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Infectious Disease – Cat Scratch Disease
CAT-SCRATCH DISEASE (AND BARTONELLA INFECTIONS)
Cat-scratch disease is generally a self-limiting acute condition characterized by regional lymphadenopathy, fever, and systemic symptoms, resulting from Bartonella henselae infection. Other manifestations of B. henselae infection encompass fever of unknown origin, hepatosplenic granulomatous disease, neuroretinitis, and encephalopathy.
Other medically significant Bartonella species comprise: – Bartonella quintana, historically responsible for trench fever, linked with persistent bacteremia, endocarditis, and bacillary angiomatosis. – Bartonella bacilliformis, the etiological agent of Oroya fever.
Epidemiology
Occurrence
The prevalence of cat-scratch disease in the United States is roughly 10 cases per 100,000 person-years, with an estimated 24,000 cases identified annually.
Cat-scratch illness is prevalent globally. In temperate areas, it is seasonal, with the majority of cases occurring from August to January.
Cat-scratch illness manifests in immunocompetent individuals across all age groups, with 80% of cases occurring in those under 21 years old.
Most instances of cat-scratch sickness are self-resolving and linked to regional lymphadenopathy.
B. quintana is considered to be worldwide endemic.
B. bacilliformis infection is transmitted through sand fly bites and is exclusively found at altitudes exceeding 1 km in the Andes mountains.
FACTORS OF RISK
Cats serve as the primary hosts and reservoirs of B. henselae.
Most instances of cat-scratch disease can be directly associated with exposure to cats, particularly kittens or felines infested with fleas. Ninety percent of patients had a history of contact with cats.
- A prior history of cat scratch in 60% of cases.
• Incidences of B. quintana infection have been documented among homeless individuals and those from socioeconomically poor backgrounds. These circumstances render persons susceptible to Pediculus humanus (human body louse), a vector for B. quintana infection.
Patients with advanced HIV infection and other immunocompromised individuals are at elevated risk of
progressive chronic infections induced by B. quintana and B. henselae, encompassing bacillary angiomatosis (vascular lesions) and bacillary peliosis (cystic lesions).
COMPREHENSIVE PREVENTION
The risk of cat-scratch disease can be mitigated by minimizing interactions that could result in scratches, bites, or licks from cats or kittens.
The management of cat fleas may diminish the danger of transmission and may be beneficial in households with immunocompromised individuals.
PATHOPHYSIOLOGY • Bartonella species possess the ability for intracellular persistence and induce inflammation in affected organs.
The inflammatory response in cat-scratch disease leads to localized granuloma development.
ETIOLOGY • Bartonella species are meticulous gram-negative rod-shaped aerobic bacteria. • The predominant cause of cat-scratch disease is B. henselae.
• Additional medically significant Bartonella infections encompass
B. quintana and B. bacilliformis. Numerous additional Bartonella species have been linked to isolated instances of human illness.
FREQUENTLY CO-OCCURRING CONDITIONS
B. henselae and B. quintana induce a unique array of illnesses in HIV infection (see to the preceding section). Chronic infections may also arise in recipients of solid-organ transplants and individuals with hematological malignancies.
HISTORY OF DIAGNOSIS
The primary symptom of cat-scratch disease frequently manifests as a tiny erythematous papule or pustule at the scratch site, which endures for several weeks.
• Consequently, lymph nodes associated with the inoculation site become hypertrophied and sensitive.
Patients with cat-scratch disease may not consistently exhibit fever. Low-grade fever and malaise occur in 30% of patients.
Other indications of cat-scratch disease encompass prolonged fever, neuroretinitis (evidenced by diminished visual acuity or alterations in vision), and encephalopathy (characterized by abnormalities in mental status).
B. henselae bacteremia in individuals infected with HIV is linked to a gradual onset of lethargy, malaise, myalgia, weight loss, recurrent fevers of increasing duration and intensity, and occasionally, headaches. Hepatomegaly may be present.
Trench fever is the quintessential manifestation of B. quintana infection, and its natural progression in healthy individuals has been thoroughly documented. Incubation subsequent to inoculation
may extend from 3 to 38 days before to the typically abrupt emergence of chills and fevers. Afebrile infection represents the least prevalent variant. The accompanying symptoms and signs (e.g., headache, vertigo, retro-orbital pain, conjunctival infection) are all vague.
The physical morphology of bacillary angiomatosis is characterized by subcutaneous or dermal nodules and/or single or numerous dome-shaped papules that are skin-colored or red-to-purple, which may exhibit ulceration, serous or bloody exudate, and crusting. Visceral lesions can be notably striking, both in their quantity and the diversity of their macroscopic appearance.
Bacillary peliosis affects organs characterized by multiple blood-filled cystic formations, varying in size from microscopic to several millimeters.
PHYSICAL EXAM • Regional lymphadenopathy is the predominant physical manifestation in cat-scratch disease, occurring in lymph nodes that drain the inoculation site. • In numerous instances, a tiny granuloma or lesion may be identified at the site of inoculation.
Parinaud’s oculoglandular syndrome occurs in roughly 5% of individuals with cat-scratch disease, characterized by conjunctivitis, conjunctival granuloma, and preauricular lymphadenopathy.
Patients with visceral disease may exhibit hepatosplenomegaly.
DIAGNOSTIC EXAMINATIONS AND ANALYSIS
Laboratory Initial Assessments
In the initial stages of the disease, the total white blood cell count may reveal mild leukocytosis and an elevated count of polymorphonuclear cells, with eosinophilia observed in 10–20% of individuals.
B. henselae and B. quintana can be isolated from blood using lysis-centrifugation blood cultures; however, both species have also been successfully isolated with the BACTEC blood culture method.
Serological assays for B. henselae are being standardized. Numerous commercial testing laboratories do an indirect fluorescence assay. Low positive titers (1:64–1:256) may indicate recent or past infection, whereas titers beyond 1:256 strongly suggest active infection (2).
Subsequent Actions & Unique Considerations
In instances of inconclusive serology, a repeat test after two weeks may aid in confirming a diagnosis.
Imaging
Ultrasound of swollen lymph nodes can assist in assessing other causes of lymphadenopathy, identifying early suppuration of the bubo, and guiding needle aspiration as necessary.
Diagnostic Procedures and Additional Methods
Excisional biopsy or fine needle aspiration is frequently conducted in instances of regional lymphadenopathy.
Pathological Observations
Pathological findings reveal nonspecific granuloma development in the afflicted lymph nodes. A positive Warthin–Starry stain or tissue PCR for Bartonella indicates the possibility of cat-scratch disease, albeit they are not consistently positive.
DIFFERENTIAL DIAGNOSIS • The diagnosis of cat-scratch illness in individuals exhibiting regional lymphadenopathy or a clinical condition characteristic of cat-scratch disease is indicated by the following:
- Interaction with a feline and the existence of a scratch or
main lesion - A confirmed serological assay for Bartonella
– Distinct histopathologic features (the presence of many microabscesses or granulomas in a lymph node biopsy material)
– Exclusion of other recognizable etiologies, particularly mycobacterial infections and suppurative adenitis
INITIAL THERAPY MEDICATION
The literature contains numerous contradicting assertions regarding the role and selection of antibiotics for cat-scratch illness (3).
• While the condition typically resolves spontaneously, antibiotics may expedite recovery and are hence frequently employed in the treatment of cat-scratch disease.
Azithromycin (500 mg orally as a single dose, followed by 250 mg once day for the subsequent four days) is applicable for adults.
The management of cat-scratch neuroretinitis remains contentious; nonetheless, retrospective studies indicate that the combination of doxycycline and rifampin is linked to a more expedited alleviation of symptoms (4).
For bacillary angiomatosis limited to the skin, an oral regimen of erythromycin 500 mg administered four times daily or doxycycline 100 mg taken twice daily for a duration of 8–12 weeks is advised. Lesions typically start to diminish after a week, but generally require a somewhat longer duration to fully resolve and may result in residual hyperpigmentation.
If unresolved by 12 weeks, therapy should be prolonged.
• A minimum of 4 weeks of treatment is required for bacteremia.
Prolonged treatment (2–3 months) is warranted in an HIV-infected patient with chronic or recurrent fever, particularly in the context of endocarditis.
Second Line
Additional oral medications considered useful against cat-scratch disease include rifampin, ciprofloxacin, and trimethoprim-sulfamethoxazole.
OPERATIVE INTERVENTIONS/ADDITIONAL PROCEDURES
• In the event of suppuration, aspiration should be contemplated to alleviate pain and expedite recovery. Needle aspiration is typically favored over incision and drainage. Following the cleansing of the skin with an iodophor skin cleanser, aspiration can be performed by inserting an 18- or 19-gauge needle tangentially through healthy skin near the base of the node. Reaspiration may be required seldom.
In endocarditis, hemodynamic factors may necessitate valve replacement (see to chapters in Section II on endocarditis).
CONTINUING TREATMENT POST-CARE SUGGESTIONS
The lymphadenopathy associated with cat-scratch illness typically recovers spontaneously over several months.
• A single occurrence of cat-scratch sickness seems to provide enduring immunity. Occasionally, a reemergence of sinus tract drainage from the initially affected nodes may transpire. In cases of large adenopathy (>5 cm), chronic adenopathy may endure for 1 to 2 years.
• The resolution of fever in patients with bacteremia often occurs rapidly in non-HIV-infected individuals, however it may extend to several weeks in those infected with HIV. Typically, bacteremia becomes undetectable within a week of initiating medication, despite the potential continuation of fever.
DIET: Standard.
INFORMATION FOR PATIENTS
Patients must be informed about the transmission method and the possible dangers to immunocompromised others in the household who have comparable exposure to cats.
OUTLOOK
Simple cat-scratch illness has a favorable prognosis. Lymphadenopathy related to mild cat-scratch disease in immunocompetent persons heals within weeks to many months. Complications including retinitis, encephalopathy, or severe systemic disease manifest in 5–14% of instances.
COMPLICATIONS
• Encephalopathy typically manifests many weeks following the severe sickness. Seizures and status epilepticus may indicate encephalopathy but are self-limiting, with prompt recovery typically occurring within a few days. The cerebrospinal fluid is typically normal, although pleocytosis may arise. The etiology of the encephalopathy remains ambiguous, while direct infection, a toxin, and an autoimmune mechanism have been suggested as contributing factors.
Inflammatory responses to B. henselae infection in individuals with AIDS, absent of accompanying angiomatosis or peliosis, have been seen affecting the liver and spleen.
lymph nodes, cardiac organ, and bone marrow
CAT-SCRATCH DISEASE (AND BARTONELLA INFECTIONS)
Cat-scratch disease is generally a self-limiting acute condition characterized by regional lymphadenopathy, fever, and systemic symptoms, resulting from Bartonella henselae infection. Other manifestations of B. henselae infection encompass fever of unknown origin, hepatosplenic granulomatous disease, neuroretinitis, and encephalopathy.
Other medically significant Bartonella species comprise: – Bartonella quintana, historically responsible for trench fever, linked with persistent bacteremia, endocarditis, and bacillary angiomatosis. – Bartonella bacilliformis, the etiological agent of Oroya fever.
Epidemiology
Occurrence
The prevalence of cat-scratch disease in the United States is roughly 10 cases per 100,000 person-years, with an estimated 24,000 cases identified annually.
Cat-scratch illness is prevalent globally. In temperate areas, it is seasonal, with the majority of cases occurring from August to January.
Cat-scratch illness manifests in immunocompetent individuals across all age groups, with 80% of cases occurring in those under 21 years old.
Most instances of cat-scratch sickness are self-resolving and linked to regional lymphadenopathy.
B. quintana is considered to be worldwide endemic.
B. bacilliformis infection is transmitted through sand fly bites and is exclusively found at altitudes exceeding 1 km in the Andes mountains.
FACTORS OF RISK
Cats serve as the primary hosts and reservoirs of B. henselae.
Most instances of cat-scratch disease can be directly associated with exposure to cats, particularly kittens or felines infested with fleas. Ninety percent of patients had a history of contact with cats.
- A prior history of cat scratch in 60% of cases.
• Incidences of B. quintana infection have been documented among homeless individuals and those from socioeconomically poor backgrounds. These circumstances render persons susceptible to Pediculus humanus (human body louse), a vector for B. quintana infection.
Patients with advanced HIV infection and other immunocompromised individuals are at elevated risk of
progressive chronic infections induced by B. quintana and B. henselae, encompassing bacillary angiomatosis (vascular lesions) and bacillary peliosis (cystic lesions).
COMPREHENSIVE PREVENTION
The risk of cat-scratch disease can be mitigated by minimizing interactions that could result in scratches, bites, or licks from cats or kittens.
The management of cat fleas may diminish the danger of transmission and may be beneficial in households with immunocompromised individuals.
PATHOPHYSIOLOGY • Bartonella species possess the ability for intracellular persistence and induce inflammation in affected organs.
The inflammatory response in cat-scratch disease leads to localized granuloma development.
ETIOLOGY • Bartonella species are meticulous gram-negative rod-shaped aerobic bacteria. • The predominant cause of cat-scratch disease is B. henselae.
• Additional medically significant Bartonella infections encompass
B. quintana and B. bacilliformis. Numerous additional Bartonella species have been linked to isolated instances of human illness.
FREQUENTLY CO-OCCURRING CONDITIONS
B. henselae and B. quintana induce a unique array of illnesses in HIV infection (see to the preceding section). Chronic infections may also arise in recipients of solid-organ transplants and individuals with hematological malignancies.
HISTORY OF DIAGNOSIS
The primary symptom of cat-scratch disease frequently manifests as a tiny erythematous papule or pustule at the scratch site, which endures for several weeks.
• Consequently, lymph nodes associated with the inoculation site become hypertrophied and sensitive.
Patients with cat-scratch disease may not consistently exhibit fever. Low-grade fever and malaise occur in 30% of patients.
Other indications of cat-scratch disease encompass prolonged fever, neuroretinitis (evidenced by diminished visual acuity or alterations in vision), and encephalopathy (characterized by abnormalities in mental status).
B. henselae bacteremia in individuals infected with HIV is linked to a gradual onset of lethargy, malaise, myalgia, weight loss, recurrent fevers of increasing duration and intensity, and occasionally, headaches. Hepatomegaly may be present.
Trench fever is the quintessential manifestation of B. quintana infection, and its natural progression in healthy individuals has been thoroughly documented. Incubation subsequent to inoculation
may extend from 3 to 38 days before to the typically abrupt emergence of chills and fevers. Afebrile infection represents the least prevalent variant. The accompanying symptoms and signs (e.g., headache, vertigo, retro-orbital pain, conjunctival infection) are all vague.
The physical morphology of bacillary angiomatosis is characterized by subcutaneous or dermal nodules and/or single or numerous dome-shaped papules that are skin-colored or red-to-purple, which may exhibit ulceration, serous or bloody exudate, and crusting. Visceral lesions can be notably striking, both in their quantity and the diversity of their macroscopic appearance.
Bacillary peliosis affects organs characterized by multiple blood-filled cystic formations, varying in size from microscopic to several millimeters.
PHYSICAL EXAM • Regional lymphadenopathy is the predominant physical manifestation in cat-scratch disease, occurring in lymph nodes that drain the inoculation site. • In numerous instances, a tiny granuloma or lesion may be identified at the site of inoculation.
Parinaud’s oculoglandular syndrome occurs in roughly 5% of individuals with cat-scratch disease, characterized by conjunctivitis, conjunctival granuloma, and preauricular lymphadenopathy.
Patients with visceral disease may exhibit hepatosplenomegaly.
DIAGNOSTIC EXAMINATIONS AND ANALYSIS
Laboratory Initial Assessments
In the initial stages of the disease, the total white blood cell count may reveal mild leukocytosis and an elevated count of polymorphonuclear cells, with eosinophilia observed in 10–20% of individuals.
B. henselae and B. quintana can be isolated from blood using lysis-centrifugation blood cultures; however, both species have also been successfully isolated with the BACTEC blood culture method.
Serological assays for B. henselae are being standardized. Numerous commercial testing laboratories do an indirect fluorescence assay. Low positive titers (1:64–1:256) may indicate recent or past infection, whereas titers beyond 1:256 strongly suggest active infection (2).
Subsequent Actions & Unique Considerations
In instances of inconclusive serology, a repeat test after two weeks may aid in confirming a diagnosis.
Imaging
Ultrasound of swollen lymph nodes can assist in assessing other causes of lymphadenopathy, identifying early suppuration of the bubo, and guiding needle aspiration as necessary.
Diagnostic Procedures and Additional Methods
Excisional biopsy or fine needle aspiration is frequently conducted in instances of regional lymphadenopathy.
Pathological Observations
Pathological findings reveal nonspecific granuloma development in the afflicted lymph nodes. A positive Warthin–Starry stain or tissue PCR for Bartonella indicates the possibility of cat-scratch disease, albeit they are not consistently positive.
DIFFERENTIAL DIAGNOSIS • The diagnosis of cat-scratch illness in individuals exhibiting regional lymphadenopathy or a clinical condition characteristic of cat-scratch disease is indicated by the following:
- Interaction with a feline and the existence of a scratch or
main lesion - A confirmed serological assay for Bartonella
– Distinct histopathologic features (the presence of many microabscesses or granulomas in a lymph node biopsy material)
– Exclusion of other recognizable etiologies, particularly mycobacterial infections and suppurative adenitis
INITIAL THERAPY MEDICATION
The literature contains numerous contradicting assertions regarding the role and selection of antibiotics for cat-scratch illness (3).
• While the condition typically resolves spontaneously, antibiotics may expedite recovery and are hence frequently employed in the treatment of cat-scratch disease.
Azithromycin (500 mg orally as a single dose, followed by 250 mg once day for the subsequent four days) is applicable for adults.
The management of cat-scratch neuroretinitis remains contentious; nonetheless, retrospective studies indicate that the combination of doxycycline and rifampin is linked to a more expedited alleviation of symptoms (4).
For bacillary angiomatosis limited to the skin, an oral regimen of erythromycin 500 mg administered four times daily or doxycycline 100 mg taken twice daily for a duration of 8–12 weeks is advised. Lesions typically start to diminish after a week, but generally require a somewhat longer duration to fully resolve and may result in residual hyperpigmentation.
If unresolved by 12 weeks, therapy should be prolonged.
• A minimum of 4 weeks of treatment is required for bacteremia.
Prolonged treatment (2–3 months) is warranted in an HIV-infected patient with chronic or recurrent fever, particularly in the context of endocarditis.
Second Line
Additional oral medications considered useful against cat-scratch disease include rifampin, ciprofloxacin, and trimethoprim-sulfamethoxazole.
OPERATIVE INTERVENTIONS/ADDITIONAL PROCEDURES
• In the event of suppuration, aspiration should be contemplated to alleviate pain and expedite recovery. Needle aspiration is typically favored over incision and drainage. Following the cleansing of the skin with an iodophor skin cleanser, aspiration can be performed by inserting an 18- or 19-gauge needle tangentially through healthy skin near the base of the node. Reaspiration may be required seldom.
In endocarditis, hemodynamic factors may necessitate valve replacement (see to chapters in Section II on endocarditis).
CONTINUING TREATMENT POST-CARE SUGGESTIONS
The lymphadenopathy associated with cat-scratch illness typically recovers spontaneously over several months.
• A single occurrence of cat-scratch sickness seems to provide enduring immunity. Occasionally, a reemergence of sinus tract drainage from the initially affected nodes may transpire. In cases of large adenopathy (>5 cm), chronic adenopathy may endure for 1 to 2 years.
• The resolution of fever in patients with bacteremia often occurs rapidly in non-HIV-infected individuals, however it may extend to several weeks in those infected with HIV. Typically, bacteremia becomes undetectable within a week of initiating medication, despite the potential continuation of fever.
DIET: Standard.
INFORMATION FOR PATIENTS
Patients must be informed about the transmission method and the possible dangers to immunocompromised others in the household who have comparable exposure to cats.
OUTLOOK
Simple cat-scratch illness has a favorable prognosis. Lymphadenopathy related to mild cat-scratch disease in immunocompetent persons heals within weeks to many months. Complications including retinitis, encephalopathy, or severe systemic disease manifest in 5–14% of instances.
COMPLICATIONS
• Encephalopathy typically manifests many weeks following the severe sickness. Seizures and status epilepticus may indicate encephalopathy but are self-limiting, with prompt recovery typically occurring within a few days. The cerebrospinal fluid is typically normal, although pleocytosis may arise. The etiology of the encephalopathy remains ambiguous, while direct infection, a toxin, and an autoimmune mechanism have been suggested as contributing factors.
Inflammatory responses to B. henselae infection in individuals with AIDS, absent of accompanying angiomatosis or peliosis, have been seen affecting the liver and spleen.
lymph nodes, cardiac organ, and bone marrow
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