Cat scratch fever overview

# Overview
Cat scratch fever is a usually benign infectious disease caused by the intracellular parasite Bartonella.  It is most commonly found in children 1-2 weeks following a cat scratch. 
The cats serve as the natural reservoir for B.henselae.

# Historical Perspective
It was first described in 1889 by Henri Parinaud.  The cat was recognized as the vector of the disease in 1931 by Dr. Robert Debre.

# Pathophysiology
The causative organism was first thought to be Afipia felis, but this was disproved by immunological studies demonstrating that cat scratch fever patients developed antibodies to two other organisms, Bartonella henselae and Bartonella clarridgeiae, which are rod-shaped Gram negative bacteria.
Cat scratch disease can be transmitted from a scratch or bite from an infected cat, as well as from exposure to cat fleas. The breach in the skin or mucosal surfaces (eg, mouth and eyes) if comes in contact with infected cat saliva can lead to the spread of the disease.
B. henselae causes an acute inflammatory reaction associated with activation of a proinflammatory cascade following invasion of endothelial cells.
Ticks are also a major transmitter of this disease.  It is often transmitted at the same time a human may get Lyme disease.  It is often missed when people are tested and diagnosed for Lyme disease as the symptoms can be similar, such as fatigue, and headaches.

# Risk Factors
People having cats as pet at are higher risk of getting the disease.
Immunosuppression leads to the disseminated form of the disease.

# Diagnosis
Most cases of Cat scratch disease are clinically diagnosed.
To confirm the clinical impression serologic testing including enzyme immunoassay (EIA) or indirect fluorescence assay (IFA) are performed.
High titers (greater than 1:256) of immunoglobulin G antibody to Bartonella are diagnostic.
Lymph node or tissue biopsy is rarely done.
Polymerase chain reaction (PCR) tests for Bartonella on tissue or blood are also available.

## Symptoms
Cat scratch fever is a usually benign infectious disease caused by the intracellular parasite Bartonella.  It is most commonly found in children 1-2 weeks following a cat scratch.
The most common manifestation is tender lymphadenopathy 
The most commonly involved lymph nodes are the axillary, epitrochlear, submandibular, cervical, and supraclavicular lymph nodes.
Visceral involvement is more commonly seen in children infected with the symptoms of fever and abdominal pain manifesting as hepatomegaly, splenomegaly.
Ocular symptoms include optic neuritis and parinaud oculoglandular syndrome( tender regional lymphadenopathy of the preauricular or cervical lymph nodes associated with conjunctivitis or eyelid infection )
Neuroretinitis seen rarely in pateints.

## Laboratory Findings
A simple blood test can test for the presence of antibodies for Bartonella.  It can be quite common for someone to have Lyme disease, Babesia and Bartonella from a single tick bite.

# Treatment

## Medical Therapy
Most healthy people will clear the infection without treatment, and antimicrobial therapy is not recommended for immunocompetent patients with mild to moderate Bartonella henselae disease due to the risk of side-effects from antibiotics.  Azithromycin, ciprofloxacin, doxycycline, and multiple other antibiotics have been used but with unclear benefit.
Azithromycin is preferentially used in pregnancy to avoid the side-effects of doxycycline.
Corticosteroids are given for a persistent disease.
Needle aspiration of suppurative lymph nodes can also be performed.