Cat Scratch Fever: Symptoms, Types, Causes and Treatment

Cat scratch fever, also known as cat scratch disease (CSD), is a fascinating yet often misunderstood zoonotic infection. Most commonly affecting children and young adults, this illness is typically triggered by a seemingly harmless encounter with a playful kitten or cat. While many people recover with little intervention, some experience surprisingly complex or even severe symptoms. This article takes a comprehensive look at the symptoms, types, causes, and treatments of cat scratch fever, drawing on the latest scientific findings and clinical observations.

Symptoms of Cat Scratch Fever

Cat scratch fever can range from mild and fleeting discomfort to persistent and occasionally serious illness. Understanding the array of symptoms is crucial for early recognition and proper management.

Symptom	Description	Onset/Duration	Source(s)
Lymphadenopathy	Swollen, tender lymph nodes (often unilateral)	1–4 weeks post-scratch	2 3 6 10
Fever	Low to moderate, sometimes prolonged	Often with lymphadenopathy	2 3 6 9 10
Malaise	General feeling of unwellness	Early in illness	2 3
Skin Lesion	Papule or pustule at scratch/bite site	Days after injury	3 4
Atypical Symptoms	Hepatosplenic lesions, neuroretinitis, bone pain	Variable, especially in atypical cases	5 6 9 13

Table 1: Key Symptoms

Classic Symptoms

The hallmark of cat scratch fever is swollen, tender lymph nodes (lymphadenopathy), often near the site of a cat scratch or bite. This is usually accompanied by low-grade fever and feelings of malaise. In many cases, a small, red papule or pustule develops at the site of injury days before the lymph nodes swell 2 3 6 10.

Key features:

• Lymphadenopathy is most often unilateral (affecting one side), commonly found in the cervical (neck) or axillary (armpit) regions 6.
• The enlarged lymph node may be particularly noticeable or even "impressive" 2.
• Fever occurs in 30–50% of patients and tends to be mild and self-limited 6 9.

Skin and Systemic Manifestations

Most cases of CSD are mild, but some individuals develop additional symptoms:

• Erythema nodosum (tender red nodules, usually on the shins) is the most common skin manifestation after the initial papule 3.
• Less common presentations include papulovesicular eruptions, maculopapular rashes, and erythema multiforme 3.
• Systemic symptoms such as headache, muscle aches, and prolonged fever may occur, especially in atypical or disseminated cases 5 9.

Severe or Atypical Presentations

In rare cases, particularly in immunocompromised individuals or children, CSD can cause:

• Hepatosplenic lesions (microabscesses in the liver and spleen), leading to abdominal pain and prolonged fever 6 9 13.
• Neuroretinitis (inflammation of the optic nerve and retina), resulting in visual disturbances 6.
• Bone involvement (osteolytic lesions, osteomyelitis) and persistent fever of unknown origin 1 5 6 9.
• Multiorgan involvement including the central nervous system or heart (endocarditis), most often in immunosuppressed patients 5 11.

Types of Cat Scratch Fever

Cat scratch fever is not a one-size-fits-all illness. Clinicians recognize several distinct types, ranging from the typical self-limited form to rare but serious disseminated disease.

Type	Primary Features	Typical Population	Source(s)
Typical (Classic)	Lymphadenitis, mild fever, local lesion	Children, young adults	2 3 6 10
Atypical	Prolonged fever, hepatosplenic, neuroretinitis, bone lesions	Children, immunocompromised	5 6 9 13
Systemic	Multiorgan involvement—liver, spleen, CNS	Immunocompromised, severe pediatric cases	5 9 13
Oculoglandular	Parinaud oculoglandular syndrome (eye redness, lymphadenitis)	All ages	11

Table 2: Types of Cat Scratch Fever

Typical (Classic) Cat Scratch Fever

The majority of CSD cases fall into this category. Key features include:

• Localized, unilateral lymph node swelling, usually near the site of cat injury 2 6 10.
• Mild systemic symptoms: low-grade fever, malaise, headache 2 3.
• Most patients recover without intervention, and complications are rare 3 6.

Atypical Cat Scratch Fever

Roughly 20–25% of cases can be considered atypical, with presentations including:

• Prolonged fever (lasting weeks) without clear cause 6.
• Hepatosplenic disease: microabscesses or lesions in the liver and spleen, leading to abdominal pain and prolonged fever 6 9 13.
• Neuroretinitis: vision changes due to inflammation of the optic nerve and retina 6.
• Bone lesions: pain and swelling if bones are affected 1 6.
• These forms are more common in immunocompromised individuals and may require more aggressive treatment 5 6 9.

Systemic and Disseminated Disease

Rarely, CSD spreads beyond regional lymph nodes, causing:

• Multiple organ involvement (liver, spleen, bones, central nervous system) 5 9.
• Severe, persistent symptoms such as prolonged fever, weight loss, and multi-system involvement 5 9 13.
• Higher risk in individuals with compromised immune systems (e.g., those on immunosuppressive therapy) 5 11.

Oculoglandular Syndrome

Parinaud oculoglandular syndrome is a specific form involving:

• Eye redness, pain, and swelling, often with preauricular lymphadenopathy 11.
• Usually follows direct inoculation of the eye with contaminated material.

Causes of Cat Scratch Fever

Understanding what causes cat scratch fever—and how it spreads—is essential, both for prevention and for unraveling the puzzle when someone falls ill.

Cause	Description	Transmission Route	Source(s)
Bartonella henselae	Gram-negative bacterium; main cause	Cat scratch, bite, saliva	4 5 6 7 10 11
Bartonella clarridgeiae	Less common Bartonella species	Cat bite or scratch	7
Cat Contact	Exposure to kittens or cats	Direct contact	2 6 10
Immunity	Immunocompromised at higher risk	N/A	4 5 11

Table 3: Causes of Cat Scratch Fever

The Main Culprit: Bartonella henselae

• Overwhelmingly, cat scratch fever is caused by the bacterium Bartonella henselae, a fastidious, gram-negative rod 4 5 6 10 11.
• This bacterium is commonly found in young cats and kittens, which can carry the organism without showing symptoms 6 10.
• Transmission occurs via cat scratches, bites, or when cat saliva comes into contact with broken skin 4 10.
• Children and young adults are most frequently affected, possibly due to closer contact with pets 6.

Other Bartonella Species

• Bartonella clarridgeiae has also been implicated as a less common cause of CSD, identified in both cats and humans 7.
• The clinical presentation is similar, with fever and lymphadenopathy following a scratch or bite 7.

Modes of Transmission

• Direct contact with cats, especially kittens, is the main risk factor 2 6 10.
• Scratches and bites are the classic routes, but even a lick on a broken area of skin can transmit the bacteria 4 10.
• Not every person with cat exposure will develop CSD, indicating that host factors and immune response play a role 4 5 11.

Role of Immunity

• Healthy individuals typically experience mild disease 4 6.
• Immunocompromised patients (e.g., those with HIV/AIDS, cancer, or on immunosuppressive therapy) are at higher risk for severe, disseminated forms of CSD, including multiorgan involvement and unusual complications 4 5 11.

Treatment of Cat Scratch Fever

While cat scratch fever often resolves on its own, some patients—especially those with severe or atypical disease—require targeted therapy. The approach to treatment is tailored to the individual and the severity of symptoms.

Treatment	Indication	Effectiveness/Outcome	Source(s)
Supportive Care	Typical, mild cases	Usually sufficient; self-limited	3 6 11 12
Azithromycin	Moderate, severe, or persistent cases	Accelerates resolution of lymphadenopathy	4 5 11 14
Rifampin	Hepatosplenic/systemic disease	High efficacy in severe cases	5 11 12 13
TMP-SMX	Alternative antibiotic	Effective in some cases	12 14
Doxycycline	Severe or atypical presentations	Used, especially in adults	4 5 10
Gentamicin	Severe/disseminated cases	Effective as adjunct	11 12 13
Corticosteroids	Refractory inflammatory disease	Occasionally used for persistent fever	15

Table 4: Treatment Approaches

Supportive and Conservative Management

• Most cases of classic cat scratch fever are mild and resolve without antibiotics 3 6 11 12.
• Rest, pain relief, and warm compresses to swollen lymph nodes are usually sufficient 3 6.
• Observation is recommended for otherwise healthy patients with mild symptoms 6 11.

Antibiotic Therapy

Antibiotics may shorten the duration and severity of symptoms, especially in moderate or severe cases.

First-line agents:

• Azithromycin: Shown in clinical trials to speed the reduction in lymph node size and hasten symptom resolution 4 5 11 14.
• Rifampin: Particularly effective in hepatosplenic or systemic disease; rapid improvement noted in pediatric studies 5 12 13.
• Trimethoprim-sulfamethoxazole (TMP-SMX): A reasonable alternative, especially if azithromycin cannot be used 12 14.
• Doxycycline: Used in adults and for complicated cases; often combined with other agents 4 5 10.
• Gentamicin: Reserved for severe, atypical, or disseminated CSD, usually in combination with other antibiotics 11 12 13.

Effectiveness:

• Not all antibiotics are equally effective; studies highlight rifampin, ciprofloxacin, TMP-SMX, and gentamicin as the most beneficial for severe disease 12.
• In mild cases, antibiotics may offer little additional benefit 3 11 12.

Special Situations

• Atypical or systemic CSD (e.g., with liver, spleen, bone, or CNS involvement) requires prompt and aggressive antibiotic therapy, sometimes in combination 5 9 13.
• Immunocompromised patients need close monitoring and a lower threshold for initiating treatment 4 5 11.
• Corticosteroids have been used in select refractory cases (e.g., persistent fever despite antibiotics or severe inflammatory complications) 15.

Diagnosis and Monitoring

• Diagnosis is based on clinical history (cat exposure, symptoms), supported by serology and, in complex cases, molecular techniques such as PCR or metagenomic next-generation sequencing 4 10.
• Imaging (ultrasound, CT) may be required for atypical or systemic disease to assess organ involvement 6 9 13.

Conclusion

Cat scratch fever is a common yet complex zoonotic disease, most often resulting in self-limited lymphadenopathy but capable of causing a wide range of clinical presentations. While most cases in healthy individuals are mild and resolve without treatment, awareness of atypical forms—especially in children and immunocompromised patients—is vital for timely diagnosis and management.

Main points covered:

• Cat scratch fever usually presents with swollen lymph nodes, fever, and a lesion at the site of a cat scratch or bite.
• Most cases are mild, but atypical and systemic forms can cause severe or prolonged illness, particularly in vulnerable populations.
• The primary cause is Bartonella henselae, with B. clarridgeiae as a rare alternative.
• Treatment is largely supportive for mild cases, with antibiotics (azithromycin, rifampin, TMP-SMX, doxycycline, gentamicin) reserved for severe or complicated disease.
• Careful clinical evaluation and tailored treatment are essential, especially for those with atypical symptoms or compromised immunity.

Understanding cat scratch fever empowers both patients and healthcare providers to recognize, manage, and, when possible, prevent this intriguing infection.