Murine typhus

Fleaborne infection caused by Rickettsia typhi and characterized by fever, rash, and body aches.

ARDS in murine typhus

Cause

• Flea-borne (murine) typhus, is a disease caused by a bacteria called Rickettsia typhi.
• Flea-borne typhus is spread to people through contact with infected fleas.

• ==Pathophysiology==
• Fleas become infected when they bite infected animals, such as rats, cats, or opossums. When an infected flea bites a person or animal, the bite breaks the skin, causing a wound. Fleas poop when they feed.
• The poop (also called flea dirt) can then be rubbed into the bite wound or other wounds causing infection.
• People can also breathe in infected flea dirt or rub it into their eyes.
• This bacteria is not spread from person to person.
• Flea-borne typhus occurs in tropical and subtropical climates around the world including areas of the United States (southern California, Hawaii, and Texas).
• Flea-borne typhus is a rare disease in the United States.

Signs and Symptoms

Symptoms of flea-borne typhus begin within 2 weeks after contact with infected fleas or flea dirt. Signs and symptoms may include:

• Fever and chills
• Body aches and muscle pain
• Loss of appetite
• Nausea
• Vomiting
• Stomach pain
• Cough
• Rash (typically occurs around day 5 of illness)

Severe illness is rare and most people recover completely, sometimes without treatment. Untreated disease can cause severe illness and damage to one or more organs, including the liver, kidneys, heart, lungs, and brain.

Diagnosis and Testing

• The symptoms of flea-borne typhus are similar to symptoms of many other diseases.
• Rickettsia typhi can be detected via indirect immunofluorescence antibody (IFA) assay, immunohistochemistry (IHC), polymerase chain reaction (PCR) assays using blood, plasma, or tissue samples, or culture isolation.
• PCR is most sensitive on samples taken during the first week of illness, but prior to the start of doxycycline.
• Serologic tests (typically using IFA) are the most common means of confirming murine typhus and can be used to detect either IgG or IgM antibodies.
• Diagnosis is usually confirmed by demonstrating a four-fold rise in antibody titer between acute and convalescent samples.
• Acute specimens are taken during the first week of illness and convalescent samples are taken 2–4 weeks later.
• IgG antibodies are considered more accurate than IgM. Detectable levels of IgG antibody generally do not appear until 7–10 days after the onset of illness.
• Because antibody titers may persist in some individuals for years after the original exposure, only demonstration of recent changes in titers between paired specimens can be considered reliable serological confirmation of an acute murine typhus infection.
• R. typhi antigens frequently cross-react with those of R. prowazekii and R. felis, and less often with R. rickettsii.
• When possible, species-specific assays for R. typhi, R. prowazekii, R. felis, and R. rickettsii should be run in parallel.
• IHC can be used to detect infection with typhus group Rickettsia (including R. prowazekii and R. typhi) in formalin-fixed tissue samples.
• PCR of whole blood or tissue can distinguish between infection with R. typhi and R. prowazekii although the sensitivity of these assays varies considerably based on the sample type, timing of sample collection, and the severity of disease.

Treatment

• Flea-borne typhus is treated with the antibiotic doxycycline. Doxycycline can be used in persons of any age.
• Antibiotics are most effective when given soon after symptoms begin.
• People treated early with doxycycline usually recover quickly.
• There is no evidence that persistent or chronic infections occur.

Prevention

• There is no vaccine to prevent flea-borne typhus.
• Reduce your risk of getting flea-borne typhus by avoiding contact with fleas.
• Keep fleas off of your pets. Use veterinarian-approved flea control products for cats and dogs such as flea collars, oral medication or spot-ons. Permethrin should not be used on cats. Animals that are allowed outside are more likely to come in contact with fleas and could bring them inside.
• Keep rodents and animals (e.g. opossums) away from your home, workplace, and recreational areas:
• Store food, including pet food, in tight sealing containers.
• Remove brush, rock piles, junk, and cluttered firewood outside of your home.
• Seal up holes in your home where rodents can enter.
• Keep tight lids on compost and trash cans.
• The CDC’s rodents website offers helpful suggestions on rodent control during and after a rodent infestation.
• Protect yourself from flea bites:
• Do not feed or pet stray or wild animals.
• Always wear gloves if you are handling sick or dead animals.
• Use EPA-registered insect repellents on your skin and clothing when spending time outside. Always follow instructions listed on the product label.

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