Abstract :

Background and aim: Scrub typhus is an acute zoonotic infection caused by Orientis tsutsugamushi and transmitted through the bite of infected chigger mites. It is increasingly recognized as a major cause of acute undifferentiated febrile illness across the Asia–Pacific region. In Sri Lanka, scrub typhus has re-emerged as an important public health concern, yet comprehensive national-level analyses describing its epidemiological trends and distribution remain limited. This study aims to assess the burden, geographical distribution, and temporal trends of scrub typhus in Sri Lanka over a five-year period from 2020 to 2024.

Method: A retrospective descriptive study was conducted using secondary surveillance data obtained from the Weekly Return of Communicable Diseases (WRCD) published by the Epidemiology Unit of the Ministry of Health, Sri Lanka. Reported scrub typhus cases from January 2020 to December 2024 were extracted and analyzed. Data were summarized using frequencies and percentages to describe annual trends and district-wise distribution of cases.

Results: A total of 5,947 scrub typhus cases were reported nationally during the five-year study period. The annual trend demonstrated fluctuations, with a temporary decline in reported cases in 2021, likely influenced by disruptions to healthcare services and disease surveillance during the COVID-19 pandemic. However, case numbers increased again in the subsequent years, indicating a persistent endemic presence. The geographical distribution of cases showed marked heterogeneity, with the northern district of Jaffna accounting for more than 53% of the total national burden. Other districts reported relatively lower case numbers, suggesting possible variations in ecological exposure, diagnostic capacity, and clinical awareness.

Conclusion: Scrub typhus remains an important public health concern in Sri Lanka with a sustained burden and notable geographical clustering. Strengthening laboratory diagnostic capacity, enhancing clinician awareness, improving surveillance systems, and implementing targeted preventive measures for high-risk occupational groups are essential to improve early detection and reduce the disease burden. Geographically stratified surveillance and focused interventions in high-risk districts are recommended to strengthen control efforts.

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Keywords :

Disease surveillance, Epidemiology, Scrub Typhus in Sri Lanka, Zoonotic infection

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References :

1. Bonell A, Lubell Y, Newton PN, Crump JA, Paris DH. Estimating the burden of scrub typhus: A systematic review. PLoS Negl Trop Dis. 2017;11(9):e0005838. https://doi.org/10.1371/journal.pntd.0005838
2. Paris DH, Shelite TR, Day NPJ, Walker DH. Unresolved problems related to scrub typhus: A seriously neglected life-threatening disease. Am J Trop Med Hyg. 2013;89(2):301-7. https://doi.org/10.4269/ajtmh.13-0064
3. Kelly DJ, Fuerst PA, Ching WM, Richards AL. Scrub typhus: The geographic distribution of phenotypic and genotypic variants of Orientia tsutsugamushi. Clin Infect Dis. 2009;48(Suppl 3):S203-30. https://doi.org/10.1086/59657
4. Xu G, Walker DH, Jupiter D, Melby PC, Arcari CM. A review of the global epidemiology of scrub typhus. PLoS Negl Trop Dis. 2017;11(11):e0006062. https://doi.org/10.1371/journal.pntd.0006062
5. Premaratna R, Chandrasena TGAN, Dassayake AS, Loftis AD, Dasch GA, de Silva HJ. Scrub typhus among patients with acute febrile illness attending a tertiary care hospital in Sri Lanka. Trans R Soc Trop Med Hyg. 2006;100(6):554-9. https://doi.org/10.1016/j.trstmh.2005.08.009
6. Epidemiology Unit, Ministry of Health Sri Lanka. Weekly Epidemiological Report and Communicable Disease Surveillance Data. Colombo: Ministry of Health; 2020–2024. https://www.epid.gov.lk
7. Watt G, Parola P. Scrub typhus and tropical rickettsioses. Curr Opin Infect Dis. 2003;16(5):429–36. https://doi.org/10.1097/00001432-200310000-00009
8. Taylor AJ, Paris DH, Newton PN. A systematic review of the mortality from untreated scrub typhus. PLoS Negl Trop Dis. 2015;9(8):e0003971. https://doi.org/10.1371/journal.pntd.0003971
9. Moynihan R, Sanders S, Michaleff ZA, Scott AM, Clark J, To EJ, et al. Impact of COVID-19 pandemic on utilisation of healthcare services: a systematic review. BMJ Open. 2021;11(3):e045343. https://doi.org/10.1136/bmjopen-2020-045343
10. World Health Organization. The impact of the COVID-19 pandemic on essential health services. Geneva: WHO; 2020. https://www.who.int/publications/i/item/10665-332240
11. Walker DH. Scrub typhus—scientific neglect, ever-widening impact. N Engl J Med. 2016;375(10):913–5. https://doi.org/10.1056/NEJMp1608499
12. Elliott I, Pearson I, Dahal P, Thomas NV, Roberts T, Newton PN. Scrub typhus ecology: a systematic review of Orientia in vectors and hosts. Parasit Vectors. 2019;12:513. https://doi.org/10.1186/s13071-019-3751-x
13. Wei Y, Huang Y, Luo L, Xiao X, Liu L, Yang Z. Rapid increase of scrub typhus incidence in mainland China. PLoS Negl Trop Dis. 2017;11(11):e0006069. https://doi.org/10.1371/journal.pntd.0006069
14. Rapsang AG, Bhattacharyya P. Scrub typhus. Indian J Anaesth. 2013;57(2):127–34. https://doi.org/10.4103/0019-5049.111835
15. Blacksell SD, Bryant NJ, Paris DH, Doust JA, Sakoda Y, Day NPJ. Scrub typhus serologic testing with the indirect immunofluorescence method as the gold standard: a lack of consensus leads to a lot of confusion. Clin Infect Dis. 2007;44(3):391–401. https://doi.org/10.1086/510585