Cat scratch disease: causes, symptoms, diagnosis, treatment

Cat scratch disease (felinosis, benign lymphoreticulosis) is an acute zoonotic infectious disease with contact and transmission mechanisms of the pathogen, characterized by lymphadenitis, primary affect in the form of a suppurating papule, in some cases - conjunctivitis, angiomatosis and liver damage.

ICD 10 code

A28.1. Cat scratch fever.

Epidemiology of cat scratch disease

The source of the pathogen for humans is cats, most often kittens. Cats are easily infected with B. henselae through bites of Cfenocephalides felis fleas. In the cat's body, B. henselae persists for more than a year without causing health problems and is part of the normal microflora of the oral cavity. Cats may have asymptomatic bacteremia lasting up to 17 months (observation period), which stops after a course of antibiotic therapy. Humans become infected during close contact with a cat (bite, scratch, lick) when the skin or conjunctiva of the eye is damaged. Fleas can also attack humans, transmitting the disease. Approximately 90% of those infected have a history of contact with cats; contacts with squirrels, dogs, goats, crab claw pricks, and barbed wire have also been described. Susceptibility is low.

Children and people under 20 usually get sick, more often in autumn and winter. Sometimes family outbreaks occur. Patients do not pose a danger to others. After the disease, a strong immunity develops, but relapses of the disease in adults have been described.

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What causes cat scratch disease?

Cat scratch disease is caused by Bartonella henselae B. quintanae of the Bartonella family is a mobile, small, gram-negative, round rod measuring 0.3-0.5x1.0x3.0 µm. It has one flagellum and is capable of intracellular parasitism.

In sections of infected tissues, the rods may be curved, pleomorphic, and often grouped into compact clusters. They are stained according to Romanovsky-Giemsa, and in tissue biopsies - with dyes using silver (according to Warthing-Starry). In immunochemical studies, acridine orange dye is used. The bacteria have a clearly structured three-layer membrane containing up to 12 proteins with a molecular weight of 28-174 kDa. Reproduction of the pathogen occurs by simple transverse division.

B. henselae can be cultivated outside the human body in cat fleas, as well as in semi-liquid or solid nutrient media enriched with 5-10% human or animal blood (this requires long-term, more than 15-45 days, maintenance of seeded agar plates under optimal conditions).

The pathogenicity factors of B. henselae have not been studied.

Pathogenesis of cat scratch disease

The pathogen spreads from the entry point lymphogenously and hematogenously. B. henselae first attach to the surface with the help of flagella, and then penetrate into erythrocytes and endothelial cells of vessels and the endocardium, and subsequently stimulate the proliferation of endothelial cells and the growth of small vessels (capillaries), which can lead to the development of angiomatosis.

Usually, in cat scratch disease, the site of the entry gate determines the localization and form of the process (typical forms are those manifested by primary affect and regional lymphadenitis, atypical forms are ocular, CNS or other organ damage). Bacillary angiomatosis can be distinguished as a separate generalized form, characteristic of patients with HIV infection and other types of immunodeficiency.

At the sites of attachment of the pathogen to sensitive cells, clusters of microorganisms are formed with the development of inflammation and proliferation of endothelial cells and adjacent tissues. Some endothelial cells become necrotic. As a result, lymphadenopathy (mainly in typical forms of cat scratch disease), angiomatosis, or a combination of both with simultaneous damage to bone marrow cells and erythrocytes develop. Neutrophils and eosinophils are grouped around areas with "swollen" ("epithelioid") cells. Bacteria are found in erythrocytes, vascular endothelial cells, the spleen, lymph nodes, liver, bone marrow, and skin. In the heart valves of patients with severe endocarditis, numerous vegetations consisting of fibrin and platelets appear (microscopically, masses of extracellularly located pathogens and superficial inflammatory infiltrates on the valve flaps - perforations are determined. In individuals with immune deficiency, during the formation of chronic bacteremia, part of the B. henselae population in inflammatory infiltrates is localized intracellularly. In bacillary angiomatosis, the morphological basis of the disease is local proliferation of swollen endothelial cells protruding into the lumen of the vessels, therefore, with predominant damage to the skin, single or multiple (possibly more than 1000) painless papules and hemangiomas (often with the formation of a stalk) are found in various areas, rising above the skin level and sometimes reaching the size of lymph nodes. With a deeper subcutaneous location of vascular growths, nodular plexuses up to several centimeters in size. Necrosis is often possible, with minor damage - bleeding. Microscopy of biopsies stained with silvering reveals perivascular eosinophilic aggregates with areas of massive bacterial accumulations. A similar picture is observed with damage to internal organs; bone tissue necrosis may develop.

What are the symptoms of cat scratch disease?

Cat scratch disease has an incubation period that lasts from 3 to 20 (usually 7-14) days. A distinction is made between typical, ocular forms of the disease and bacillary angiomatosis. Typical forms are characterized by the development of primary affect and regional lymphadenitis. At the site of an already healed wound after a bite or scratch, a small painful papule from 2 to 5 mm in diameter with a rim of skin hyperemia appears, then it turns into a vesicle or pustule, and later - into a small ulcer (not always), covered with a dry crust. Papules occur in 60% of patients, but by the time a doctor is consulted, the inflammatory reaction disappears, the crust may fall off, the scratch heals, so the primary affect is often not detected. Primary affect is localized more often on the hand or forearm, less often on the face, neck, in the collarbone area, on the shin. The general condition is not disturbed. In half of the patients, after 1 month or more, suppuration of the lymph nodes occurs, they fuse with the skin; congestive hyperemia, fluctuation appear; a fistula is formed, from which pus is released within 2-3 months, then healing occurs with the formation of a scar. Regional lymphadenitis develops 15-30 days after infection - constant and sometimes the only symptoms of cat scratch disease. Most often, the axillary, elbow, less often - parotid and inguinal lymph nodes are affected. They reach a diameter of 3-5 cm or more, are usually dense, slightly painful, mobile; are not fused with each other, with the skin and surrounding tissues. The enlargement of the lymph nodes persists from 2-4 months to a year. From one to several (10-20% of cases) lymph nodes of the same group are involved in the process. Bilateral lymphadenopathy is rare. In this case, the lymph nodes reach a diameter of 2-3 cm. They are dense, painless, and do not suppurate. Symptoms of cat scratch disease: intoxication, fever, chills, weakness, headache, etc. are observed in 30-40% of patients. Body temperature can rise to 38-41 °C, be paroxysmal, and persist for 1 to 3 weeks. Weakness, increased fatigue, and headache are characteristic. The liver and spleen often enlarge, even in the absence of a febrile reaction. Cat scratch disease proceeds in waves. Damage to the nervous system is recorded in 5-6% of patients. It develops in severe cases of the disease 1-6 weeks after the onset of lymphadenopathy, is accompanied by severe fever, intoxication and can manifest as serous meningitis with low lymphocytic pleocytosis of the cerebrospinal fluid, radiculitis, polyneuritis, myelitis with paraplegia. Complications in severe cases of the disease include thrombocytopenic purpura, pneumonia, myocarditis, and splenic abscess.

If the conjunctiva serves as the entry point, an ocular form of the disease develops (3-7% of patients), resembling Parinaud's conjunctivitis. As a rule, one eye is affected. Against the background of fever and intoxication, pronounced edema of the eyelids and conjunctiva appears, chemosis develops. Gray-yellow nodules appear on the conjunctiva of the eyelids (or only the upper eyelid) and the transitional fold, which often ulcerate. The discharge from the conjunctival cavity is mucopurulent. The cornea is usually not affected. The lymph node located in front of the earlobe significantly increases in size and subsequently often suppurates with the formation of fistulas, after which cicatricial changes remain. Sometimes the submandibular lymph nodes also increase in size. Inflammatory changes persist for 1-2 weeks; the total duration of the disease ranges from 1 to 28 weeks.

In most patients, cat scratch disease occurs in the typical form described above. Sometimes the course of the disease is unusual and is accompanied by systemic damage to the body, which is manifested by the polymorphism of the clinical picture. Various rashes, thrombocytopenic purpura, damage to bones, joints, liver, spleen, and the development of visceral lymphadenopathy are possible. This course is mainly characteristic of people with severe immune damage and is well described in patients with HIV infection. These symptoms of cat scratch disease are often distinguished under the name "bacillary angiomatosis", which can be characterized as a generalized form of benign lymphoreticulosis. In this case, angiomatosis of the skin develops in the form of single or multiple painless papules of red or purple color, from point to larger, randomly located on various parts of the body, limbs, head and face. Later, the papules increase in size (to the size of lymph nodes or small tumors, resembling hemangiomas) and can rise above the skin like mushrooms. Some of them become purulent and resemble pyogenic granulomas. Sometimes lesions develop in the form of plaques with a hyperkeratosis or necrosis center. Many vascular growths bleed. With a deeper subcutaneous location of vascular growths, nodular formations appear, the size of which can reach several centimeters. They are also located on any part of the body, often diffusely throughout the body or head. A combination of superficial and deeper subcutaneous vascular growths is possible, as well as damage to the vessels of internal organs and bones, up to pronounced osteolysis. Bacillary angiomatosis occurs with fever, pronounced intoxication. A significant increase in ESR and leukocytosis are characteristic.

Some authors distinguish bacillary purple hepatitis (bacillary peliosis hepatitis) as an independent form of the disease, however, it is more correct to regard this form as a variant of the course of bacillary angiomatosis, in which signs of damage to the liver parenchyma predominate. Due to damage to small vessels of the liver, cystic formations filled with blood are formed in them, which compress the liver cells. As a result, blood stagnation develops and liver function is impaired. Complaints include nausea, diarrhea, bloating against the background of fever and chills. Examination reveals hepatosplenomegaly, anemia, thrombocytopenia, increased activity of liver enzymes in the blood serum, and histologically in liver biopsies - multiple dilated capillaries and cavernous spaces in the parenchyma filled with blood.

How is cat scratch disease diagnosed?

Diagnosis of cat scratch disease is based on the symptoms of the disease: a history of primary affect that arose after contact with a cat several days or weeks before the onset of the disease, enlargement of the regional lymph node.

The diagnosis can be confirmed by the results of a bacteriological blood test, as well as histologically: the papule or lymph node tissue is examined, staining them with silver according to Warthing-Starry in order to determine the accumulation of bacteria. In bacillary angiomatosis, nested accumulations of the pathogen are found in massive perivascular eosinophilic infiltrates. Electron microscopy clearly shows pleomorphic rods with a three-layer gram-negative membrane. Serodiagnostics are used: it makes it possible to detect antibodies in the blood (and an increase in their titer) to a specific antigen of the microorganism (RIF and ELISA). Molecular genetic methods using PCR have been developed.

Differential diagnosis of cat scratch disease

Differential diagnostics of cat scratch disease is carried out with tuberculosis of the lymph nodes, tularemia, bacterial lymphadenitis and other diseases. In all cases, it is necessary to take into account the characteristic anamnesis. In case of bacillary angiomatosis or severe systemic lesions, differential diagnostics of cat scratch disease is also carried out with Kaposi's sarcoma (mandatory histological examination).

Differential diagnosis of cat scratch disease

Sign	Cat scratch disease	Tuberculosis of the lymph nodes	Cutaneous bubonic tularemia	Bacterial lymphadenitis
Lymph nodes	Regional lymphadenitis, pain, edema, hyperemia of the skin, the process is unilateral	The lymph nodes of the cervical group are most often enlarged. Fistula formation is possible.	Regional lymphadenitis	Sharp pain, hyperemia of the skin, fluctuation, lymphangitis
Primary affect	Papule or scratch a few days before lymphadenitis	Absent	Painless ulcer with scarring	Absent
Rash	With the development of bacillary angiomatosis, single or multiple painless papules of red or purple color from pinpoint to very large, which subsequently increase in size. Nodular elements and bleeding are possible.	Absent	At the height of the disease, an allergic rash may occur (erythema, petechiae, vesicles; followed by pityriasis-like or lamellar peeling	Absent
Fever, intoxication	Possible with suppuration of the lymph node	None	Expressed from the 1st day of illness	Possible with suppuration of the lymph node

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Indications for consultation with other specialists

In the development of bacillary angiomatosis, a consultation with a dermatovenerologist is indicated for differential diagnostics with Kaposi's sarcoma and other skin lesions; in the case of suppuration of a lymph node, a consultation with a surgeon; in the case of the ocular form of the disease, an ophthalmologist's consultation. In the development of endocarditis in some patients, even against the background of long-term (4-6 months) intravenous administration of antibiotics, valve replacement may be necessary.

Indications for hospitalization

Indications for hospitalization are the need for differential diagnosis with lymphadenopathies of other etiologies, bacillary angiomatosis.

How is cat scratch disease treated?

Regime and diet

Home mode.

There is no need for a special diet.

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Drug treatment for cat scratch disease

In typical cases, symptomatic treatment of cat scratch disease is carried out; in case of suppuration of the lymph node, its puncture is performed with removal of pus. It is not recommended to open the lymph node, since fistulas may form, which do not heal for up to a year or more. In clinical practice, in particular, in case of suppuration of the lymph nodes, bacillary angiomatosis, ciprofloxacin is used at 0.5-1.0 g twice a day, azithromycin 0.5 g once a day, rifampicin 0.9 g / day in two doses. The duration of antibiotic therapy is 2-3 weeks. Doxycycline, tetracycline, roxithromycin, norfloxacin are also used. In case of bone damage, the combined use of fluoroquinolones and rifampicin is recommended. In addition to antibiotics, patients with HIV infection are prescribed antiretroviral treatment for cat scratch disease (as indicated).

Approximate periods of incapacity for work

The duration of disability depends on clinical recovery.

Clinical examination

Only patients with HIV infection undergo medical examination.

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How to prevent cat scratch disease?

Cat scratch disease has no specific prevention. Declawing is recommended, especially for kittens, and cat disinfestation. When caring for cats, it is necessary to observe personal hygiene rules. Cats should not be allowed outside. Bite wounds and scratches are treated with iodine or brilliant green tincture.