Scrub Typhus in Children
On this page
Direct answer
Scrub typhus is a rickettsial infection caused by Orientia tsutsugamushi and transmitted by the bite of infected larval trombiculid mites, called chiggers. It presents with fever, headache and a characteristic painless black eschar at the bite site, often with lymphadenopathy. Doxycycline is the drug of choice at every age, including children, and treatment should not wait for serology.
What you must remember
- Organism: Orientia tsutsugamushi, an obligate intracellular bacterium that infects endothelial cells.
- Vector: larval trombiculid mites, which bite in grass and scrub vegetation, and humans are incidental hosts.
- Eschar: a painless black necrotic ulcer with a red halo at the bite site, which may be missed on a casual examination.
- Clinical picture: fever, lymphadenopathy, rash and hepatosplenomegaly, with the eschar as the key local clue.
- Complications: pneumonitis, meningoencephalitis, myocarditis and shock in severe disease.
- Diagnosis: IgM ELISA or immunofluorescence, with the Weil-Felix test now of limited value.
- Drug of choice: doxycycline for all ages, with azithromycin as the alternative where doxycycline cannot be used.
- Endemic areas: the Himalayan foothills, the northeast and parts of southern India.
A pathway from eschar to treatment
A 7-year-old from a village at the edge of a forest has had fever for five days and a black spot on the thigh. The steps below turn these clues into a treatment decision without delay.
- Look for the eschar: examine the groin, axilla, scalp and thighs carefully, since the painless black spot is easily missed.
- Check the lymph nodes: feel for tender regional nodes, which often lie close to the eschar.
- Send serology: draw IgM ELISA or immunofluorescence on serum, and repeat it later, since early samples can be negative.
- Start empirical treatment: give doxycycline without waiting for the result when the clinical picture fits.
- Watch for organ involvement: check for pneumonitis, altered sensorium, jaundice and shock, which need intensive care.
- Review the response: fever usually settles within a day or two of doxycycline, and a poor response should prompt a review of the diagnosis.
Where the exam tries to catch you
Questions on this topic test the drug of choice, the diagnostic test and the eschar.
- Trap: withholding doxycycline from a child because of age Correct: doxycycline is the drug of choice at all ages, and azithromycin is only an alternative where doxycycline cannot be used.
- Trap: relying on the Weil-Felix test to confirm the diagnosis Correct: it is insensitive and nonspecific, so IgM ELISA or immunofluorescence is preferred.
- Trap: treating the eschar as a simple abscess Correct: a painless black necrotic ulcer is a clue to rickettsial infection, not a collection of pus.
- Trap: thinking scrub typhus spreads from person to person Correct: it is transmitted by the larval mite bite, and humans are incidental hosts.
Frequently asked questions
Which drug is the treatment of choice for scrub typhus in children?
Doxycycline is the treatment of choice for scrub typhus in children, as it is at every age. It is started without waiting for serology when the clinical picture fits. Azithromycin is the alternative for children in whom doxycycline cannot be used.
What is the eschar in scrub typhus?
The eschar in scrub typhus is a painless, black necrotic ulcer with a red halo at the site of the mite bite. It is often seen on the groin, axilla or scalp and may be missed on a casual examination. Its presence in a febrile child strongly suggests rickettsial infection.
Why is the Weil-Felix test no longer preferred for diagnosing scrub typhus?
The Weil-Felix test detects cross-reacting antibodies against Proteus antigens, so it is insensitive and nonspecific for scrub typhus. A negative result early in the illness does not exclude the disease. IgM ELISA or immunofluorescence is preferred for diagnosing scrub typhus.
How is scrub typhus transmitted, and which organism causes it?
Orientia tsutsugamushi causes scrub typhus and is transmitted to humans by the bite of infected larval trombiculid mites, known as chiggers. Humans are incidental hosts and do not spread the infection to one another. The disease is common in scrub vegetation of the Himalayan foothills, the northeast and parts of southern India.
Which features make scrub typhus in children a medical emergency?
Severe scrub typhus can involve the lungs, brain, heart and kidneys, causing pneumonitis, meningoencephalitis, myocarditis and shock. Children with altered sensorium, respiratory distress or jaundice need intensive care. Early empirical doxycycline is central to preventing progression.