What is scrub typhus?
Scrub typhus is a mite-born acute infectious disease caused by gram-negative bacteria Orientia tsutsugamushi. The disease is a zoonotic disease that transmits to humans from the bite of mite larvae called “Chiggers” belonging to the Trombiculidae family. Trombiculid mites are small (0.2–0.4 mm) and have a four-stage life cycle: egg, larva (chigger), nymph, and adult. However, only the larval stage of the mite can transmit the bacterium to other human beings. The Trombiculidae mites responsible for Scrub typhus belong to a particular species called Leptotrombidium delicense. Scrub typhus affects people of all ages, including children. Scrub typhus is also known as bush typhus, tsutsugamushi disease, or chigger borne typhus. Incidence of scrub typhus is more prominent in Far East Russia, Japan, and Northern Australia. Thus, those areas are also known as the “tsutsugamushi triangle.” Afghanistan, India, China, Japan, and Indonesia also show the incidence of scrub typhus.
Risk factors and symptoms of Scrub Typhus
The clinical symptoms of scrub typhus are the same for pregnant and non-pregnant women. Scrub typhus has an incubation period of about 5–20 days (mean 10–12 days) after the initial chigger bite. The common areas where chigger bites are the crotch, axillae, genitalia, and neck. A chigger’s bite is painless and leads to the development of a Papule at the site of the bite. The papule dries out and blackens, forming a necrotic lesion of the skin, which is known as an “eschar.”
Upon onset, scrub typhus is associated with the following symptoms:
- Chills and Fever
- Headache
- Infection of the conjunctiva
- Respiratory distress
- Swelling of lymph nodes
- Body aches and muscle pain
After one week, spotted and maculopapular rashes appear, which blenches within a few days. Scrub typhus can lead to multiple health complications if not diagnosed and treated quickly. In severe cases, scrub typhus can lead to:
- Hypotension (low blood pressure)
- Thrombocytopenia (deficiency of platelets in the blood)
- Leucocytosis (increase in white blood cells)
- Hypoxia (difficulty breathing)
- Acute renal failure
- Hypoalbuminemia (deficit of albumin)
- Hepatic dysfunction (liver not working properly)
Diagnosis of Scrub Typhus
When any patient infected with scrub typhus visits a hospital, the physician checks for the above symptoms, upon finding the symptoms aligning with the risk of scrub typhus, the physician goes for diagnostic tests to confirm scrub typhus.
There are two different methods to diagnose Scrub typhus.
1. Direct Method
The direct method involves the isolation and culture of the bacteria in cell lines, including:
- The fibroblast cell line of Mouse
- Cancer cell line
- Kidney cell lines of Baby Hamster
The direct method also involves DNA-based diagnosis using different genetic markers by PCR.
2. Indirect Method
The indirect immuno-based methods include the
- Weil-Felix test
- Immunofluorescence assay (IFA)
- Immunochromatographic test (ICT)
- Indirect Enzyme-Linked Immunosorbent Assay (ELISA) and
Immunoperoxidase assays
Read more about the diagnosis of scrub typhus by reading our article “Diagnosis of Scrub Typhus.”
Effect of Scrub Typhus in Pregnancy
Studies observing the outcome of Scrub typhus in pregnant woman has reported preterm delivery, stillbirth, spontaneous abortion, vertical transmission of scrub typhus to neonates, and intrauterine deaths. A study published by Sudha J Rajan et al. presents the outcomes among pregnant patients with scrub typhus treated at a tertiary care teaching hospital in India. Scrub typhus was diagnosed by clinical criteria and scrub ELISA positivity or an eschar. Out of a total of 738 diagnosed patients, 33 patients were pregnant. The study results involved poor fetal outcomes, including:
• Fetal Loss due to intrauterine deaths and spontaneous abortion
• Preterm Childbirth
• Most of the pregnant women needed intensive care treatment for survival
• Mortality was reported in one patient.
The study concluded that fetal Loss among pregnant women due to scrub typhus could be prevented by increasing awareness among practitioners and patients to carry out early diagnosis and appropriate therapy.
Similarly, another scientific article published by Dr. Preeti Priyadarshani et al. presented a pregnant woman diagnosed with scrub typhus during the third trimester of pregnancy (38 weeks). Before developing scrub typhus, the pregnant women suffered from high-grade fever for 12 days. In addition, the presence of eschar was identified on the foot of the patient.
Ultrasonography revealed that the fetus was experiencing tachycardia distress in utero, and the amniotic fluid volume was too less than expected for gestational age. However, the baby was delivered successfully through the vaginal route without any vertical transmission of scrub typhus symptoms. The study concluded that providing treatment at the right time can prevent fatal outcomes on the fetus and the mother due to scrub typhus.
Treatment of scrub typhus in pregnant women
Since Doxycycline and Chloramphenicol are avoided in pregnant women, Azithromycin becomes the antibiotic drug of choice to treat scrub typhus. Antibiotics show higher efficacy and recovery when given in the early stage of scrub typhus. According to a case study reported by Eun Sil Kim et al., a 500 mg dose of Azithromycin showed successful results in pregnant women. A study published by George Watt et al. found complete recovery from scrub typhus in a 32-week pregnant female who underwent treatment with oral Azithromycin. However, abortion was inevitable. Similarly, another study by Eun-Kyoung Choi and Hynjoo Pai found Oral Azithromycin 500 mg effective in treating two pregnant females (19-week and 24-week) suffering from scrub typhus. However, we need more clinical trials to confirm the effectiveness of Azithromycin in treating scrub typhus among pregnant women.
Reference
- Rajan, S. J., Sathyendra, S., & Mathuram, A. J. (2016). Scrub typhus in pregnancy: Maternal and fetal outcomes. Obstetric medicine, 9(4), 164–166. https://doi.org/10.1177/1753495X16638952
- AIN, Geeta; PRIYADARSHANI, Preeti; SISODIA, Garima. Scrub typhus in third trimester of pregnancy: dilemmas in diagnosis and management. International Journal of Reproduction, Contraception, Obstetrics and Gynecology, [S.l.], v. 10, n. 1, p. 413-415, dec. 2020. ISSN 2320-1789. Available at: <https://www.ijrcog.org/index.php/ijrcog/article/view/9455>. Date accessed: 06 mar. 2022. doi:http://dx.doi.org/10.18203/2320-1770.ijrcog20205813.
- Vorapong Phupong (2010). Pregnancy and scrub typhus. JK Science, Vol. 12 No. 2, April-June 2010. Accessed at
https://www.jkscience.org/archive/volume122/Pregnancy%20and%20Scrub%20Typhus13.pdf - Treatment of Scrub Typhus during Pregnancy : Review of Korean Patients. Accessed at
https://synapse.koreamed.org/upload/synapsedata/pdfdata/1086ic/ic-40-130.pdf - 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. - Watt G, Kantipong P, Jongsakul K, Watcharapichat P, Phulsuksombati D. Azithromycin activities against Orientia tsutsugamushi strains isolated in cases of scrub typhus in Northern Thailand. Antimicrob Agents Chemother. 1999 Nov;43(11):2817-8. doi: 10.1128/AAC.43.11.2817. PMID: 10543774; PMCID: PMC89570.
