54 years (interquartile range [IQR], 41.5-65) and 49.2% were female. Although ulceroglandular tularemia was the predominant form (n = 215, 65.7%), there were several cases of pulmonary tularemia (n = 40; 12.2%). Inflammatory markers were largely nonspecific, with monocytosis frequently observed (n = 36/75; 48%). Tularemia was often misdiagnosed on presentation (n = 158, 48.3%), with 65 (19.9%) receiving initial inappropriate antibiotics and 102 (31.2%) retreated. Persistent lymphadenopathy was infrequent (n = 22, 6.7%), with 10 undergoing surgical interventions. In multivariable analysis of variables associated with retreatment, we highlight differences in time until receiving appropriate antibiotics (8 [IQR, 3.25-20.75] vs 7 [IQR, 4-11.25] days; adjusted P = .076), and doxycycline-based treatment regimen (vs ciprofloxacin; adjusted P = .084), although this was not significant after correction for multiple comparisons. CONCLUSIONS: We comprehensively summarize clinical, laboratory, and treatment outcomes of type B tularemia. Targeting tularemia requires clinical awareness, early diagnosis, and timely commencement of treatment for an appropriate duration.

Investigation of a Human Case of Francisella tularensis Infection, United Kingdom, 2023.

Tularemia, caused by Francisella tularensis, is not known to occur in the United Kingdom. We report a case of tularemia diagnosed in July 2023 in a UK patient with no travel in the 6 weeks before symptom onset. We describe the subsequent multiagency investigation into possible routes of acquisition.

Water and mosquitoes as key components of the infective cycle of Francisella tularensis in Europe: a review.

Francisella tularensis is the pathogen of tularemia, a zoonotic disease that have a broad range of hosts. Its epidemiology is related to aquatic environments, particularly in the subspecies holarctica. In this review, we explore the role of water and mosquitoes in the epidemiology of Francisella in Europe. F. tularensis epidemiology has been linked to natural waters, where its persistence has been associated with biofilm and amebas. In Sweden and Finland, the European countries where most human cases have been reported, mosquito bites are a main route of transmission. F. tularensis is present in other European countries, but to date positive mosquitoes have not been found. Biofilm and amebas are potential sources of Francisella for mosquito larvae, however, mosquito vector capacity has not been demonstrated experimentally, with the need to be studied using local species to uncover a potential transmission adaptation. Transstadial, for persistence through life stages, and mechanical transmission, suggesting contaminated media as a source for infection, have been studied experimentally for mosquitoes, but their natural occurrence needs to be evaluated. It is important to clear up the role of different local mosquito species in the epidemiology of F. tularensis and their importance in all areas where tularemia is present.

Thoracic manifestations of tularaemia: a case series.

BACKGROUND: Tularaemia is a zoonotic disease caused by Francisella tularensis, a highly virulent bacterium that affects humans and small wild animals. It is transmitted through direct contact with infected animals or indirectly through contaminated soil, water or arthropod bites (e.g. ticks). Primary thoracic manifestations of tularaemia are infrequent and, therefore, a diagnostic challenge for clinicians. METHODS: We report six tularaemia cases with exclusively thoracic involvement diagnosed in a clinic for pulmonary diseases in Bavaria between 10/2020 and 02/2022. RESULTS: All patients lived or were active in rural areas, four reported a recent tick bite. All patients presented with thoracic lymphadenopathy and pulmonary tumours or consolidations; all underwent bronchoscopy with EBUS-TBNA of lymph nodes, three lung biopsies as well. Five patients showed inflammatory changes in the endobronchial mucosa. The main histological findings were necrotic epithelioid granulomas with remarkable granulocyte infiltration. All cases were identified by positive serology, five by PCR (here identification of F.t. ssp. Holarctica) from biopsy as well. As first-line therapy, oral ciprofloxacin was given (5/6); in 2/6 cases, a combination of quinolone-rifampicin was given. CONCLUSIONS: Pulmonary tularaemia may occur after tick bites and without extrathoracic manifestations. In patients who present with thoracic lymphadenopathy and pulmonary consolidations and who are exposed to increased outdoor activities, tularaemia should be included in the diagnostic pathway. Histologically, the presence of neutrophil-granulocyte infiltrations might help to distinguish tularaemia from other granulomatous infections, e.g. tuberculosis. The combination of quinolone-rifampicin rather than i.v. gentamicin reduced length of hospital stay in two patients.

Successful treatment of glandular tularemia with azithromycin in a pregnant woman in Austria.

Treatment of tularemia during pregnancy is challenging due to toxicity of standard treatment regimens. Here, we report a 31-year-old woman with glandular tularemia who was successfully treated with intravenous azithromycin. Follow-up examinations over a 6-month period showed a sustained response to treatment. She later gave birth to a healthy child.

Tick abundance and infection with three zoonotic bacteria are heterogeneous in a Belgian peri-urban forest.

Ixodes ricinus is a vector of several pathogens of public health interest. While forests are the primary habitat for I. ricinus, its abundance and infection prevalence are expected to vary within forest stands. This study assesses the spatio-temporal variations in tick abundance and infection prevalence with three pathogens in and around a peri-urban forest where human exposure is high. Ticks were sampled multiple times in 2016 and 2018 in multiple locations with a diversity of undergrowth, using the consecutive drags method. Three zoonotic pathogens were screened for, Borrelia burgdorferi s.l., Coxiella burnetii, and Francisella tularensis. The influence of season, type of site and micro-environmental factors on tick abundance were assessed with negative binomial generalized linear mixed-effects models. We collected 1642 nymphs and 181 adult ticks. Ticks were most abundant in the spring, in warmer temperatures, and where undergrowth was higher. Sites with vegetation unaffected by human presence had higher abundance of ticks. Forest undergrowth type and height were significant predictors of the level of tick abundance in a forest. The consecutive drags method is expected to provide more precise estimates of tick abundance, presumably through more varied contacts with foliage. Borrelia burgdorferi s.l. prevalence was estimated from pooled ticks at 5.33%, C. burnetii was detected in six pools and F. tularensis was not detected. Borrelia afzelii was the dominant B. burgdorferi genospecies. Tick abundance and B. burgdorferi s.l. infection prevalence were lower than other estimates in Belgian forests.

Tularemia: a case series from an endemic area in Hajnówka County, Norteast Poland. / Opis serii przypadków tularemii z obszaru endemicznego na terenie powiatu hajnowskiego.

BACKGROUND: Tularemia is a zoonotic disease caused by the bacterium Francisella tularensis. It may manifest itself in various clinical forms, but in Poland the ulcerative-glandular or glandular forms of tularemia predominate. One of the routes of infection with F. tularensis is through a tick or insect bite. A patient may show no symptoms or report flu-like symptoms and painful lumps adjacent to the bite site. The differential diagnosis of localized lymphadenopathy accompanied by flu-like symptoms should include tularemia, especially in endemic areas. Lymphadenitis usually requires surgical intervention and is often unsuccessfully treated with beta-lactam antibiotics before the diagnosis of tularemia is established. OBJECTIVE: The aim of the study was to analyze and present the epidemiology and clinical presentation of tularemia in a highly endemic area, in which ticks are an important vector of F. tularensis. MATERIAL AND METHODS: We have analyzed epidemiological and medical reports on the confirmed tularemia cases from Hajnówka County in 2014-2022. We describe three patients from the specific endemic area who were diagnosed with granular tularemia in 2022. RESULTS: We have found high local exposition to Francisella tularensis infection in the Narewka community, generally consistent with the seasonality of tick activity and human activity outdoors. CONCLUSIONS: The medical practitioner in such endemic areas must be aware that tularemia should be considered when diagnosing of flu-like symptoms accompanied by lymphadenopathy in patients bitten by ticks or insects in the summer and early autumn months. Early diagnosis and targeted antibiotic therapy are the basis for effective treatment of tularemia.

Francisella tularensis human infections in a village of northwest Iran.

BACKGROUND: Recent seroepidemiological studies have suggested that tularemia could be an endemic bacterial zoonosis in Iran. METHODS: From January 2016 to June 2018, disease cases characterized by fever, cervical lymphadenopathy and ocular involvement were reported in Youzband Village of Kaleybar County, in the East Azerbaijan Province, northwestern Iran. Diagnostic tests included Francisella tularensis serology (including tube agglutination test and ELISA), PCR, and culture. RESULTS: Among 11 examined case-patients, the tularemia tube agglutination test was positive in ten and borderline in one. PCR detected the F. tularensis ISFtu2 elements and fopA gene in one rodent and a spring water sample from the same geographic area. CONCLUSIONS: Based on the clinical manifestations of the disease suggesting an oropharyngeal form of tularemia, serology results in case patients, and F. tularensis detection in the local fauna and aquatic environment, the water supply of the village was the likely source of the tularemia outbreak. Intervention such as dredging and chlorination of the main water storage tank of the village and training of villagers and health care workers in preventive measures and treatment of the illness helped control the infection.

Reevaluating limits of detection of 12 lateral flow immunoassays for the detection of Yersinia pestis, Francisella tularensis, and Bacillus anthracis spores using viable risk group-3 strains.

AIM: Rapid detection of biological agents in biodefense is critical for operational, tactical and strategic levels as well as for medical countermeasures. Yersinia pestis, Francisella tularensis, and Bacillus anthracis are high priority agents of biological warfare or bioterrorism and many response forces use lateral flow assays (LFAs) for their detection. Several companies produce these assays, which offer results in short time and are easy to use. Despite their importance, only few publications on the limits of detection (LOD) for LFAs are available. Most of these studies used inactivated bacteria or risk group-2 strains. As the inactivation process in previous studies might have affected the tests' performances, it was our aim in this study to determine and compare the LOD of several commercially available LFAs using viable risk group-3 strains. METHODS AND RESULTS: Lateral flow assays from four different companies for the detection of following bacteria were evaluated: Y. pestis, F. tularensis and B. anthracis spores. Two independent quantification methods for each target organism were applied, in order to ensure high quantification accuracy. LODs varied greatly between tests and organisms and ranged between 104 for Y. pestis-tests and as high as >109 for one B. anthracis-test. CONCLUSION: This work precisely determined the LODs of LFAs from four commercial suppliers. The herein determined LODs differed from results of previous studies. This illustrates the need for using accurately quantified viable risk group 3-strains for determining such LODs. SIGNIFICANCE AND IMPACT OF THE STUDY: Our work bridges an important knowledge gap with regard to LFA LOD. The LODs determined in this study will facilitate better assessment of LFA-results. They illustrate that a negative LFA result is not suited to exclude the presence of the respective agent in the analyzed sample.

Early detection of viable Francisella tularensis in environmental matrices by culture-based PCR.

BACKGROUND: Francisella tularensis is a fastidious, Gram-negative coccobacillus and is the causative agent of tularemia. To assess viability yet overcome lengthy incubation periods, a culture-based PCR method was used to detect early growth of the lowest possible number of F. tularensis cells. This method utilized a previously developed enhanced F. tularensis growth medium and is based on the change in PCR cycle threshold at the start and end of each incubation. RESULTS: To test method robustness, a virulent Type A1 (Schu4) and B (IN99) strain and the avirulent Live Vaccine Strain (LVS) were incubated with inactivated target cells, humic acid, drinking and well water, and test dust at targeted starting concentrations of 1, 10, and 100 CFU mL- 1 (low, mid, and high, respectively). After 48 h, LVS growth was detected at all targeted concentrations in the presence of 106 inactivated LVS cells; while Schu4 and IN99 growth was detected in the presence of 104 Schu4 or IN99 inactivated cells at the mid and high targets. Early detection of F. tularensis growth was strain and concentration dependent in the presence of fast-growing well water and test dust organisms. In contrast, growth was detected at each targeted concentration by 24 h in humic acid and drinking water for all strains. CONCLUSIONS: Results indicated that the culture-based PCR assay is quick, sensitive, and specific while still utilizing growth as a measure of pathogen viability. This method can circumvent lengthy incubations required for Francisella identification, especially when swift answers are needed during epidemiological investigations, remediation efforts, and decontamination verification.

[A severely ill 33-year-old woman with hepatic abscesses]. / Schweres Krankheitsgefühl und Leberabszesse bei einer 33­jährigen Patientin.

A 33-year-old woman in a seriously ill state presented with hepatic abscesses. The proof of epitheloid-like reactions by biopsy and further serological analysis led to the final diagnosis of tularemia, which represents a rare disease in Germany. Thereafter targeted antibiotic therapy was successfully initiated. The contribution of simultaneously diagnosed celiac disease to the unusual manifestation of tularemia in the liver, remains uncertain.

Phylogenetic Analysis of Francisella tularensis Group A.II Isolates from 5 Patients with Tularemia, Arizona, USA, 2015-2017.

We examined 5 tularemia cases in Arizona, USA, during 2015-2017. All were caused by Francisella tularensis group A.II. Genetically similar isolates were found across large spatial and temporal distances, suggesting that group A.II strains are dispersed across long distances by wind and exhibit low replication rates in the environment.

Multiplex Detection of Three Select Agents Directly from Blood by Use of the GeneXpert System.

Francisella tularensis, Bacillus anthracis, and Yersinia pestis are tier 1 select agents with the potential to rapidly cause severe disease. Rapid detection of these bacteria from patient samples at the point of care could contribute to improved clinical outcomes in the event of a bioterrorism attack. A multiplex nested PCR assay for detection of F. tularensis, B. anthracis, and Y. pestis directly from patient blood samples was developed using the GeneXpert system. The multiplex GeneXpert cartridge-based assay includes all necessary sample processing and amplification reagents. Blood samples spiked with different numbers of CFU were used to measure the analytical limit of detection (LOD) and dynamic range. Sensitivity was determined by testing spiked blood samples and negative-control blood in a blind manner. Specificity was determined by testing against nontarget pathogens and blood samples from clinical patients. The assay LOD was 8.5 CFU/ml for F. tularensis, 10 CFU/ml for B. anthracis, and 4.5 CFU/ml for Y. pestis The sensitivity was 100% at the LOD for all three select agent bacteria in spiked patient blood samples. The assay specificity was 100% when it was tested against both nontarget pathogens and clinical patient blood samples. The total assay time was approximately 100 min. This automated assay, which is suitable for use at the point of care, identifies three select agents directly in blood without the need for enrichment with a high sensitivity within 100 min. This assay may enable rapid detection and treatment of patients infected with the target organisms in the event of a bioterrorism attack.

Epidemiological survey of tularemia in Ilam Province, west of Iran.

BACKGROUND: Francisella tularensis is the causative agent of tularemia in humans and a large number of animal species. Considering recent evidence of the circulation of this bacterium in different parts of Iran, especially in the western provinces, the aim of current study was to determine the tularemia seroprevalence in the human population living in Ilam Province. METHODS: In 2015, 360 serum samples were collected from five groups of people: ranchers (n = 112), farmers (n = 79), butchers and slaughterhouse workers (n = 61), Nature Conservation Officers (n = 34), and referents of medical diagnostic laboratories (n = 74). These samples were tested for the presence of anti- F. tularensis IgG antibodies using the ELISA method. RESULTS: According to the ELISA manufacturer cutoffs, we found that 10 (2.78%) and 9 (2.5%) sera, respectively, were positive or borderline for F. tularensis IgG antibodies. The highest tularemia seroprevalence was observed among farmers (7.59%). CONCLUSIONS: Our results strongly support the circulation of tularemia in Ilam Province. Because no human tularemia case has been reported so far in this province, we recommend specific education programs to increase knowledge of local health care professionals about this important zoonotic disease.

Francisella tularensis in Swedish predators and scavengers.

Tularaemia is a zoonotic disease, in Europe caused by Francisella tularensis subsp. holarctica. Many lagomorphs and a variety of small rodents are wildlife species prone to develop clinical disease, while predators and scavengers are relatively resistant and may serve as sentinels. Blood samples from 656 Swedish wild predators and scavengers were serologically investigated using slide agglutination and microagglutination. In the slide agglutination test, 34 seropositive animals were detected, and they were found among all species investigated: brown bear (Ursus arctos), Eurasian lynx (Lynx lynx), raccoon dog (Nyctereutes procyonoides), red fox (Vulpes vulpes), wild boar (Sus scrofa), wolf (Canis lupus) and wolverine (Gulo gulo). Due to haemolysis the microagglutination test was more difficult to read at low titres, and only 12 animals were classified as seropositive. F. tularensis subsp. holarctica was detected by a polymerase chain reaction in lymphatic tissues of the head in one brown bear, one red fox and one wolf. The significance of this finding regarding possible latency of infection is not clear. In conclusion, the results of this study indicate that all predator and scavenger species included in this study may serve as sentinels for tularaemia in Sweden. Their role as reservoirs is unclear.

Severe infections due to Francisella tularensis ssp. holarctica in solid organ transplant recipient: report of two cases and review of literature.

BACKGROUND: Tularemia is a rare zoonotic infection caused by bacterium Francisella tularensis. It has been well described in immunocompetent patients but poorly described in immunocompromised patients notably in solid organ transplant recipients. CASE PRESENTATIONS: We report here two cases of tularemia in solid organ transplant recipients including first case after heart transplant. We also carried out an exhaustive review of literature describing characteristics of this infection in solid organ transplant recipients.

Large outbreak of tularaemia, central Sweden, July to September 2019.

On 31 of July 2019, the Public Health Agency of Sweden was alerted about an increasing number of tularaemia cases in Gävleborg, a county in central Sweden. The number of cases increased thereafter peaking at about 150 reports of illnesses every week. As at 6 October, a total of 979 cases (734 laboratory-confirmed) have been reported, mainly from counties in central Sweden. The outbreak is now considered over (as at 14 October).

Molecular identification of the source of an uncommon tularaemia outbreak, Germany, autumn 2016.

BackgroundIn 2016, an uncommon outbreak of oropharyngeal tularaemia involving six human cases occurred in Germany, caused by drinking contaminated fresh must after a grape harvest.AimWe describe the details of laboratory investigations leading to identification of the outbreak strain, its characterisation by next generation sequencing (NGS) and the finding of the possible source of contamination.MethodsWe incubated wine samples in different media and on agar plates. NGS was performed on DNA isolated from young wine, sweet reserve and an outbreak case's lymph node. A draft genome of the outbreak strain was generated. Vertebrate-specific PCRs using primers targeting the mitochondrial cytochrome b gene and product analyses by blast search were used to identify the putative source of must contamination.ResultsNo bacterial isolate could be obtained. Analysis of the draft genome sequence obtained from the sweet reserve attributed this sequence to Francisella tularensis subsp. holarctica, belonging to the B.12/B.34 phylogenetic clade (erythromycin-resistant biovar II). In addition, the DNA sequence obtained from the case's isolate supported our hypothesis that infection was caused by drinking contaminated must. The vertebrate-specific cytochrome b sequence derived from the young wine and the sweet reserve could be assigned to Apodemus sylvaticus (wood mouse), suggesting that a wood mouse infected with F. tularensis may have contaminated the must.ConclusionThe discovered source of infection and the transmission scenario of F. tularensis in this outbreak have not been observed previously and suggest the need for additional hygienic precautionary measures when processing and consuming freshly pressed must.