What is Cat Scratch Fever?

Cat scratch disease is an infectious disease caused by Hansebar's body invading the human body after being scratched and bitten by a cat. The clinical manifestations are variable. However, it is mainly characterized by local skin lesions and lymphadenopathy in the drainage area.

Basic Information

English name

cat-scratch disease

Visiting department

Infectious Diseases

Common locations

Hands, forearms, feet, calves, face, eyes, etc.

Common causes

Caused by Hansebal's body after being scratched and bitten by a cat

Common symptoms

Erythematous papules, fever, fatigue; anorexia, nausea, vomiting, abdominal pain, etc.

Causes of cat scratch disease

Hansenba is a slim, polymorphic coryneform bacterium, (0.3 1.0) m × (0.6 3.0) m in size, negative for Gram stain and negative for oxidase. It is an aerobic bacterium with severe nutritional requirements. Slow growth in culture. Hanseatic is found in the oropharynx of cats, and fleas are a vector for cat populations. Humans are transferred to the human body by scratching, biting, or close contact of the cat with the cat, causing human infection.

Clinical manifestations of cat scratch disease

Diversified, but mostly mild cases, the clinical manifestations are as follows:

Primary skin lesions

One or several erythematous pimples appear locally after being caught and bitten by a cat, and the pain is not significant; a small number of papules turn into blisters or pustules, which can be punctured to form small ulcers, leaving short pigmentation or crusting after 1 to 3 weeks More. Skin lesions are more common in the hands, forearms, feet, calves, face, eyes, etc., and can be ignored due to mild symptoms.

2. Local lymphadenopathy

One to two weeks after the infection, the lymph nodes in the drainage area are enlarged, which are common in the head and neck, axilla, and groin. The texture is firm in the early stage, with painful touch, the size is 1-8cm, the lymph nodes are purulent, and occasionally puncture to form a sinus or fistula. Swollen lymph nodes usually resolve on their own within 2 to 4 months, and a few continue for several months. Swollen lymph nodes are seen in adjacent and even whole body lymph nodes.

3. Systemic symptoms

Most of them have mild fever and fatigue; anorexia, nausea, vomiting, abdominal pain and other gastrointestinal symptoms accompanied by weight loss; headache, splenomegaly, sore throat, and conjunctivitis. Conjunctivitis with swollen lymph nodes in the ear is an important feature of cat scratch disease.

4. Rare manifestations and complications

Rare clinical manifestations and complications include encephalopathy, chronic severe organ damage, and joint disease. Other transient maculopapular rash, erythema polymorpha, thrombocytopenic purpura, parotid enlargement, multiple hemangiomas, and visceral purpura are all occasional.

Encephalopathy is often manifested clinically as encephalitis or meningoencephalitis, which occurs 1 to 6 weeks after lymphadenopathy. The condition is generally mild and recovers quickly. Lymphocytes and proteins in cerebrospinal fluid are normal or slightly increased. Symptoms of severely ill patients often last for several weeks, and may be accompanied by coma and convulsions, but most of them recover completely within 1 to 6 months, occasionally causing disability or death.

Cat scratch disease check

1. Pathogen culture and isolation

The Hanseba body was isolated and cultured from the patient's blood, lymph node pus, and primary skin lesions, and the diagnosis was positive.

2. Immunological examination

(1) The indirect immunofluorescent antibody test (IFA) was used to determine Hansebaton body-specific antibodies in the patient's serum, and the titer 1:64 was positive. Early in the course of the disease and more than 4 to 6 weeks, the titer of the two serums increased by more than 4 times, which is also meaningful for diagnosis. This test is a simple, fast, sensitive, and specific method for the diagnosis and diagnosis of this disease.

(2) Enzyme-linked immunosorbent assay (ELISA-IgM) is used to detect anti-Hansebaton body IgM antibody, which has strong sensitivity, specificity and clinical diagnostic value. ELISA-IgG antibodies are less sensitive and cannot be used as laboratory diagnostic criteria.

(3) The skin test uses the lymph node puncture solution as the antigen after heat sterilization. 0.1 ml of the antigen is injected intradermally into the palm of the forearm. 48 hours after the occurrence of induration with a diameter of 5mm, the patient is positive. It usually exists for 48 hours, and the induration can last for 5-6 days or 4 weeks. The skin test is a late-type allergy, which is more sensitive and specific, and its false positive is about 5%. Repeatedly two times at intervals of 4 weeks and still negative can exclude cat scratch diagnosis. Positive skin test after infection can be maintained for more than 10 years.

3. Molecular biology testing

In recent years, PCR, nested PCR, or PCR in situ hybridization techniques have been used to detect Hansebastosoma DNA from lymph node biopsy specimens and pus. However, this method with high specificity and sensitivity requires high experimental conditions and is difficult to be used as a routine clinical examination.

4. Histopathological examination

Warthin-Starry and Brown-Hopps tissue staining or tissue electron microscopy of biopsy tissues found that polymorphic Gram-negative pathogens were found in tissue cells to help diagnosis. However, tissue staining cannot distinguish between different bacterial types or other pathogens of Bartonella.

5. Blood routine

In the early course of the disease, the total number of white blood cells decreased, the white blood cell count increased slightly when the lymph nodes were purulent, the neutrophil count increased, and the blood sedimentation increased.

Cat scratch diagnosis

The disease can be diagnosed based on the patient's cat and dog contact, scratch and bite history, staining method, skin test, and serum test.

Differential diagnosis of cat scratch disease

Mainly related to various causes such as EB virus infection, Mycobacterium infection, Staphylococcus infection, hemolytic streptococcus infection, STD (syphilis, soft chancre, STD lymphogranuloma, etc.), toxoplasmosis, gangrene, rabbit Lymph node enlargement or (and) suppuration due to fever, rat bite fever, tsutsugamushi disease, sarcoidosis, sarcoidosis, brucellosis, malignant or benign lymphoma, Kawasaki disease, etc. Lesions with swollen lymph nodes in front of the ear often indicate cat scratch disease.

Cat scratch disease treatment

The disease is mostly self-limiting, and usually heals within 2 to 4 months. Treatment is mainly symptomatic. When the lymph nodes are purulent, puncture and suction can be performed to reduce the symptoms. Repeat if necessary after 2 to 3 days. Should not be cut open drainage. Symptoms of lymphadenopathy that have not been reduced for more than one year may be considered surgical removal.

Although Hanseba in vitro is sensitive or highly sensitive to many antibacterial drugs and their derivatives, aminoglycosides, rifampicin, ciprofloxacin, etc., there is no indication of antibacterial drugs in general cases. For severe diseases such as high fever, encephalitis and immunodeficiency (HIV infection, etc.), antibiotics should be used in a timely manner, and the clinical time is generally more than 2 weeks.

Cat scratch disease prognosis

The prognosis is good. Except for those with severe encephalopathy, it is rarely fatal, with a mortality rate of <1%. When the lymphadenopathy is larger than 5cm, the swelling usually lasts 1 to 2 years.