Clinical characteristics in a sentinel case as well as in a cluster of tularemia patients associated with grape harvest

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.

Tularemia treatment: experimental and clinical data

Tularemia is a zoonosis caused by the Gram negative, facultative intracellular bacterium Francisella tularensis. This disease has multiple clinical presentations according to the route of infection, the virulence of the infecting bacterial strain, and the underlying medical condition of infected persons. Systemic infections (e.g., pneumonic and typhoidal form) and complications are rare but may be life threatening. Most people suffer from local infection (e.g., skin ulcer, conjunctivitis, or pharyngitis) with regional lymphadenopathy, which evolve to suppuration in about 30% of patients and a chronic course of infection. Current treatment recommendations have been established to manage acute infections in the context of a biological threat and do not consider the great variability of clinical situations. This review summarizes literature data on antibiotic efficacy against F. tularensis in vitro, in animal models, and in humans. Empirical treatment with beta-lactams, most macrolides, or anti-tuberculosis agents is usually ineffective. The aminoglycosides gentamicin and streptomycin remain the gold standard for severe infections, and the fluoroquinolones and doxycycline for infections of mild severity, although current data indicate the former are usually more effective. However, the antibiotic treatments reported in the literature are highly variable in their composition and duration depending on the clinical manifestations, the age and health status of the patient, the presence of complications, and the evolution of the disease. Many patients received several antibiotics in combination or successively. Whatever the antibiotic treatment administered, variable but high rates of treatment failures and relapses are still observed, especially in patients treated more then 2-3 weeks after disease onset. In these patients, surgical treatment is often necessary for cure, including drainage or removal of suppurative lymph nodes or other infectious foci. It is currently difficult to establish therapeutic recommendations, particularly due to lack of comparative randomized studies. However, we have attempted to summarize current knowledge through proposals for improving tularemia treatment which will have to be discussed by a group of experts. A major factor in improving the prognosis of patients with tularemia is the early administration of appropriate treatment, which requires better medical knowledge and diagnostic strategy of this disease.

Ulceroglandular form of tularemia after squirrel bite: a case report

Background

The diagnosis of tularemia is not often considered in Germany as the disease is still rare in this country. Nonetheless, Francisella tularensis, the causative agent of tularemia, can infect numerous animal species and should, therefore, not be neglected as a dangerous pathogen. Tularemia can lead to massively swollen lymph nodes and might even be fatal without antibiotic treatment. To our knowledge, the case described here is the first report of the disease caused by a squirrel bite in Germany.

Case presentation

A 59-year-old German woman with a past medical history of hypothyroidism and cutaneous lupus erythematosus presented at the emergency room at St. Katharinen Hospital with ongoing symptoms and a swollen right elbow persisting despite antibiotic therapy with cefuroxime for 7 days after she had been bitten (right hand) by a wild squirrel (Eurasian red squirrel). After another 7 days of therapy with piperacillin/tazobactam, laboratory analysis using real-time polymerase chain reaction (PCR) confirmed the suspected diagnosis of tularemia on day 14. After starting the recommended antibiotic treatment with ciprofloxacin, the patient recovered rapidly.

Conclusion

This is the first report of a case of tularemia caused by a squirrel bite in Germany. A naturally infected squirrel has recently been reported in Switzerland for the first time. The number of human cases of tularemia has been increasing over the last years and, therefore, tularemia should be taken into consideration as a diagnosis, especially in a patient bitten by an animal who also presents with headache, increasing pain, lymphadenitis, and fever, as well as impaired wound healing. The pathogen can easily be identified by a specific real-time PCR assay of wound swabs and/or by antibody detection, for example by enzyme-linked immunosorbent assay (ELISA), if the incident dates back longer than 2 weeks.

PEDIATRIC TULAREMIA– A CASE SERIES FROM A SINGLE CENTER IN SWITZERLAND

Background

The incidence of tularemia has recently increased throughout Europe. Pediatric tularemia typically presents with ulceroglandular or glandular disease and requires antimicrobial therapy not used in the empirical management of childhood acute lymphadenitis. We describe the clinical presentation and course in a case series comprising 20 patients.

Methods

This is a retrospective analysis of a single-center case series of microbiologically confirmed tularemia in patients <16 years of age diagnosed between 2010 and 2021.

Results

Nineteen patients (95%) presented with ulceroglandular (n = 14) or glandular disease (n = 5), respectively. A characteristic entry site lesion (eschar) was present in 14 (74%). Fever was present at illness onset in 15 patients (75%) and disappeared in all patients before targeted therapy was initiated. The diagnosis was confirmed by serology in 18 patients (90%). While immunochromatography was positive as early as on day 7, a microagglutination test titer 1:≥160 was found no earlier than on day 13. Sixteen patients (80%) were initially treated with an antimicrobial agent ineffective against F. tularensis. The median delay (range) from illness onset to initiation of targeted therapy was 12 (6–40) days. Surgical incision and drainage were ultimately performed in 12 patients (60%).

Conclusions

Pediatric tularemia in Switzerland usually presents with early, self-limiting fever and a characteristic entry site lesion with regional lymphadenopathy draining the scalp or legs. Particularly in association with a tick exposure history, this presentation may allow early first-line therapy with an agent specifically targeting F. tularensis, potentially obviating the need for surgical therapy.

Dangerous Pathogens as a Potential Problem for Public Health

Pathogens are various organisms, such as viruses, bacteria, fungi, and protozoa, which can cause severe illnesses to their hosts. Throughout history, pathogens have accompanied human populations and caused various epidemics. One of the most significant outbreaks was the Black Death, which occurred in the 14th century and caused the death of one-third of Europe's population. Pathogens have also been studied for their use as biological warfare agents by the former Soviet Union, Japan, and the USA. Among bacteria and viruses, there are high priority agents that have a significant impact on public health. Bacillus anthracis, Francisella tularensis, Yersinia pestis, Variola virus, Filoviruses (Ebola, Marburg), Arenoviruses (Lassa), and influenza viruses are included in this group of agents. Outbreaks and infections caused by them might result in social disruption and panic, which is why special operations are needed for public health preparedness. Antibiotic-resistant bacteria that significantly impede treatment and recovery of patients are also valid threats. Furthermore, recent events related to the massive spread of Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are an example of how virus-induced diseases cannot be ignored. The impact of outbreaks, such as SARS-CoV-2, have had far-reaching consequences beyond public health. The economic losses due to lockdowns are difficult to estimate, but it would take years to restore countries to pre-outbreak status. For countries affected by the 2019 coronavirus disease (COVID-19), their health systems have been overwhelmed, resulting in an increase in the mortality rate caused by diseases or injuries. Furthermore, outbreaks, such as SARS-CoV-2, will induce serious, wide-ranging (and possibly long-lasting) psychological problems among, not only health workers, but ordinary citizens (this is due to isolation, quarantine, etc.). The aim of this paper is to present the most dangerous pathogens, as well as general characterizations, mechanisms of action, and treatments.

Outbreak of Tularemia in a Group of Hunters in Germany in 2018-Kinetics of Antibody and Cytokine Responses

In November 2018, an outbreak of tularemia occurred among hare hunters in Bavaria, Germany. At least one infected hare was confirmed as the source of infection. A number of hunting dogs showed elevated antibody titers to Francisella tularensis, but the absence of titer increases in subsequent samples did not point to acute infections in dogs. Altogether, 12 persons associated with this hare hunt could be diagnosed with acute tularemia by detection of specific antibodies. In nine patients, the antibody and cytokine responses could be monitored over time. Eight out of these nine patients had developed detectable antibodies three weeks after exposure; in one individual the antibody response was delayed. All patients showed an increase in various cytokines and chemokines with a peak for most mediators in the first week after exposure. Cytokine levels showed individual variations, with high and low responders. The kinetics of seroconversion has implications on serological diagnoses of tularemia.

Francisella tularensis Subspecies holarctica and Tularemia in Germany

Tularemia is a zoonotic disease caused by Francisella tularensis a small, pleomorphic, facultative intracellular bacterium. In Europe, infections in animals and humans are caused mainly by Francisella tularensis subspecies holarctica. Humans can be exposed to the pathogen directly and indirectly through contact with sick animals, carcasses, mosquitoes and ticks, environmental sources such as contaminated water or soil, and food. So far, F. tularensis subsp. holarctica is the only Francisella species known to cause tularemia in Germany. On the basis of surveillance data, outbreak investigations, and literature, we review herein the epidemiological situation-noteworthy clinical cases next to genetic diversity of F. tularensis subsp. holarctica strains isolated from patients. In the last 15 years, the yearly number of notified cases of tularemia has increased steadily in Germany, suggesting that the disease is re-emerging. By sequencing F. tularensis subsp. holarctica genomes, knowledge has been added to recent findings, completing the picture of genotypic diversity and geographical segregation of Francisella clades in Germany. Here, we also shortly summarize the current knowledge about a new Francisella species (Francisella sp. strain W12-1067) that has been recently identified in Germany. This species is the second Francisella species discovered in Germany.