scrub typhus

What is Scrub Typhus?

Scrub typhus, also known as bush typhus, is a severe infectious disease caused by the rickettsial bacterium Orientia tsutsugamushi [3][10]. It is transmitted to humans through bites from infected larval trombiculid mites, commonly known as chiggers [1].

Geographical Distribution

Scrub typhus is endemic in an area of Asia-Pacific bounded by Japan, Korea, China, India, and northern Australia [2]. The disease is a serious public health concern in this region, affecting over 1 billion people across 8 million square kilometers [3].

Symptoms and Signs

The symptoms of scrub typhus start suddenly after an incubation period of 6 to 21 days (mean 10 to 12 days) [4]. They include:

• Fever
• Chills
• Headache
• Generalized lymphadenopathy
• A sore on the skin with a "punched out" appearance (skin ulcer that becomes dark in the center) at the site where the mite attached [6]

Clinical Picture

The clinical picture of scrub typhus is characterized by sudden onset fever with chills and non-specific symptoms such as headache, myalgia, sweating, and vomiting [7].

Outcome after Scrub Typhus

With appropriate and timely treatment, scrub typhus symptoms should start to improve within 48 hours, and the patient should be completely recovered in 7–10 days [13]. However, if left untreated, the mortality associated with scrub typhus may be as high as 60% [13].

Treatment and Diagnosis

Scrub typhus is treated with an antibiotic. The bacteria that cause scrub typhus can live only inside the cells of other organisms, making diagnosis challenging. Doctors test a sample of the rash and sometimes do blood tests to diagnose the infection [15].

Common Signs and Symptoms of Scrub Typhus

Scrub typhus, also known as bush typhus, is a bacterial infection caused by the Orientia tsutsugamushi bacterium. The symptoms of scrub typhus can vary in severity, but they typically begin within 6 to 21 days after the bite of an infected chigger.

Common Symptoms:

• Fever and Chills: A sudden onset of fever and chills is a common symptom of scrub typhus.
• Headache: Headaches are another frequent symptom, which can range from mild to severe.
• Body Aches and Muscle Pain: Many people experience body aches and muscle pain as the infection takes hold.
• Eschar: A dark, scab-like region (eschar) often develops at the site of the chigger bite.
• Mental Changes: In some cases, scrub typhus can cause mental changes, ranging from confusion to coma.

Other Possible Symptoms:

• Swollen lymph nodes
• Cough during the first week of fever
• Rash (appears about 5 to 8 days after the fever starts)

It's essential to seek medical attention if you suspect you have scrub typhus. Early treatment can help alleviate symptoms and prevent complications.

References:

[1] Signs and symptoms. Symptoms of scrub typhus usually begin within 10 days after infection. (Source: #1) [2] Typical signs and symptoms include: Fever and chills; Headache; Myalgia; Eschar; Altered mental status, ranging from confusion to coma or delirium; (Source: #2) [3] After an incubation period of 6 to 21 days (mean 10 to 12 days), symptoms of scrub typhus start suddenly and include fever, chills, headache, and generalized lymphadenopathy. (Source: #3) [4] The typical lesion of scrub typhus begins as a red ... (Source: #13)

Diagnostic Tests for Scrub Typhus

Scrub typhus, caused by the bacterium Orientia tsutsugamushi, is a disease that requires prompt diagnosis and treatment to prevent life-threatening complications. Several diagnostic tests are available to confirm the presence of scrub typhus in patients.

• Serological Tests: These tests detect antibodies against Orientia tsutsugamushi in the patient's blood or serum. The Weil-Felix test, indirect Immunofluorescence assays (IFA), and enzyme-linked immunosorbent assay (ELISA) are commonly used serological tests for scrub typhus diagnosis [3][4][10].
  • Weil-Felix Test: Although the oldest test still in use today, it lacks sensitivity and specificity for scrub typhus diagnosis. It relies on cross-reactivity of the Proteus OXK strain for serodiagnosis [10].
• Immunoperoxidase Test: This is a confirmatory test that detects antibodies against Orientia tsutsugamushi in patient's serum or blood [4].
• PCR (Polymerase Chain Reaction): PCR is a molecular diagnostic technique that can detect the genetic material of Orientia tsutsugamushi. It is considered a direct method of diagnosis and is more reliable than serological tests [14].
• Rapid Diagnostic Tests (RDTs): RDTs

Treatment Options for Scrub Typhus

Scrub typhus, a bacterial infection caused by Orientia tsutsugamushi, requires prompt and effective treatment to prevent complications and ensure recovery. The primary goal of treatment is to eliminate the bacteria from the body.

• Doxycycline: This antibiotic is considered the first-line treatment for scrub typhus in individuals of all ages [9][10]. It is essential to treat patients with doxycycline for at least 3 days after the fever subsides and until there is evidence of clinical improvement. Single-dose or short courses may lead to a relapse in illness.
• Azithromycin: Combination therapy with intravenous doxycycline and azithromycin has been shown to be more effective than monotherapy for treating severe scrub typhus [2][8].
• Chloramphenicol: This antibiotic is also used to treat scrub typhus, although its use may be limited due to potential side effects.
• Tetracycline derivatives: These are the mainstays of scrub typhus treatment and include doxycycline and tetracycline [5][6].

Key Considerations

• Early access to effective drug therapy is crucial in reducing disease damage and preventing complications.
• The appropriate antibiotic treatment for severe scrub typhus is unclear, and further research is needed to establish the most effective regimens and outcome measures.

References:

[2] Varghese GM, Dayanand D, Gunasekaran K, et al. Intravenous Doxycycline, Azithromycin, or Both for Severe Scrub Typhus. [5] Sep 29, 2023 — Tetracycline derivatives (eg, doxycycline) are the mainstays of scrub typhus treatment. [6] by J Yang · 2020 · Cited by 25 — So far, doxycycline, azithromycin, and chloramphenicol are common antibiotics for treating scrub typhus. [8] Mar 1, 2023 — “Combination therapy with intravenous doxycycline and azithromycin is a better, more effective way to treat severe scrub typhus than monotherapy.” [9] Treatment. Doxycycline is the treatment of choice for suspected scrub typhus in persons of all ages. [10] The current treatment for scrub typhus is administration of a tetracycline (most commonly doxycycline).

Differential Diagnosis of Scrub Typhus

Scrub typhus, caused by the bacterium Orientia tsutsugamushi, is a mite-borne, acute febrile illness that can range from mild and self-limited to severe or fatal. When considering differential diagnoses for scrub typhus, several infectious diseases should be taken into account.

Other Rickettsial Diseases

• Spotted Fevers: These include diseases such as Rocky Mountain spotted fever and Mediterranean spotted fever, which are also caused by rickettsiae.
• Murine Typhus: This is another disease caused by the bacterium Rickettsia typhi, which can present with similar symptoms to scrub typhus.

Other Acute Febrile Illnesses

• Typhoid Fever: Caused by Salmonella Typhi, this disease can also present with fever, headache, and abdominal pain.
• Leptospirosis: This bacterial infection can cause a range of symptoms including fever, headache, and muscle aches.
• Malaria: A mosquito-borne illness that can cause fever, chills, and flu-like symptoms.
• Dengue Fever: Another mosquito-borne disease that can present with high fever, headache, and rash.

Other Considerations

• HIV Seroconversion: In patients with HIV/AIDS, a new or worsening febrile illness should raise suspicion of HIV seroconversion.
• Rickettsial Diseases: Other rickettsial diseases such as typhus and spotted fever should also be considered in the differential diagnosis.

Key Points

• Scrub typhus is a mite-borne, acute febrile illness caused by Orientia tsutsugamushi.
• Differential diagnoses for scrub typhus include other rickettsial diseases, typhoid fever, leptospirosis, malaria, dengue fever, and HIV seroconversion.
• Early diagnosis and prompt institution of doxycycline therapy may lead to early cure of scrub typhus even when features of meningitis supervene.

References

[1] Scrub typhus is a mite-borne, acute febrile illness caused by the bacterium Orientia tsutsugamushi. It is a re-emerging infectious disease of the tsutsugamushi triangle. Scrub typhus is transmitted through bites of contaminated chiggers (larval stage). Diagnosis of scrub typhus is challenging as its symptoms mimic with other acute febrile illnesses [11].

[2] Several differential diagnoses are considered to present when a patient exhibits acute febrile sickness. One significant cause is included in the differential diagnosis: scrub typhus [13].

[3] Scrub typhus is an important differential diagnosis in patients who present with acute undifferentiated fever in South East Asia [4].