Summary
Louse- and flea-borne diseases are caused by pathogens that are transmitted by lice or fleas. The most dangerous flea-borne diseases are plague and murine typhus.
Louse-borne diseases
Epidemic typhus is a louse-borne disease that is described separately in “Typhus.”
Trench fever (five-day fever)
- Epidemiology: most commonly affects people who are at risk of body louse infestation (e.g., homeless)
- Etiology: Bartonella quintana
- Transmission: : feces of infected body louse (vector)
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Clinical features
- Recurrent fever episodes that last ∼ 5 days
- Nonspecific, flu-like symptoms (malaise, headache, nausea, vomiting)
- Bone pain, splenomegaly, and maculopapular rash of the trunk may occur
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Diagnostics: isolation of Bartonella confirms the diagnosis
- Bartonella is difficult to grow on culture
- Serology testing or PCR are often necessary
- Treatment: doxycycline PLUS gentamicin
Louse-borne relapsing fever
- Epidemiology: most common in areas affected by overcrowding, war, refugee camps
- Pathogen: Borrelia recurrentis
- Transmission: : feces of infected body louse (vector)
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Clinical features
- Recurring episodes of high fever (39–43°C) lasting 3–6 days followed by an afebrile period of 7 days
- Other symptoms include headache, arthralgia, nausea, confusion, macular rash
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Diagnostics
- Confirmatory test: detection of B. recurrentis in peripheral blood smear, bone marrow, or CSF with Wright or Giemsa stain
- Culture is difficult
- Laboratory studies: normocytic anemia, thrombocytopenia , ↑ ESR
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Treatment
- Doxycycline OR ceftriaxone
- Children and pregnant woman: amoxicillin and cefuroxime
Flea-borne diseases
Murine typhus is a flea-borne disease that is described separately in “Typhus.”
Plague
Epidemiology [1]
- Endemic in western US (as scattered cases in rural areas)
- Certain foci in Asia (e.g., India), South America, and sub-Saharan Africa (e.g., Madagascar)
Etiology [1][2]
- Pathogen: Yersinia pestis
- Reservoir: : prairie dogs, squirrels, rodents
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Transmission
- Bites by infected fleas (most common)
- Rarely: contact with tissue or respiratory droplets from an infected animal or human [2]
Y. pestis is highly infectious and is considered a pathogen of the highest concern as a possible bioweapon. [2]
Clinical features [1][2]
The signs and symptoms of plague depend on the clinical form of the disease.
- Incubation period: 1–8 days [1][2]
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Bubonic plague (most common)
- Sudden onset of fever, headache, myalgias, chills, and painful swollen lymph nodes (buboes)
- May progress to sepsis, pneumonia, and meningitis.
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Pneumonic plague
- Signs of pneumonia, e.g., fever, dyspnea, productive cough [2]
- Rapid progression with possible respiratory failure and shock if untreated
- Septicemic plague: clinical features of sepsis, possible shock, gastrointestinal symptoms (e.g., abdominal pain, diarrhea), acral gangrene, without localizing signs [1][2]
- Rare forms: meningeal , pharyngeal [2]
Diagnostics [1][3]
Suspect plague in patients with concerning clinical features who report recent travel to endemic areas or contact with rodents or other vectors. Detection of Y. pestis on microscopy or culture, or serologic detection of F1 antigen confirms the diagnosis.
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Microbiology
- Bacterial cultures from blood, sputum, CSF, or bubo aspirate depending on the presentation
- Direct visualization and staining on microscopy
- Wayson stain: bipolar staining of bacteria (appearance of “closed safety pin”)
- Gram stain: small gram-negative coccobacilli
- Serology: detects antibodies to F1 antigen of Y. pestis [3]
- Rapid tests: detects F1 antigen; highly sensitive and can be used to support diagnosis in remote areas [4][5]
Plague is a nationally notifiable disease. [1]
Treatment [2]
Immediately start antibiotic therapy for 10–14 days. [2]
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Bubonic or pharyngeal plague
- First-line: fluoroquinolones, e.g., ciprofloxacin , doxycycline , or aminoglycosides, e.g., gentamicin (off-label) [2]
- Second-line: chloramphenicol (off-label) [2]
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Pneumonic or septicemic plague
- First-line: fluoroquinolones, e.g., ciprofloxacin , or aminoglycosides, e.g., gentamicin (off-label) [2]
- Second-line: tetracyclines, e.g., doxycycline [2]
- Plague meningitis: chloramphenicol (off-label) or fluoroquinolones, e.g., levofloxacin [2]
Do not delay treatment for diagnostics. [3]
Prevention [1][2]
- Infection control: Implement droplet precautions for patients with pneumonic plague.
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Post-exposure prophylaxis: Consider for individuals who have had direct contact with a person with pneumonic plague, an infected animal, or infectious materials.
- Doxycycline [2]
- OR a fluoroquinolone, e.g., ciprofloxacin [2]
- Vaccination is not currently available in the US.