Louse- and flea-borne diseases

Louse- and flea-borne diseases are caused by pathogens that are transmitted by lice or fleas. The most dangerous flea-borne disease is plague as well as endemic typhus.

For more information on epidemic and endemic typhus, see “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)
• 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
• 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)
• 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
• 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
• Treatment
  • Doxycycline OR ceftriaxone
  • Children and pregnant woman: amoxicillin and cefuroxime

Borrelia recurentis causes a recurrent (relapsing) fever.

Plague

• Epidemiology: western US (as scattered cases in rural areas)
• Pathogen: Yersinia pestis
• Reservoir: : prairie dogs, squirrels, rodents
• Route of transmission: : flea bites
• Clinical features
  • Bubonic plague (most common):
    • Sudden onset of fever, headache, myalgias, chills, and painful swollen lymph nodes (buboes)
    • May progress to sepsis, pneumonia, and meningitis
  • Septicemic plague: signs and symptoms of sepsis, abdominal pain, possible shock, DIC
  • Pneumonic plague : rapidly progressing pneumonia with possible respiratory failure and shock
• Diagnostics
  • Culture
  • Microscopy with Wayson stain taken from buboes, blood, or sputum show bipolar staining of bacteria (appearance of “closed safety pin”)
• Treatment: Do not delay treatment for diagnosis. ^[1]
  • Isolation with droplet precautions until pneumonic plague is ruled out
  • First-line: IV gentamicin OR fluoroquinolones for 10–14 days
  • Second-line: doxycycline OR tetracycline