Typhoidal tularemia is a severe systemic form of tularemia caused by Francisella tularensis, characterized by high fever, constitutional symptoms, and absence of localizing signs (no skin ulcers, no regional lymphadenopathy). It carries the highest fatality rate among tularemia forms — up to 60% if untreated — and is a CDC Category A bioterrorism agent. [1-3]
1. History
- Exposure history is critical: tick bites, deer fly bites, handling rabbits/rodents (skinning, dressing), mowing/landscaping (aerosolized organisms), contaminated water ingestion, laboratory exposure [4-5]
- Incubation period: 3–5 days (range 1–14 days) [2][4]
- Abrupt onset of high fever (38–40°C), chills, rigors, severe headache, myalgia (often prominent low back pain), malaise, anorexia [3]
- Prominent GI symptoms: nausea, vomiting, diarrhea, abdominal pain — may dominate the presentation [3][6]
- Dry or slightly productive cough, substernal tightness may occur even without frank pneumonia [3]
- Progressive weakness, sweats, weight loss if untreated [3]
- Ask about occupational exposures (foresters, farmers, hunters, veterinarians, lab workers) and geographic endemicity (south-central US states: Arkansas, Missouri, Oklahoma, Kansas) [4-5]
- Key negative: absence of skin ulcer or palpable lymphadenopathy distinguishes typhoidal from ulceroglandular forms [2-3]
2. Alarm Features
- Sepsis/septic shock: hypotension, tachycardia, altered mental status
- Neurological symptoms: confusion, stupor, behavioral changes — suggest severe systemic disease [2]
- Respiratory distress: secondary pleuropneumonia from hematogenous spread can develop in any form [3]
- Pulse-temperature dissociation (relative bradycardia) — noted in up to 42% of patients [3]
- Hemoptysis, pleuritic pain, or rapidly progressive dyspnea
- Immunocompromised patients (anti-TNF therapy, transplant recipients) are at particular risk for severe/atypical presentations [2][7]
- Delayed treatment (>2–3 weeks from onset) is associated with significantly worse outcomes and higher treatment failure rates [8]
3. Medications
- Severe/typhoidal tularemia — first-line: parenteral aminoglycosides [9]
- Gentamicin 5 mg/kg/day IV divided q8h (or once daily dosing per institutional protocol); adjust for renal function
- Streptomycin 15 mg/kg IM q12h (max 2 g/day) — historically drug of choice but limited availability
- Duration: 10–14 days [3][10]
- Alternatives for mild-moderate disease or step-down:
- Ciprofloxacin 400 mg IV q12h → 750 mg PO BID (10–14 days) [9][11]
- Levofloxacin 500–750 mg IV/PO daily
- Doxycycline 100 mg IV/PO BID (minimum 14 days to reduce relapse) [3][9]
- 2025 CDC guidelines now designate fluoroquinolones and doxycycline as first-line for outbreaks of any size, with aminoglycosides as alternatives for severe disease [11]
- Contraindicated/ineffective: beta-lactams, most macrolides, anti-TB agents — F. tularensis is intrinsically resistant [8-9]
- Bacteriostatic agents (tetracyclines, chloramphenicol) carry higher relapse rates (~10–15%) than fluoroquinolones (~5–10%) [2]
- Pregnancy: gentamicin for severe disease; azithromycin may be considered for mild type B infections in western Europe [2]
4. Diet
- No specific dietary triggers or restrictions
- Aggressive IV fluid resuscitation in septic/dehydrated patients
- Avoid consumption of undercooked wild game (rabbit, squirrel) and untreated surface water — these are transmission routes [1][5]
- Long-term: standard nutrition to support recovery from prolonged debilitating illness
5. Review of Systems
- Constitutional: fever pattern (sustained high), night sweats, weight loss, profound fatigue
- GI: diarrhea, abdominal pain, nausea/vomiting (may mimic enteric fever) [3][6]
- Respiratory: cough (dry or productive), dyspnea, pleuritic chest pain, hemoptysis — screen for secondary pneumonia [3]
- Neurological: confusion, headache, behavioral changes, meningismus [2]
- MSK: diffuse myalgias, arthralgias, prominent low back pain [3]
- Dermatologic: erythema nodosum, rash (uncommon in typhoidal form but possible) [2]
6. Collateral History and Family History
- Collateral: household members with similar symptoms (shared exposure, not person-to-person); recent outdoor activities, hunting, tick exposure in endemic areas
- Occupational history: farming, forestry, landscaping, veterinary work, laboratory work [4][6]
- Travel to endemic regions (south-central US, Scandinavia, Turkey, central Europe)
- Family history is generally not relevant (non-hereditary), but household clustering from shared environmental exposure should raise suspicion
- In a bioterrorism context, clustering of febrile illness without localizing signs in a non-endemic area is a critical epidemiologic clue [3]
7. Risk Factors
- Tick/arthropod exposure (most common US vector: Dermacentor variabilis, Amblyomma americanum) [4-5]
- Handling infected animals (rabbits, hares, rodents, cats) [5][9]
- Occupational: hunters, trappers, farmers, landscapers, veterinarians, laboratory workers [4][12]
- Ingestion of contaminated water or undercooked game [1]
- Inhalation of aerosolized bacteria (mowing over animal carcasses, laboratory accidents) [12]
- Immunosuppression (anti-TNF agents, transplant, HIV) — increased risk of severe/disseminated disease [2][7]
- Older age — systemic disease occurs more commonly in older patients [4]
- Male sex (65% of US cases) [4]
- Geographic: south-central US states; Scandinavia and Turkey in Europe [1][4]
8. Differential Diagnosis
The typhoidal form is a great mimicker due to its nonspecific presentation:
- Typhoid/enteric fever (Salmonella typhi) — similar fever pattern, GI symptoms, relative bradycardia; distinguished by travel history, blood cultures
- Brucellosis — undulant fever, sweats, hepatosplenomegaly; animal/dairy exposure; serologic cross-reactivity with tularemia [2]
- Q fever (Coxiella burnetii) — fever, headache, pneumonia; livestock exposure
- Bacterial sepsis (other gram-negative organisms) — blood cultures typically positive
- Lymphoma/hematologic malignancy — prolonged fever, weight loss; imaging may mimic tularemia (hypermetabolic mediastinal nodes on PET/CT) [13]
- Tuberculosis — chronic fever, weight loss, granulomatous inflammation on biopsy; tularemia can produce caseating granulomas mimicking TB [14]
- Endocarditis — prolonged fever, culture-negative endocarditis is a consideration
- Rickettsial diseases (RMSF, ehrlichiosis) — tick-borne, fever, but typically with rash or cytopenias
- Pneumonic plague (Yersinia pestis) — in bioterrorism context; more fulminant course
- Infectious mononucleosis/EBV — in younger patients with fever and lymphadenopathy
9. Past Medical History
- Prior tularemia episodes (immunity is only partial; reinfection can occur) [15]
- Immunocompromising conditions: HIV, organ transplant, biologics (especially anti-TNF agents) [2][7]
- Chronic lung disease (increases risk of pneumonic complications)
- Renal impairment (affects aminoglycoside dosing)
- Prior beta-lactam treatment failure for a febrile illness — should raise suspicion for tularemia [16]
10. Physical Exam
- Vital signs: High fever (38–40°C), pulse-temperature dissociation (relative bradycardia) in up to 42%; tachypnea if pneumonic component; hypotension in sepsis [3]
- General: toxic-appearing, diaphoretic, cachectic if prolonged illness
- HEENT: pharyngeal erythema (if oropharyngeal component); no localizing findings in pure typhoidal form
- Lymph nodes: absence of regional lymphadenopathy is a defining feature of typhoidal tularemia [2-3]
- Skin: no inoculation ulcer — absence of skin findings distinguishes from ulceroglandular form; look for erythema nodosum [2]
- Lungs: may be clear or have crackles/decreased breath sounds if secondary pneumonia develops [3]
- Abdomen: hepatosplenomegaly possible; diffuse tenderness (may mimic acute abdomen) [6]
- Neuro: assess for confusion, stupor, meningismus [2]
11. Lab Studies
- CBC: leukocytosis or normal WBC; thrombocytopenia possible in severe disease
- CMP: elevated transaminases, elevated LDH, hyponatremia
- Inflammatory markers: elevated CRP, ESR, procalcitonin
- Blood cultures: often negative (positive in ~50% of severe cases when using enriched media); must alert the lab — F. tularensis is a BSL-3 organism and poses a serious laboratory hazard [5][9-10][17]
- Serology (gold standard for diagnosis): [2][5]
- Microagglutination test (MAT) or indirect immunofluorescence assay (IFA)
- Seroconversion or 4-fold rise in paired sera (acute + convalescent at 2–3 weeks)
- Single titer ≥1:128 is presumptive
- Antibodies often negative in first 7–10 days — do not rely on a single early negative [5]
- PCR: highly sensitive and specific from clinical specimens; most useful in first week of illness [2][5]
- Lactate, coagulation studies if sepsis suspected
12. Imaging
- Chest X-ray: may be normal or show nonspecific infiltrates, hilar/mediastinal lymphadenopathy, pleural effusion [10][12]
- Chest CT (if respiratory symptoms or concern for pneumonic component):
- Subpleural round consolidations, mediastinal lymphadenopathy, pulmonary nodules, pleural effusion [13][18]
- Can mimic lung cancer or lymphoma — PET/CT may show intensely hypermetabolic lesions [13]
- Abdominal imaging: hepatosplenomegaly; splenic/hepatic abscesses in disseminated disease
- Imaging is nonspecific and should not delay empiric treatment when clinical suspicion is high [10]
13. Special Tests
- Tularemia serology (MAT, IFA, ELISA) — primary diagnostic modality [2][19]
- PCR from blood, wound swabs, lymph node aspirates, respiratory specimens — rapid confirmation [2][5]
- Direct immunofluorescence assay (DFA) on tissue specimens [5]
- Immunohistochemical (IHC) staining of biopsy specimens [5]
- Culture on cysteine-enriched media (chocolate agar, cysteine heart agar) — requires BSL-3 precautions [2]
- MALDI-TOF mass spectrometry can identify F. tularensis from culture isolates [2]
- No validated clinical scoring system exists for tularemia; diagnosis relies on clinical suspicion + exposure history + serologic/molecular confirmation
14. ECG
- No pathognomonic ECG findings for tularemia
- ECG indicated if:
- Sepsis with hemodynamic instability
- Pulse-temperature dissociation (rule out conduction abnormalities)
- Myocarditis (rare complication) — look for diffuse ST changes, low voltage, new arrhythmias
- Baseline before aminoglycoside therapy
15. Assessment
- Typhoidal tularemia is a severe systemic infection with the highest mortality among tularemia forms [1-2]
- The hallmark is fever of unknown origin with no localizing signs in a patient with relevant exposure history
- Frequently misdiagnosed initially — median time to diagnosis can exceed 3 weeks [4][6][16]
- Complications include secondary pneumonia, sepsis, meningitis, brain abscess, hepatosplenic abscesses, and erythema nodosum [2-3]
- Prognosis is strongly tied to early appropriate antibiotic therapy — treatment initiated >2–3 weeks after onset has significantly higher failure and relapse rates [8]
- Overall US case fatality rate with treatment: ~2.3%; without treatment for typhoidal/pneumonic forms: up to 30–60% [1][17][20]
16. Treatment Plan
Initial stabilization:
- IV fluid resuscitation, hemodynamic support if septic
- Notify the microbiology laboratory immediately if tularemia is suspected [9-10]
- Respiratory isolation is not required (no person-to-person transmission); standard precautions are adequate [10]
Antibiotic therapy for typhoidal (severe) tularemia:
- Considerable clinical improvement is generally noted within 48 hours of appropriate therapy [15]
- Step-down from IV to PO when clinically stable
- Avoid beta-lactams — intrinsically resistant [8-9]
17. Disposition
- Admit all patients with typhoidal tularemia — this is by definition severe systemic disease [1-2]
- ICU admission if septic shock, respiratory failure, or neurological compromise
- Hospitalization for IV aminoglycoside therapy and monitoring
- Discharge criteria: afebrile ≥24–48 hours, hemodynamically stable, tolerating PO antibiotics, improving clinically
- Step-down to oral fluoroquinolone or doxycycline to complete course as outpatient
- Mandatory reporting: tularemia is a nationally notifiable disease — report to local/state health department [5][11]
- Infectious disease consultation recommended for all cases
- Bioterrorism consideration: if no natural exposure identified and clustering of cases, notify public health authorities immediately [3][11]
18. Follow Up / Return Precautions
- Follow-up within 1 week of discharge to assess clinical response and repeat labs
- Convalescent serology at 2–3 weeks after acute specimen to confirm seroconversion [2][5]
- Monitor for relapse — occurs in 5–15% of cases depending on antibiotic used; higher with doxycycline and shorter courses [2][8]
- Return precautions — seek immediate care for:
- Recurrence of fever after initial improvement
- New or worsening respiratory symptoms (cough, dyspnea, pleuritic pain)
- Confusion, altered mental status
- Persistent GI symptoms (vomiting, diarrhea, abdominal pain)
- New lymphadenopathy or skin lesions
- Expected recovery: significant improvement within 48 hours of appropriate antibiotics; full recovery may take weeks to months in severe cases, with prolonged fatigue and debility [3][15]
- Counsel that immunity is only partial — reinfection is possible with future exposures [15]
References
1. Tularemia for Clinicians: An Up-to-Date Review on Epidemiology, Diagnosis, Prevention and Treatment. — Antonello RM, Giacomelli A, Riccardi N. European Journal of Internal Medicine. 2025.
2. Tularemia for Clinicians: An Up-to-Date Review on Epidemiology, Diagnosis, Prevention and Treatment. — Antonello RM, Giacomelli A, Riccardi N. European Journal of Internal Medicine. 2025.
3. Tularemia for Clinicians: An Up-to-Date Review on Epidemiology, Diagnosis, Prevention and Treatment. — Antonello RM, Giacomelli A, Riccardi N. European Journal of Internal Medicine. 2025.
4. Tularaemia: Clinical Aspects in Europe. — Maurin M, Gyuranecz M. The Lancet. Infectious Diseases. 2016.
5. Tularaemia: Clinical Aspects in Europe. — Maurin M, Gyuranecz M. The Lancet. Infectious Diseases. 2016.
6. Tularemia as a Biological Weapon: Medical and Public Health Management. — Dennis DT, Inglesby TV, Henderson DA, et al. The Journal of the American Medical Association. 2001.
7. Tularemia as a Biological Weapon: Medical and Public Health Management. — Dennis DT, Inglesby TV, Henderson DA, et al. The Journal of the American Medical Association. 2001.
8. Clinical Recognition and Management of Tularemia in Missouri: A Retrospective Records Review of 121 Cases. — Weber IB, Turabelidze G, Patrick S, et al. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2012.
9. Clinical Recognition and Management of Tularemia in Missouri: A Retrospective Records Review of 121 Cases. — Weber IB, Turabelidze G, Patrick S, et al. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2012.
10. Tickborne Diseases of the United States: A Reference Manual for Healthcare Providers Sixth Edition. — Nancy Shadick MD MPH, Nancy Maher MPH, Dennis Hoak MD United States Centers for Disease Control and Prevention (2022). 2022.
11. Tickborne Diseases of the United States: A Reference Manual for Healthcare Providers Sixth Edition. — Nancy Shadick MD MPH, Nancy Maher MPH, Dennis Hoak MD United States Centers for Disease Control and Prevention (2022). 2022.
12. Francisella Tularensis as the Cause of Protracted Fever. — Antonitsch L, Weidinger G, Stanek G, Markowicz M. BMC Infectious Diseases. 2020.
13. Francisella Tularensis as the Cause of Protracted Fever. — Antonitsch L, Weidinger G, Stanek G, Markowicz M. BMC Infectious Diseases. 2020.
14. Pulmonary tularaemia in a female adolescent with inflammatory bowel disease receiving infliximab: Do not miss the diagnosis. — Schwarzová V, Schwarz J, Mitrová K, et al. Pediatric Pulmonology. 2023.
15. Pulmonary tularaemia in a female adolescent with inflammatory bowel disease receiving infliximab: Do not miss the diagnosis. — Schwarzová V, Schwarz J, Mitrová K, et al. Pediatric Pulmonology. 2023.
16. Tularemia Treatment: Experimental and Clinical Data. — Maurin M, Pondérand L, Hennebique A, et al. Frontiers in Microbiology. 2023.
17. Tularemia Treatment: Experimental and Clinical Data. — Maurin M, Pondérand L, Hennebique A, et al. Frontiers in Microbiology. 2023.
18. Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the Infectious Diseases Society of America. — Stevens DL, Bisno AL, Chambers HF, et al. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2014.
19. Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the Infectious Diseases Society of America. — Stevens DL, Bisno AL, Chambers HF, et al. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2014.
20. Clinical Management of Potential Bioterrorism-Related Conditions. — Adalja AA, Toner E, Inglesby TV. The New England Journal of Medicine. 2015.
21. Clinical Management of Potential Bioterrorism-Related Conditions. — Adalja AA, Toner E, Inglesby TV. The New England Journal of Medicine. 2015.
22. Tularemia Antimicrobial Treatment and Prophylaxis: CDC Recommendations for Naturally Acquired Infections and Bioterrorism Response - United States, 2025. — Nelson CA, Meaney-Delman D, Fleck-Derderian S, Winberg J, Mead PS. MMWR. Recommendations and Reports : Morbidity and Mortality Weekly Report. Recommendations and Reports. 2025.
23. Tularemia Antimicrobial Treatment and Prophylaxis: CDC Recommendations for Naturally Acquired Infections and Bioterrorism Response - United States, 2025. — Nelson CA, Meaney-Delman D, Fleck-Derderian S, Winberg J, Mead PS. MMWR. Recommendations and Reports : Morbidity and Mortality Weekly Report. Recommendations and Reports. 2025.
24. Tularaemia. — Tärnvik A, Berglund L. The European Respiratory Journal. 2003.
25. Tularaemia. — Tärnvik A, Berglund L. The European Respiratory Journal. 2003.
26. Pulmonary Tularemia: A Diagnosis Not to Overlook. — Zaghdoudi A, Robin F, Moulinie J, et al. International Journal of Infectious Diseases : IJID : Official Publication of the International Society for Infectious Diseases. 2026.
27. Pulmonary Tularemia: A Diagnosis Not to Overlook. — Zaghdoudi A, Robin F, Moulinie J, et al. International Journal of Infectious Diseases : IJID : Official Publication of the International Society for Infectious Diseases. 2026.
28. A Clinical Pitfall in Caseating Necrotizing Granulomatous Lymphadenitis: Tularemia. — Özan Köse S, Erdem H, Köse ÖC, Yılmaz Ertürk F. Diagnostic Microbiology and Infectious Disease. 2025.
29. A Clinical Pitfall in Caseating Necrotizing Granulomatous Lymphadenitis: Tularemia. — Özan Köse S, Erdem H, Köse ÖC, Yılmaz Ertürk F. Diagnostic Microbiology and Infectious Disease. 2025.
30. Tick-Borne Diseases in the United States. — Spach DH, Liles WC, Campbell GL, et al. The New England Journal of Medicine. 1993.
31. Tick-Borne Diseases in the United States. — Spach DH, Liles WC, Campbell GL, et al. The New England Journal of Medicine. 1993.
32. Tularemia in Pediatric Patients: A Case Series and Review of the Literature. — Kossadoum RF, Baron A, Parizot M, et al. The Pediatric Infectious Disease Journal. 2025.
33. Tularemia in Pediatric Patients: A Case Series and Review of the Literature. — Kossadoum RF, Baron A, Parizot M, et al. The Pediatric Infectious Disease Journal. 2025.
34. Tularemia Clinical Manifestations, Antimicrobial Treatment, and Outcomes: An Analysis of US Surveillance Data, 2006-2021. — Wu HJ, Bostic TD, Horiuchi K, et al. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2024.
35. Tularemia Clinical Manifestations, Antimicrobial Treatment, and Outcomes: An Analysis of US Surveillance Data, 2006-2021. — Wu HJ, Bostic TD, Horiuchi K, et al. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2024.
36. Treatment Outcome of Severe Respiratory Type B Tularemia Using Fluoroquinolones. — Widerström M, Mörtberg S, Magnusson M, Fjällström P, Johansson AF. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2024.
37. Treatment Outcome of Severe Respiratory Type B Tularemia Using Fluoroquinolones. — Widerström M, Mörtberg S, Magnusson M, Fjällström P, Johansson AF. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2024.
38. Evaluation of in-House and Commercial Serological Tests for Diagnosis of Human Tularemia. — Yanes H, Hennebique A, Pelloux I, et al. Journal of Clinical Microbiology. 2018.
39. Evaluation of in-House and Commercial Serological Tests for Diagnosis of Human Tularemia. — Yanes H, Hennebique A, Pelloux I, et al. Journal of Clinical Microbiology. 2018.
40. Multifaceted effects of F rancisella tularensis on human neutrophil function and lifespan. — Kinkead LC, Allen LA. Immunological Reviews. 2016.
41. Multifaceted effects of F rancisella tularensis on human neutrophil function and lifespan. — Kinkead LC, Allen LA. Immunological Reviews. 2016.