Endemic (Flea-Borne) Typhus Update
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- Flea-borne typhus is endemic in Orange County and cases may occur at any time. Incidence generally increases in the upcoming summer months in our area.
- Clinicians should consider typhus in patients with compatible symptoms and send testing.
- Typhus can be fatal. If typhus is suspected, empiric treatment should be considered pending test results.
- Report any suspect or confirmed cases of typhus to Epidemiology (phone 714-834-8180; fax 714-564-4050).
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Transmission
- Endemic (murine) typhus is caused by Rickettsia typhi or R. felis bacteria. Humans generally become infected through contact with infected fleas, most commonly when the infected flea feces is rubbed into a break in skin through scratching. Infected persons may not recall a flea bite. The incubation period is 6-14 days from exposure to onset of symptoms.
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Presentation
- Clinical manifestations are non-specific:
- Fever, chills, headache (can be severe), myalgias, malaise are common.
- Rash – macular or maculopapular, typically starts several days (4-7) after initial symptoms.
- Nausea, vomiting, abdominal pain, and cough may be present, along with hepatitis or pneumonia.
- Thrombocytopenia, leukopenia (neutropenia), transaminitis (increased AST and ALT) are often found on laboratory testing.
- Outcome:
- Most illnesses are self-limited and cases often recover by the time laboratory test results are available, rendering treatment at that time unnecessary (if recovered).
- Some cases are severe, with aseptic meningitis, encephalitis, renal failure, respiratory failure as uncommon complications in untreated cases.
- Death from typhus is rare (<2-4% of untreated cases worldwide).
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Diagnosis
- Serology:
- Send serum for R. typhi IgM and IgG and R. rickettsii IgM and IgG. Depending on the laboratory, these may also be ordered as Typhus IgM and IgG, and RMSF IgM and IgG, respectively.
- There is no specific serology available for R. felis.
- Rickettsial antibodies cross-react, so serology may be positive for R. typhi, R. rickettsii (the agent of Rocky Mountain Spotted Fever (RMSF)], or other ricksettsial species.
- Epidemiology may be able to assist with result interpretation based on the clinical presentation, exposure history, and laboratory results, if cross-reactivity among different rickettsial tests is reported.
- Antibody titers may be negative in the first week of illness, so repeat (convalescent) testing in patients with compatible symptoms may be needed.
- A four-fold rise in R. typhi IgG titers in paired acute and convalescent sera is diagnostic; a positive R. typhi IgM concurrent with a positive R. typhi IgG would also be considered a confirmed infection. A positive R. typhi IgM in the absence of a positive IgG would warrant convalescent testing as false positive R. typhi IgM are not uncommon.
- Additional testing: Polymerase chain reaction (PCR) detection of Rickettsia species nucleic acid is not readily available but may be arranged through Orange County Public Health if indicated on whole blood (5-10 cc in an EDTA purple top tube) taken during the acute illness.
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Treatment
- Doxycycline is the treatment of choice.
- If endemic typhus is strongly suspected, empiric treatment should be considered pending laboratory confirmation as testing turnaround may take several days and early treatment can prevent severe and fatal infections.
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Prevention
- There is no vaccine to prevent typhus.
- Prevention centers around avoiding contact with fleas:
- Discourage opossums, stray cats, rodents, or other animals in the yard:
- Eliminate outside food sources.
- Remove vegetation, brush and debris in the yard.
- Cover garbage containers.
- Consult your veterinarian about flea control products for pets.
- Keep cats indoors.
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Resources
Communicable disease reporting, local human case updates and questions:
Flea-borne typhus control and prevention:
Orange County Mosquito and Vector Control District 714-971-2421,
www.ocvector.org
Animal Health:
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