Scrub Typhus: Causes, Sign & Symptoms, Preventions & Treatment

Scrub typhus


What is Typhus?

Typhus is a disease caused by an infection with the Rickettsia bacteria. Fleas, mites (chiggers), lice, or ticks transmit it when they bite you. Fleas, mites, lice, and ticks are types of invertebrate animals known as arthropods. When infected arthropods bite someone, they may leave the bacteria that cause typhus behind. Scratching the bite opens the skin and allows the bacteria to enter the bloodstream. Once in the bloodstream, the bacteria reproduce and grow.

There are three different types of typhus:

  • epidemic (or louse-borne) typhus
  • endemic typhus
  • scrub typhus

The type of typhus you are infected with depends on what bit you. Arthropods are typically carriers of one typhus strain unique to their species.

Typhus outbreaks usually only occur in developing countries or in regions of poverty, poor sanitation, and close human contact. Typhus is generally not a problem in the United States, but you may become infected while traveling abroad.

Untreated typhus can lead to serious complications and it’s potentially fatal. It’s important to see your doctor if you suspect that you may have typhus.

Scrub typhus Signs and Symptoms

Elements brought out in the history may include the following:

  • Travel to an area where scrub typhus is endemic
  • Chigger bite (often painless and unnoticed)
  • Incubation period of 6-20 days (average, 10 days)
  • Headaches, shaking chills, lymphadenopathy, conjunctival injection, fever, anorexia, and general apathy
  • Rash; a small, painless, gradually enlarging papule, which leads to an area of central necrosis and is followed by eschar formation

Although many other conditions can present with a high fever, the presentation of the rash, a history of exposure to endemic areas, and the presentation of the sore caused by the bite can be diagnostic of scrub fever.

Physical findings may include the following:

  • Site of infection marked by a chigger bite
  • Eschar at the inoculation site (in about 50% of patients with primary infection and 30% of those with recurrent infection)
  • High fever (40-40.5°C [104-105°F]), occurring more than 98% of the time
  • Tender regional or generalized lymphadenopathy, occurring in 40-97% of cases
  • Less frequently, ocular pain, wet cough, malaise, and injected conjunctiva
  • Centrifugal macular rash on the trunk
  • Enlargement of the spleen, cough, and delirium
  • Pneumonitis or encephalitis
  • Central nervous system (CNS), pulmonary, or cardiac involvement
  • Rarely, acute renal failure, shock, and disseminated intravascular coagulation (DIC)

Scrub typhus Causes

Scrub typhus is caused by a bacterium called Orientia tsutsugamushi. It has the ability to survive inside the cells of our body. It is transmitted to humans by the larva of a mite, called a “chigger”. These mites maintain infection among themselves by passing the bacteria onto their offspring, but only the “larval stage” of the mite (one of four life cycle stages: egg, larva, nymph and adult) can transmit the bacterium to human beings.

Scrub literally means a specific type of vegetation, somewhat similar to woods, and it is where the mite is most often found. But it can also be seen in semiarid areas and deserts. Mites can also spread rickettsial pox.

Scrub typhus Prevention

During World War II, a vaccine was created to prevent epidemic typhus. However, the shrinking number of cases has stopped the manufacture of the vaccine. The easiest way to prevent typhus is by avoiding the insects that spread it.

Suggestions for prevention include:

  • maintaining personal hygiene (helps guard against lice carrying the disease)
  • controlling the rodent population (rodents are known to carry arthropods)
  • avoiding travel to regions where typhus exposure has occurred, or to countries that are high risk due to lack of sanitation
  • chemoprophylaxis with doxycycline (used as a preventive only in those at high risk, such as those on humanitarian campaigns in areas with extreme poverty and little or no sanitation)

Use tick and insect repellant. Perform routine examinations for ticks, and wear protective clothing if you’re traveling near an area where there have been typhus outbreaks.

Scrub typhus Treatment

Scrub typhus is treated with antibiotics. Chloramphenicol (Chloromycetin, Fenicol) and tetracycline (Achromycin, Tetracyn) are the drugs of choice. They bring about prompt disappearance of the fever and dramatic clinical improvement. If the antibiotic treatment is discontinued too quickly, especially in patients treated within the first few days of the fever, relapses may occur. In patients treated in the second week of illness, the antibiotics may be stopped one to two days after the fever disappears.

Antibiotics are given intravenously to patients too sick to take them by mouth. Patients who are severely ill and whose treatment was delayed may be given corticosteroids in combination with antibiotics for three days.

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