Introduction
Scrub typhus is a form of typhus fever caused by Orientia tsutsugamushi. The causative agent is an intracellular parasite first identified in Japan in 1930. Scrub typhus is synonymous with bush, jungle, or mite typhus. It is endemic in Northern Japan, Eastern Russia, Northern Australia, Pakistan, and Afghanistan. These are the regions that form the tsutsugamushi triangle. Most of the scrub typhus cases are seen in rural areas of Southeast Asia, China, Indonesia, India, Japan, and northern Australia. In India, the disease is seen mainly in the Southern states of Andhra Pradesh and Tamil Nadu. People traveling to these places, especially the rural parts, should be careful of the mites.
Causes
Scrub typhus is a zoonotic disease caused by the Gram-negative bacterium Orientia tsutsugamushi, which belongs to the Rickettsiaceae family.
Orientia tsutsugamushi is an intracellular pathogen with three primary strains Karp, Kato, and Gilliam. In addition, many antigenic strains have been identified from the original three strains over the years. However, infection with one pathogen strain does not confer immunity against the others. Thus, there are no licensed vaccines at present to treat scrub typhus.
Scrub typhus passes to other people through the bites of chigger (infected larval form) of the trombiculid mite, particularly Leptotrombidium delicense. Trombiculid mites are small (0.2–0.4 mm) and have a four-stage life cycle: egg, larva (chigger), nymph, and adult. Trombiculid mites feed on the early stages of small arthropods whose larvae are infected by the parasites. These animals are found predominantly in areas with heavy scrub vegetation.
Signs, Symptoms, and Clinical Presentation
Scrub typhus is transmitted only by vectors and not from person to person. The incubation period of scrub typhus is about 5–20 days (mean 10–12 days) after the initial chigger bite.
The diagnosis of scrub typhus is quite complicated because there is a significant overlap between its symptoms and other infectious diseases such as dengue fever, paratyphoid, pyrexia of unknown origin (PUO), and others. Since it has a lot of nonspecific clinical signs and symptoms, it is often misdiagnosed, especially in low and middle-income countries. We can attribute this to factors like limited awareness about the disease and lack of facilities for diagnosis in these countries.
The signs and symptoms of scrub typhus in children can be as follows:
- headache
- fever
- cough
- vomiting
- drowsiness
- muscle pain
- shin pain
- abdominal pain
- chills
- shortness of breath
- generalized body swelling
- generalized rash
- splenomegaly (enlarged spleen)
- lymphadenopathies (enlarged lymph nodes)
- intravascular coagulation (clotting of blood in the blood vessels)
- mental changes like confusion
- coma.
The symptoms usually start to manifest within ten days of being bitten by the trombiculid mites. The first sign is often a tiny, raised mark at the site of the bite. This then dries out and blackens, forming a necrotic lesion of the skin, which is known as an “eschar.” The child might also feel a rash around the site of the eschar. An eschar is present in about half of infected children and is often an important indication for the diagnosis of scrub typhus.
The exact incidence of the disease is not known. This results from the lack of availability of diagnostic facilities in most of the affected regions. The characteristic eschar helps diagnose clinically, although it might be challenging to identify in dark-skinned children. The eschar can also be missed if it is present in areas that are often covered, which happens quite frequently. The bite is also painless, and the mites are very small, almost invisible to the naked eye. These factors make it difficult to get a bite history when taking the child’s medical history. An extra effort must be made to search for the eschar. Otherwise, it would be missed. If your child develops the symptoms listed above, mainly if they have recently visited
any places known to be endemic for the disease, make sure you take them to the hospital immediately.
Prevention of scrub typhus in Children
There is currently no officially approved vaccine to prevent this disease, but research is still on in this area.
Children and adults can prevent the disease by avoiding contact with infected mites and keeping their surroundings clean. For example, suppose you are traveling to regions where the condition is familiar. In that case, you should avoid places with a lot of vegetation because the vegetation could be harboring the mites. Make sure your children wear clothes that cover their hands and legs. Always spray EPA registered insect repellents on your clothes. However, before applying insect repellents to the skin and face of children, consulting with a physician is highly advised. Adults can use EPA-registered insect repellents directly on the skin and face. If you use a baby carrier to carry your baby, make sure the carrier is clean and has mosquito netting.
Permethrin and permethrin-based items are also effective in protecting children against scrub typhus. Permethrin kills the mites so that it can be applied to your children’s clothes, boots, and camping gear. It should, however, not be applied directly to the skin. Instead, it is meant to treat clothing. In addition, people who use sunscreen before going out can apply insect repellent after applying sunscreen to their bodies.
Treatment
If left undiagnosed and untreated, scrub typhus can cause fatal outcomes. For example, there might be an organ failure like the liver and kidneys in severe cases and excessive bleeding. These can lead to death if treatment is not provided at the right time. Unfortunately, there are no licensed vaccines to treat scrub typhus at present.
Antibiotics have shown efficacy in reducing the death rate. Some of the common drugs used in its treatment are doxycycline, tetracycline, rifampicin, and azithromycin. Doxycycline and tetracycline are the most common. In children, azithromycin is an excellent alternative to doxycycline and tetracycline.
Children whose lungs have been affected due to scrub typhus, leading to acute respiratory distress syndrome (ARDS), may require the infected child to be placed on ventilators and, in some cases, admitted into the Paediatric Intensive Care Unit (PICU).
Conclusion
Scrub typhus is a potentially life-threatening disease with nonspecific symptoms. In places where it is endemic, one should always suspect it in children who show symptoms like fever coupled with headache, abdominal pain, vomiting, and clinical manifestations suggestive of hepatitis, myocarditis, or meningitis. This is regardless of the presence of an eschar. Health complications associated with Scrub Typhus are hepatitis, acute kidney injury, meningitis, and acute respiratory distress syndrome. Therefore, it is crucial to identify these symptoms and visit a physician because early initiation of treatment dramatically reduces the rate of mortality.
References
- Tseng BY, Yang HH, Liou JH, Chen LK, Hsu YH. Immunohistochemical study of scrub typhus: a report of two cases. Kaohsiung J Med Sci. 2008 Feb;24(2):92-8. doi: 10.1016/S1607-551X(08)70103-7. PMID: 18281226.
- Seong SY, Choi MS, Kim IS. Orientia tsutsugamushi infection: overview and immune responses. Microbes Infect. 2001 Jan;3(1):11-21. doi: 10.1016/s1286-4579(00)01352-6. PMID: 11226850.
- Rose W. Scrub typhus in children. Curr Med Issues [serial online] 2017 [cited 2022 Feb 28]; 15:90-4. Available from:
https://www.cmijournal.org/text.asp?2017/15/2/90/206516 - Scrub typhus primary prevention. Accessed at
https://www.wikidoc.org/index.php/Scrub_typhus_primary_prevention - Scrub Typhus. Accessed at https://www.cdc.gov/typhus/scrub/index.html#:~:text=Scrub%20typhus%2C%20also%20known%20as,body%20aches%2C%20and%20sometimes%20rash.
