Rabbit Fever (Tularemia)

Rabbit Fever (Tularemia): Symptoms, Causes, Types, Diagnosis, and Treatments

Rabbit Fever, scientifically known as tularemia, is a rare but potentially serious infectious disease caused by the bacterium Francisella tularensis. Despite its name, Rabbit Fever is not exclusive to rabbits; it can affect a wide range of wild and domestic animals and can be transmitted to humans in various ways.

This comprehensive guide explores the nature of Rabbit Fever, its symptoms, causes, transmission routes, types, diagnostic methods, and treatment options. Understanding this disease is essential for prompt medical intervention and effective prevention strategies.

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What is Rabbit Fever?

Rabbit Fever or tularemia is a zoonotic disease, meaning it is transmitted from animals to humans. It is caused by the Francisella tularensis bacterium, which exists in nature in various forms. This disease primarily affects rabbits, hares, rodents, and other small mammals. Humans usually get infected through tick or deer fly bites, handling infected animals, ingesting contaminated food or water, or inhaling aerosols containing the bacteria.

While rare, tularemia can be very serious and potentially fatal if left untreated. However, with early diagnosis and proper antibiotic treatment, the prognosis is typically good.

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History and Epidemiology

Tularemia was first identified in 1911 in Tulare County, California — hence the name. It became more widely studied after an outbreak among squirrels. The causative organism, Francisella tularensis, is named after Dr. Edward Francis, who conducted early research on the disease.

Though cases are rare, tularemia is found across North America, Europe, and parts of Asia. In the United States, the Centers for Disease Control and Prevention (CDC) reports several hundred cases each year, with higher incidence in southern and central states, particularly Arkansas, Missouri, and Oklahoma.

Tularemia is also considered a potential bioterrorism agent due to its high infectivity and ability to be aerosolized.

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Causes and Transmission

Causative Agent

The disease is caused by a gram-negative bacterium called Francisella tularensis, which has several subtypes, but the most virulent strains are Type A (common in North America) and Type B (found in Europe and Asia).

Modes of Transmission

Humans can become infected through:

1. Bites of Infected Arthropods: Ticks (especially dog ticks and wood ticks), deer flies, and mosquitoes can carry the bacteria and transmit it through bites.
2. Direct Contact: Handling infected animals (especially rabbits and rodents), particularly during skinning or butchering, can result in skin transmission.
3. Inhalation: Breathing in dust or aerosols contaminated with the bacterium, often during farming, landscaping, or laboratory exposure.
4. Ingestion: Drinking contaminated water or eating undercooked infected meat.
5. Contaminated Environments: Touching infected surfaces, soil, or plant matter.

Is Tularemia Contagious?

Tularemia is not known to spread from person to person, making it different from many other bacterial infections.

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Types of Rabbit Fever

There are several clinical forms of tularemia, depending on how the bacteria enter the body:

1. Ulceroglandular Tularemia

• Most common form
• Occurs through skin contact with infected animals or insect bites
• Characterized by skin ulcers and swollen lymph nodes

2. Glandular Tularemia

• Similar to ulceroglandular but without skin ulcers
• Often acquired via tick or deer fly bites

3. Oculoglandular Tularemia

• Occurs when the bacteria enter through the eye
• Causes conjunctivitis, eye pain, and swollen lymph nodes near the ear or jaw

4. Oropharyngeal Tularemia

• Caused by eating contaminated food or water
• Symptoms include sore throat, mouth ulcers, tonsillitis, and abdominal pain

5. Pneumonic Tularemia

• Most serious form
• Results from inhaling the bacteria
• Leads to cough, chest pain, and difficulty breathing

6. Typhoidal Tularemia

• Rare and systemic
• Presents with generalized symptoms like fever and fatigue without specific local signs
• Can become fatal without treatment

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Signs and Symptoms

Symptoms of Rabbit Fever typically appear 3 to 5 days after exposure but can take up to 14 days. The presentation varies by type but common symptoms include:

• Sudden fever (up to 104°F or 40°C)
• Chills
• Headache
• Fatigue or malaise
• Muscle aches
• Swollen lymph nodes
• Skin ulcers at the site of infection
• Sore throat (oropharyngeal)
• Eye inflammation (oculoglandular)
• Chest pain, cough, and difficulty breathing (pneumonic form)
• Gastrointestinal symptoms (diarrhea, nausea, vomiting)

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Complications of Tularemia

If untreated or improperly managed, tularemia can lead to severe complications, especially in vulnerable individuals such as children, the elderly, and those with weakened immune systems. Potential complications include:

• Pneumonia
• Meningitis
• Liver damage
• Infection spreading to bones or joints
• Sepsis, a life-threatening body-wide infection

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Diagnosis

Prompt diagnosis is crucial due to the disease’s rapid progression. However, tularemia can mimic many other illnesses, which makes diagnosis challenging.

Medical History and Physical Examination

Physicians will inquire about:

• Exposure to wildlife or tick bites
• Occupation (e.g., farmers, hunters, lab workers)
• Travel history
• Symptom timeline

Laboratory Tests

• Blood Tests: Detect elevated white blood cells and inflammatory markers.
• Serologic Tests: Identify specific antibodies to Francisella tularensis.
• Polymerase Chain Reaction (PCR): Detect bacterial DNA from blood, sputum, or tissue samples.
• Culture: Though definitive, cultures must be handled in biosafety labs due to biohazard risks.

Imaging

Chest X-rays or CT scans may be needed in pneumonic tularemia to evaluate lung involvement.

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Treatment Options

Tularemia responds well to antibiotics when treated early. Hospitalization is sometimes required for severe forms.

Antibiotics

The most effective antibiotics for treating Rabbit Fever include:

• Streptomycin: The first-choice drug, especially for severe infections
• Gentamicin: An alternative to streptomycin, often administered intravenously
• Doxycycline: Oral option for mild to moderate cases
• Ciprofloxacin: Another effective oral antibiotic

Supportive Care

• Fever reducers like acetaminophen
• Fluids and electrolytes for dehydration
• Respiratory support for severe pneumonic cases

Duration of Treatment

Typically, the antibiotic course lasts 10–21 days, depending on the form and severity. Follow-up is essential to monitor for relapse or complications.

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Prevention

Since there is no vaccine currently approved for the general public, prevention relies on minimizing exposure to the bacterium.

Personal Protection

• Use insect repellents containing DEET
• Wear gloves when handling wild animals
• Avoid drinking untreated water from natural sources
• Cook meat thoroughly
• Use protective masks if working in high-risk areas like farms or labs

Environmental Control

• Control rodent populations
• Reduce tick habitats by clearing brush and grass
• Properly dispose of animal carcasses

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FAQs About Rabbit Fever

Q1: Can Rabbit Fever be deadly?

Yes, if untreated, tularemia can be fatal, particularly the pneumonic and typhoidal forms. However, with appropriate antibiotics, mortality rates drop significantly.

Q2: How common is tularemia?

It is a rare disease, with only a few hundred cases reported annually in the U.S., but it’s more common in rural or outdoor settings.

Q3: Can pets get tularemia?

Yes, cats, dogs, and especially outdoor pets may contract the disease and potentially transmit it to humans via contact.

Q4: Is there a vaccine for Rabbit Fever?

A live-attenuated vaccine exists but is currently not licensed for general public use. It is used experimentally for lab workers at risk.

Q5: Is tularemia a bioterrorism concern?

Yes. Due to its infectious nature, ease of aerosol transmission, and lack of immunity in the general population, it is classified as a Category A bioterrorism agent.

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Conclusion

Rabbit Fever, or tularemia, is a serious but treatable infection that should not be taken lightly. Caused by Francisella tularensis, this disease can manifest in various forms depending on the route of infection, from skin ulcers to severe pneumonia. Though rare, it has significant public health importance due to its zoonotic nature and potential use as a biological weapon.

Prompt recognition of symptoms, early diagnosis, and timely antibiotic therapy are critical for a positive outcome. Preventive measures, especially for those frequently in contact with wildlife or rural environments, can significantly reduce the risk of infection.

Frequently Asked Questions (FAQs) About Rabbit Fever (Tularemia)

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