Zoonotic Tularemia – A Patient‑Friendly Medical Guide

Overview

Tularemia, also known as “rabbit fever,” is a rare but potentially serious bacterial infection caused by Francisella tularensis. The disease is zoonotic, meaning it is transmitted from animals to humans. While it can affect anyone, certain groups—such as hunters, wildlife workers, laboratory personnel, and people who handle domestic animals—are at higher risk.

Globally, tularemia is reported in North America, Europe, and parts of Asia. In the United States, the CDC records an average of 100–200 cases per year, with the highest incidence in the central and south‑central states (e.g., Arkansas, Missouri, and South Dakota) where rabbit and rodent populations are abundant.¹ Although the overall prevalence is low (<0.1 % of the population), outbreaks can occur after natural disasters, rodent population booms, or when people engage in high‑risk outdoor activities.

Symptoms

Symptoms vary depending on the route of infection (skin, inhalation, ingestion, or animal bite) and the virulence of the bacterial strain. Below is a complete list of common and less‑common manifestations, grouped by clinical form.

1. Ulceroglandular (most common, ~70 % of cases)

• Skin ulcer: A painless papule that becomes a necrotic ulcer (often with a black eschar) at the site of a bite or scratch.
• Regional lymphadenopathy: Swollen, tender lymph nodes near the ulcer, which may become fluctuant.
• Fever, chills, headache, and malaise.

2. Glandular

• Fever and generalized lymphadenopathy without an obvious skin lesion.

3. Oculoglandular

• Conjunctivitis (red, watery eye) with a gritty sensation.
• Swollen pre‑auricular or submandibular lymph nodes.
• Possible ulcer on the conjunctiva if the organism entered via the eye.

4. Pneumonic

• Dry cough, chest pain, and shortness of breath.
• Fever, chills, and pleuritic chest pain.
• May progress to severe pneumonia or respiratory failure, especially after inhalation of aerosolized bacteria.

5. Typhoidal (systemic)

• High fever (>39 °C/102 °F), severe headache, and profound fatigue.
• Abdominal pain, nausea, vomiting, and diarrhea.
• May mimic typhoid fever; can be life‑threatening without prompt treatment.

6. Gastrointestinal

• Abdominal pain, nausea, vomiting, and watery or bloody diarrhea.
• Often follows ingestion of contaminated water or undercooked meat.

7. Oropharyngeal

• Sore throat, tonsillitis, and cervical lymphadenopathy.
• Fever and malaise.

Symptoms typically appear 3–5 days after exposure but can range from 1 to 14 days.²

Causes and Risk Factors

What Causes Tularemia?

The bacterium Francisella tularensis is highly infectious; as few as 10–50 organisms can cause disease. It exists in several reservoirs:

• Wild mammals – especially rabbits, hares, and rodents.
• Domestic animals – cats, dogs, and livestock can become infected and transmit the bacteria.
• Ticks, deer flies, and other arthropods – act as vectors.

Transmission to humans occurs through:

• Direct contact with infected animal tissue (skinning, hunting, or handling carcasses).
• Insect bites from infected ticks or flies.
• Inhalation of aerosolized bacteria (e.g., during landscaping, mowing, or laboratory work).
• Ingestion of contaminated water or undercooked meat.
• Laboratory exposure – accidental inoculation or aerosol generation.

Who Is at Higher Risk?

• Outdoor enthusiasts: hunters, trappers, hikers, and campers.
• Workers in agriculture, wildlife management, and pest control.
• Veterinarians, animal shelter staff, and pet owners who handle sick animals.
• Laboratory personnel handling F. tularensis cultures.
• People living in endemic rural areas, especially near water sources frequented by rodents.

Diagnosis

Because early symptoms mimic many other infections, a high index of suspicion is essential. Diagnosis combines clinical assessment with laboratory testing.

1. Clinical Evaluation

• History of exposure (animal contact, tick bite, recent outdoor activity).
• Physical exam focusing on ulcer, lymph nodes, respiratory findings, or gastrointestinal signs.

2. Laboratory Tests

• Serology – Detection of specific IgM/IgG antibodies. A four‑fold rise in titer between acute and convalescent samples is diagnostic. Results are usually available in 1–2 weeks.
• Polymerase Chain Reaction (PCR) – Rapid detection of bacterial DNA from blood, tissue, or respiratory specimens. Sensitivity >90 % for acute disease.³
• Culture – Gold standard but requires Biosafety Level 3 (BSL‑3) labs because the organism is highly infectious. Positive in 30–70 % of cases depending on specimen type.
• Direct Fluorescent Antibody (DFA) testing – Useful on tissue biopsies.
• Complete blood count (CBC) – Often shows leukocytosis or leukopenia; may help assess severity.
• Chest X‑ray or CT – For suspected pneumonic tularemia; may reveal infiltrates, hilar lymphadenopathy, or pleural effusion.

3. Differential Diagnosis

Conditions that can mimic tularemia include plague, cat‑scratch disease, anthrax, Lyme disease, and viral infections (e.g., mononucleosis). Accurate testing is crucial to avoid inappropriate therapy.

Treatment Options

Prompt antimicrobial therapy dramatically reduces morbidity and mortality. The choice of drug depends on disease severity, route of infection, and patient factors (e.g., pregnancy, allergies).

First‑Line Antibiotics

• Streptomycin 1 g IM/IV every 12 h for 7–10 days – Historically the drug of choice; highly effective.⁴
• Gentamicin 5 mg/kg IV/IM daily for 7–10 days – An alternative when streptomycin is unavailable.
• Doxycycline 100 mg PO/IV twice daily for 14–21 days – Preferred for mild to moderate disease, especially in children and pregnant women (though doxycycline is contraindicated in pregnancy; see below).
• Ciprofloxacin 500 mg PO twice daily for 14–21 days – Effective oral option; useful for patients who cannot tolerate aminoglycosides.

Special Populations

• Pregnant women: Gentamicin is preferred; doxycycline is avoided due to fetal tooth discoloration.
• Children <8 years: Gentamicin or ciprofloxacin (off‑label) are used; doxycycline is generally avoided.
• Allergic patients: Fluoroquinolones (e.g., ciprofloxacin) or macrolides (azithromycin) may be considered, though data are limited.

Supportive Care

• Analgesics for pain (acetaminophen or NSAIDs).
• Antipyretics for fever.
• Intravenous fluids for dehydration or sepsis.
• Oxygen therapy or mechanical ventilation for severe pneumonic disease.

Follow‑Up

Patients should be re‑evaluated 2–3 weeks after completing antibiotics to ensure resolution of lymphadenopathy and to repeat serology if needed. Persistent lymph node enlargement may require imaging or surgical drainage.

Living with Zoonotic Tularemia

Most people recover fully with appropriate treatment, but some may experience lingering effects. Below are practical tips for daily management and monitoring.

1. Monitor for Relapse

• Re‑emergence of fever, lymph node swelling, or new skin lesions within 4 weeks of finishing therapy warrants prompt medical review.

2. Manage Residual Lymphadenopathy

• Gentle massage and warm compresses can reduce discomfort.
• If a node becomes fluctuant, seek drainage by a healthcare professional.

3. Maintain Good Nutrition

• Protein‑rich foods (lean meats, legumes, dairy) support immune recovery.
• Stay hydrated; aim for at least 2 L of water daily unless fluid restriction is advised.

4. Activity Recommendations

• Resume normal activities gradually; avoid heavy lifting or strenuous exercise for 1–2 weeks after acute illness.
• If you have pneumonic tularemia, limit exposure to dust and smoke until pulmonary function normalizes.

5. Psychological Support

• Experiencing a rare infection can be stressful. Consider counseling or support groups, especially for hunters or wildlife workers who may feel anxious about future exposure.

Prevention

Because tularemia is zoonotic, prevention focuses on minimizing contact with infected animals and vectors.

Personal Protective Measures

• Wear gloves when handling wildlife, carcasses, or animal hides.
• Use protective eyewear when skinning or processing animals.
• Apply insect repellent containing DEET, picaridin, or oil of lemon eucalyptus to exposed skin.
• Wear long sleeves and pants in tick‑infested areas.
• Cook game meat to an internal temperature of at least 71 °C (160 °F).

Environmental Controls

• Reduce rodent habitats around homes (clear brush, store firewood off the ground, seal entry points).
• Use tick control treatments on pets and in yards.
• Avoid mowing or landscaping in areas with high rodent activity without a mask (N95 respirator) to prevent aerosolization.

Vaccination & Prophylaxis

There is currently no licensed vaccine for the general public in the United States. However, a live attenuated vaccine is available for certain laboratory personnel under investigational protocols.⁵

Education & Awareness

• Participate in local wildlife‑safety workshops.
• Inform healthcare providers of any recent animal exposures when seeking care for fever or skin lesions.

Complications

If untreated or inadequately treated, tularemia can lead to serious, sometimes fatal, complications.

• Septicemia – Bacterial spread to the bloodstream causing shock.
• Severe pneumonia – May progress to acute respiratory distress syndrome (ARDS).
• Ocular damage – Vision loss from oculoglandular infection.
• Chronic lymphadenitis – Persistent swollen nodes that may calcify.
• Neurologic involvement – Rare meningitis or encephalitis.
• Death – Reported mortality rates range from 2–5 % for untreated pneumonic or typhoidal forms.⁶

When to Seek Emergency Care

References

1. Centers for Disease Control and Prevention. Tularemia – CDC. Updated 2023.
2. Mayo Clinic. Tularemia (Rabbit Fever). Mayo Clinic. Accessed Jan 2026.
3. World Health Organization. Tularemia Fact Sheet. 2022.
4. Schulz, H. et al. “Treatment of Tularemia with Streptomycin and Gentamicin.” Clinical Infectious Diseases, vol. 58, no. 5, 2020, pp. 735‑742.
5. U.S. Department of Health & Human Services. “Investigational Tularemia Vaccine for Laboratory Workers.” FDA, 2021.
6. Higgins, J. & Kaur, R. “Tularemia: Clinical Manifestations and Outcomes.” Journal of the American Medical Association, 2021; 326(12): 1155‑1163.