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Rabbits Fever (Tularemia) – Comprehensive Medical Guide

Overview

Rabbits fever, more formally known as tularemia, is a rare but potentially serious bacterial infection caused by Francisella tularensis. The organism thrives in wild rodents, rabbits, and other small mammals, and can be transmitted to humans via bites, scratches, inhalation of contaminated dust, or handling infected animal tissue.

Although tularemia can affect anyone, certain groups are more frequently diagnosed:

• People who hunt, trap, or handle wild game (especially rabbits, hares, and rodents).
• Outdoor workers such as landscapers, park rangers, and farmers.
• Veterinarians, laboratory personnel, and researchers who work with the bacterium.
• Individuals living in rural areas of the United States, Scandinavia, and parts of Asia where the disease is endemic.

In the United States, the CDC reports an average of 150–200 confirmed cases per year, a small fraction of the 1.5 million reported cases worldwide each year (WHO).

Symptoms

The clinical picture of tularemia varies with the route of entry. Below is a complete list of possible signs and symptoms, grouped by the most common forms.

Ulceroglandular (most common, ~75% of cases)

• Skin ulcer: A painless papule that becomes a small ulcer (usually 0.5–1 cm) at the site of a bite, scratch, or handling of infected animal tissue.
• Regional lymphadenopathy: Swollen, tender lymph nodes near the ulcer, often enlarging within 3–5 days.
• Fever (38–40 °C / 100–104 °F)
• Chills, sweats
• Headache, malaise, and muscle aches.

Glandular

• Swollen lymph nodes without an evident skin ulcer.
• Fever and systemic symptoms similar to ulceroglandular disease.

Oculoglandular

• Red, painful eye (conjunctivitis) after touching infected material.
• Swollen pre‑auricular or submandibular lymph nodes.
• Blurred vision or photophobia (sensitivity to light).

Oropharyngeal

• Sore throat, ulceration of the tonsils or pharynx.
• Swollen cervical lymph nodes.
• Fever, nausea, and sometimes vomiting.

Pneumonic

• Cough (often dry), chest pain.
• Shortness of breath, rapid breathing.
• Fever, chills, and sometimes hemoptysis (coughing up blood).
• Can develop after inhaling contaminated aerosols or as a complication of untreated ulceroglandular disease.

Typhoidal (systemic)

• High, persistent fever.
• Severe headache, abdominal pain.
• Diarrhea or constipation, sometimes a rash.
• Rapid deterioration if not treated promptly.

Causes and Risk Factors

What Causes Tularemia?

The disease is caused by Francisella tularensis, a gram‑negative, highly infectious bacterium. It survives in water, soil, and animal carcasses. Human infection can occur via:

• Animal bites or scratches – especially from rabbits, hares, squirrels, or groundhogs.
• Direct contact with infected animal tissue or fluids.
• Inhalation of contaminated dust or aerosols (e.g., during lawn mowing, brush clearing, or laboratory work).
• Ingestion of contaminated water or undercooked meat.
• Tick or deer‑fly bites – vectors in many endemic regions.

Who Is at Higher Risk?

• Outdoor enthusiasts and professionals who handle wildlife.
• People who consume untreated water from natural sources.
• Laboratory workers handling F. tularensis cultures (it is a Category A bioterrorism agent).
• Individuals with weakened immune systems (e.g., HIV, transplant recipients, chemotherapy patients).
• Residents of endemic areas during spring–summer when ticks and flies are most active.

Diagnosis

Because the signs of tularemia overlap with many other infections, a high index of suspicion is crucial, especially after a relevant exposure.

Clinical Evaluation

• Detailed history: recent hunting, animal contact, tick bites, or exposure to aerosolized dust.
• Physical examination focusing on ulcer sites, lymph node enlargement, respiratory findings, or eye involvement.

Laboratory Tests

1. Serology – detection of specific antibodies (IgM, IgG). A four‑fold rise in titer between acute and convalescent samples is diagnostic.
2. Culture – growth of F. tularensis from tissue, blood, or fluid. Requires biosafety level 3 (BSL‑3) facilities; not routinely performed in all labs.
3. Polymerase Chain Reaction (PCR) – rapid detection of bacterial DNA from blood, ulcer swabs, or respiratory samples. Increasingly available in reference labs.
4. Complete Blood Count (CBC) – often shows leukocytosis or leukopenia; may help assess severity.
5. Imaging (if pneumonic disease is suspected) – chest X‑ray or CT may reveal infiltrates, nodules, or pleural effusion.

Diagnostic Criteria (CDC)

A confirmed case requires either a positive culture, PCR, or a four‑fold rise in serologic titer. A probable case is based on compatible clinical illness plus a single positive serologic test.

Treatment Options

Early antimicrobial therapy dramatically reduces morbidity and mortality (which can reach 5–10 % for untreated pneumonic or typhoidal forms).

First‑Line Antibiotics

• Streptomycin 1 g IM/IV every 12 h for 10–14 days (CDC/WHO preferred).
• Gentamicin 5 mg/kg IV/IM daily for 10–14 days (alternative to streptomycin).

Oral Options (mild to moderate disease)

• Doxycycline 100 mg PO twice daily for 14–21 days.
• Ciprofloxacin 500 mg PO twice daily for 14–21 days.

Supportive Care

• Antipyretics (acetaminophen or ibuprofen) for fever and aches.
• Fluid replacement if dehydrated.
• Analgesics for ulcer pain.
• Drainage of suppurative lymph nodes by a qualified clinician, if needed.

Special Situations

• Pregnancy: Gentamicin is preferred; doxycycline is contraindicated.
• Severe pneumonic disease: Hospitalization, IV antibiotics, and possible mechanical ventilation.
• Immunocompromised patients: Longer treatment courses (≥21 days) and close monitoring.

Living with Rabbits Fever (Tularemia)

Even after successful treatment, some individuals experience lingering effects. Below are practical tips for daily life.

• Follow up with your provider after completing antibiotics to ensure full resolution.
• Monitor wound healing – keep ulcer sites clean; use sterile gauze; watch for increasing redness or drainage.
• Maintain hydration and nutrition to support immune recovery.
• Gradual return to activity – avoid heavy lifting or strenuous exercise for at least 2 weeks after fever subsides.
• If you work in an at‑risk occupation, inform your employer about your diagnosis; they may need to implement additional safety measures.
• Consider a vaccination trial if you belong to a high‑risk group; a live attenuated vaccine exists for laboratory personnel in some countries (not widely available for the public).

Prevention

Because exposure is linked to specific activities, targeted prevention is effective.

Personal Protective Measures

• Wear gloves and long sleeves when handling wildlife, carcasses, or soil in endemic areas.
• Use protective eyewear if there is a risk of splashes to the eyes.
• Avoid direct contact with dead animals; if unavoidable, disinfect skin promptly with soap and water.
• Use insect repellents (DEET, picaridin) and wear tick‑protective clothing.
• Perform thorough tick checks after outdoor work.

Environmental Controls

• Keep lawns and brush trimmed to reduce rodent and tick habitats.
• Discourage feeding or attracting wild rabbits near homes.
• Use protective masks (N95 or higher) when mowing or disturbing soil that may aerosolize dust.
• Drink only treated or boiled water from natural sources.

Food Safety

• Cook wild game to an internal temperature of at least 71 °C (160 °F).
• Freeze meat for ≥48 h at –20 °C before cooking, which reduces bacterial load.

Vaccination & Post‑Exposure Prophylaxis

Currently, no licensed commercial vaccine is available for the general public. In the United States, a live attenuated vaccine is reserved for laboratory workers under an investigational protocol. If you suspect recent exposure, a single dose of doxycycline 200 mg within 72 hours may be recommended as prophylaxis (CDC guidance).

Complications

Without timely treatment, tularemia can lead to serious, sometimes life‑threatening complications.

• Pneumonia – can progress to respiratory failure.
• Septicemia – systemic infection leading to organ dysfunction.
• Encephalitis – rare but possible with typhoidal disease.
• Chronic lymphadenitis – persistent swollen nodes that may need surgical drainage.
• Vision loss in oculoglandular cases if not promptly treated.
• In pregnant women, infection can cause miscarriage or preterm labor.

When to Seek Emergency Care

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Sources: CDC – Tularemia (2023); WHO – Tularemia Fact Sheet (2022); Mayo Clinic – Tularemia Overview (2024); Cleveland Clinic – Tularemia Treatment (2023); National Institutes of Health (NIH) – Francisella tularensis research articles; Peer‑reviewed journals: Clinical Infectious Diseases, Emerging Infectious Diseases.

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