Scrub typhus is an endemic disease in South-east Asia and is the most important cause among undifferentiated fevers accounting for about 20-35%. Diagnosis of scrub typhus is a challenge, especially in patients with dengue fever, leptospirosis, rickettsioses, typhoid and malaria as they can present with similar signs and symptoms. Serological tests like rapid immunochromatographic tests and Weil-Felix tests are easy to perform and inexpensive, but lack specificity and sensitivity. The main aim of the study is to screen for scrub typhus by using routine serological tests, ELISA and real time PCR. A total of 32 blood samples suspected to be scrub typhus, were tested for serological assays like rapid immunochromatography, Weil-Felix and ELISA, and real time PCR for identifying 47KDa gene specific for Orienta tsutsugamushi Karp strain. A total of 100 samples were considered, which were collected from patients with fever of unknown origin. A total of 68 samples were found to be positive for various infections ruled out by routine microbiological investigations. Scrub typhus screening was done for the remaining 32, out them 12 (37.5%) samples were positive by rapid immunochromatographic test, 9 (28.1%) samples were tested positive by Weil-Felix agglutination test and 7 (21.8%) samples were positive by ELISA. All the 32 samples were selected for performing real-time polymerase chain reaction (RT-PCR), out of these 20 were positive by real-time PCR, which included the 12 samples positive by rapid immunochromatography method.

Keywords: Weil-Felix, RT- PCR, 47KDa gene, ELISA.

1. Jeong YJ, Kim S, Wook YD, Lee JW, Kim KI, Lee SH. Scrub typhus: clinical, pathologic, and imaging findings. Radiographics. 2007 Jan;27(1):161-72.
2. Walsh DS, Myint KS, Kantipong PA, Jongsakul KR, Watt GE. Orientia tsutsugamushi in peripheral white blood cells of patients with acute scrub typhus. The American journal of tropical medicine and hygiene. 2001 Dec 1;65(6):899-901.
3. Stephen S, Sangeetha B, Ambroise S, Sarangapani K, Gunasekaran D, Hanifah M, Somasundaram S. Outbreak of scrub typhus in Puducherry & Tamil Nadu during cooler months. The Indian journal of medical research. 2015 Nov;142(5):591.
4. Dogra S. Recent Advances in Understanding Pathophysiology of Scrub Typhus 2010.
5. Szyfres B, Acha PN. Zoonoses and Communicable Diseases Common to Man and Animals: Parasitic Zoonoses. Pan American Health Org; 2003 Sep 15.
6. Mahajan SK. Scrub typhus. JAPI. 2005 Nov 7;53(955):269.
7. Kim DM, Park G, Kim HS, Lee JY, Neupane GP, Graves S, Stenos J. Comparison of conventional, nested, and real-time quantitative PCR for diagnosis of scrub typhus. Journal of clinical microbiology. 2011 Feb 1;49(2):607-12.
8. Amy G Rapsang, Prithwis Bhattacharyya. Scrub typhus. Indian Journal of Anaesthesia | Vol. 57| Issue 2 | Mar-Apr 2013. 2. AR Chogle. Diagnosis and Treatment of Scrub Typhus –The Indian Scenario. JAPI • January 2010 • VOL. 58.
9. Huber E, Ji D, Howell L, Zhang Z, Chen HW, Ching WM, Chao CC. Loop-mediated isothermal amplification assay targeting the 47-kDa gene of Orientia tsutsugamushi: a rapid and sensitive alternative to real-time PCR. J Med Microb Diagn. 2012;1(112): 2161-0703.
10. Singh SK, Ram R, Marangmei L, Chakma G. Case series on scrub typhus from a tertiary care hospital of North East India. IOSR J Den Med Sci. 2014; 13:62-4.
11. Order JA. M Vivekanandan, Anna Mani, Yamini Sundara Priya, Ajai Pratap Singh, Samuel Jayakumar, Shashikala Purty. Order. 2010 Jan;58.
12. Narvencar KP, Rodrigues S, Nevrekar RP, Dias L, Dias A, Vaz M, Gomes E. Scrub typhus in patients reporting with acute febrile illness at a tertiary health care institution in Goa. The Indian journal of medical research. 2012 Dec;136(6):1020.
13. Dr. Ravindra K. shravasti, Dr. Vasant B. Jadhav, Dr. Naman Mahesh Shah, Dr. Akshay D. Shah, Dr. Raghunath B. Kulkarni. Study of The Clinico-Laboratory Profile of Sporadic Cases of Scrub Typhus. INDIAN JOURNAL OF APPLIED RESEARCHVolume: 4 | Issue: 11 | November 2014 | ISSN - 2249-555X.
14. Thakur SS, Mahajan SK. Management of scrub typhus.
15. Meena JK, Khandelwal S, Gupta P, Sharma BS. Scrub typhus meningitis: An emerging infectious threat. Age. 2015;2(8):16-3.
16. Song JW, Baek LJ, Lee YJ, Song KJ, Han SH. Seroepidemiologic analysis of acute febrile illness from Korea in 1996. Journal of the Korean Society of Virology. 1998 Dec 1;28(4):377-82.

Vasanthi.R

Professor, Department of Microbiology, Chettinad Hospital and Research Institute, Chennai