Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

Cat Bites and Cat-Scratch Disease

Cat bites and cat-scratch disease are both associated with cats, but they are two distinct clinical entities.

1. Cat Bites

Epidemiology

• Cat bites have a relatively high infection rate, approximately 30–50%.
• Dog bites are more common overall but have a lower infection rate.
• Cat bites are more common in females.
• Animal bites are common in children.
• Cat bites commonly involve the upper extremity, particularly the hand.
• Presentation may be delayed because the initial puncture wound is often underestimated.

Why Cat Bites Are Highly Infectious

Cats have small, sharp, needle-like teeth that can produce deep puncture wounds.

The puncture may penetrate:

• Bone
• Joint
• Tendon sheath

The skin may seal rapidly over the puncture, making the injury appear deceptively minor.

This can result in:

• Septic arthritis
• Tenosynovitis
• Osteomyelitis
• Abscess

Risk Factors for Infection

Risk increases with:

• Treatment delayed beyond 12 hours
• Older age
• Puncture wounds
• Diabetes
• Immunosuppression

Causative Organisms

The lecture identifies Pasteurella as the most common organism.

• Present in approximately 80% of cat bites
• Infection is often polymicrobial
• Pasteurella can produce significant pain and swelling within approximately 48 hours
• Culture may take several days to grow

Early Treatment

For an early presentation:

• Irrigation
• Wound care
• Tetanus prophylaxis as appropriate
• Splinting when necessary
• Antibiotics when indicated
• Observation

Antibiotics

The lecture specifically identifies amoxicillin-clavulanate (Augmentin) as the commonly used antibiotic.

Antibiotics are particularly emphasized for:

• Hand injuries
• Facial injuries
• Severe or deep wounds
• Wounds extending toward bone

The lecture describes a 3–5 day course for prophylaxis.

Delayed Presentation

Delayed treatment can result in:

• Abscess
• Septic arthritis
• Tenosynovitis
• Osteomyelitis

These patients may require:

• Surgical incision and drainage
• Debridement/cleaning of the wound
• Antibiotic treatment

A significant proportion of cat-bite patients requiring surgery is noted in the lecture.

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2. Cat-Scratch Disease

Cat-scratch disease is different from a cat bite infection.

It is an infection transmitted through a cat scratch and is associated with Bartonella species.

Clinical Course

The typical course is:

Cat scratch-

Within approximately 1 week

Small skin lesion-

Within approximately 2 weeks

Regional lymph-node enlargement

The skin lesion is usually:

• Small
• Less than approximately 1 cm

The disease is generally self-limiting, with symptoms lasting several weeks.

Clinical Features

Important symptoms include:

• Regional lymphadenopathy
• Fever
• Fatigue
• Headache
• Tender or enlarged lymph nodes
• Occasionally draining lymph nodes

The key clinical feature is:

Regional lymphadenopathy following exposure to a cat.

Common Lymph-Node Groups

Depending on the site of inoculation, lymphadenopathy may occur in:

• Cervical nodes
• Axillary nodes
• Epitrochlear nodes
• Inguinal nodes

Enlarged nodes can sometimes be mistaken for a soft-tissue tumour.

Therefore, cat-scratch disease should be considered in the differential diagnosis of an unexplained regional mass.

Investigations

The lecture mentions:

• ESR
• CRP
• Testing for cat-scratch disease

It also notes that biopsy is generally unnecessary.

If performed, biopsy may demonstrate:

• Lymphoid tissue
• Necrotizing granulomatous inflammation

Treatment

The lecture describes the disease as generally self-limiting.

Antibiotics mentioned include:

• Azithromycin
• Ciprofloxacin
• Doxycycline

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Cat Bite vs Cat-Scratch Disease

Feature	Cat bite	Cat-scratch disease
Mechanism	Bite/puncture	Scratch
Main problem	Local bacterial infection	Regional lymphadenopathy
Important organism	Pasteurella	Bartonella
Wound	Deep puncture	Small skin lesion
Major complications	Septic arthritis, tenosynovitis, osteomyelitis	Usually self-limiting lymphadenopathy
Typical timing	Infection can develop rapidly	Skin lesion followed by nodes over 1–2 weeks
Treatment	Wound care + antibiotics when indicated	Often self-limiting; antibiotics in selected cases

High-Yield Points

• Cat bite is not the same as cat-scratch disease.
• Cat bites have a high risk of infection because the teeth produce deep puncture wounds.
• Pasteurella is the important organism emphasized for cat bites.
• A seemingly small cat bite to the hand can involve the tendon sheath or joint.
• Delayed treatment increases the risk of tenosynovitis, septic arthritis and osteomyelitis.
• Amoxicillin-clavulanate is the antibiotic highlighted in the lecture.
• Cat-scratch disease is associated with Bartonella.
• Regional lymphadenopathy after a cat scratch is the characteristic clinical clue.
• Cat-scratch disease is generally self-limiting.
• Enlarged epitrochlear or other regional lymph nodes can mimic a soft-tissue tumour.