Molecular Epidemiology and Genetic Diversity of Orientia tsutsugamushi from Patients with Scrub Typhus in 3 Regions of India - Volume 21, Number 1—January 2015 - Emerging Infectious Disease journal - CDC
Volume 21, Number 1—January 2015
Molecular Epidemiology and Genetic Diversity of Orientia tsutsugamushi from Patients with Scrub Typhus in 3 Regions of India
Scrub typhus is a vector-borne, acute febrile illness caused by Orientia tsutsugamushi, an obligate intracellular, gram-negative bacterium. Scrub typhus is widespread in the Asia-Pacific region, known as the “tsutsugamushi triangle.” Mite larvae, or chiggers, of the genus Leptotrombidium transmit the causative bacteria to humans through their bite. The infection is maintained in nature through transovarial transmission in the vector and a reservoir in small mammals (1,2). Clinical signs and symptoms of scrub typhus in humans are largely nonspecific, and if infection is not treated promptly and appropriately, it carries a high mortality rate (3).
The Orientia genome has a high degree of plasticity and is considered to be the most highly repetitive bacterial genome sequenced (4). This diversity is a result of high numbers of intragenomic deletions, duplications, and rearrangements with transposable and conjugative elements. These recombinations and rearrangements are unlikely to occur in dead-end hosts, but the details of this process are unclear (5).
Clarifying the epidemiology and genetic diversity of O. tsutsugamushi strains is essential to the development of rapid diagnostics and vaccines in disease-endemic areas. These efforts would also help in the early recognition and treatment of the disease. Currently, the most widely used method for strain classification is sequence analysis of the 56-kDa type-specific antigen (TSA), an immunodominant outer membrane protein unique to O. tsutsugamushi. With an open reading frame (ORF) of ≈1,600 bp, the 56-kDa TSA contains 516–541 amino acids and is involved in host cell invasion through the binding of fibronectin (6). Four hypervariable domains in this region, variable domains (VD) I–IV, are responsible for the large degree of antigenic variation in this gene. The direct interaction with the host, uniqueness to O. tsutsugamushi, and high level of variability make this protein an attractive target for studying the genetic variation among strains. This region is also highly immunogenic, making it a potential candidate as a vaccine target.
The process of conventional serotyping was a complex procedure, requiring reference serum samples and antigens, and is of limited use today. Greater diversity among the strains has been revealed by using molecular genotyping methods. Antigenic variations in O. tsutsugamushi from patients and rodents in different scrub typhus–endemic regions have been reported by testing using the 56-kDa TSA, which has led to identification of several new subtypes (1), such as Japanese Gilliam, Japanese Karp, Kawasaki, Kuroki, and Shimokoshi, in addition to the previously described prototypes Karp, Kato, and Gilliam (7,8).
Given the broad endemicity of scrub typhus in the Asia-Pacific region and variations in clinical manifestations that may be attributable to strain variation, thorough investigation into the regional distribution of genotypes is warranted. This study was conducted to identify the circulating 56-kDa antigen genotypes in 3 scrub typhus–endemic geographic regions of India: South India, Northern India, and Northeast India.
Dr. Varghese is professor of infectious diseases at Christian Medical College, Vellore, India. His research includes the epidemiology (including molecular epidemiology), pathogenesis, early recognition, and management of rickettsial infections, particularly scrub typhus.
This work was supported by the Indian Council of Medical Research (no. 30/3/16/2008/ECD-II).
- 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 .
- Wongprompitak P, Anukool W, Wongsawat E, Silpasakorn S, Duong V, Buchy P, Broad-coverage molecular epidemiology of Orientia tsutsugamushiin Thailand. Infect Genet Evol. 2013;15:53–8.
- Mathai E, Lloyd G, Cherian T, Abraham OC, Cherian AM. Serological evidence for the continued presence of human rickettsioses in southern India.Ann Trop Med Parasitol. 2001;95:395–8 .
- Cho NH, Kim HR, Lee JH, Kim SY, Kim J, Cha S, The Orientia tsutsugamushi genome reveals massive proliferation of conjugative type IV secretion system and host-cell interaction genes. Proc Natl Acad Sci U S A. 2007;104:7981–6.
- Duong V, Mai TT, Blasdell K. Lo le V, Morvan C, Lay S, et al. Molecular epidemiology of Orientia tsutsugamushi in Cambodia and Central Vietnam reveals a broad region-wide genetic diversity. Infect Genet Evol. 2013;15:35–42.
- Lin PR, Tsai HP, Tsui PY, Weng MH, Kuo MD, Lin HC, Genetic typing, based on the 56-kilodalton type specific antigen gene, of Orientia tsutsugamushi strains isolated from chiggers collected from wild-caught rodents in Taiwan. Appl Environ Microbiol. 2011;77:3398–405 .
- Nakayama K, Kurokawa K, Fukuhara M, Urakami H, Yamamoto S, Yamazaki K, Genome comparison and phylogenetic analysis of Orientia tsutsugamushi strains. DNA Res. 2010;17:281–91.
- Yang H-H, Huang I-T, Lin C-H, Chen T-Y, Chen L-K. New genotypes of Orientia tsutsugamushi isolated from humans in eastern Taiwan. PLoS ONE.2012;7:e46997.
- Mahajan SK, Rolain JM, Kashyap R, Bakshi D, Sharma V, Prasher BS, Scrub typhus in Himalayas. Emerg Infect Dis. 2006;12:1590–2.
- Tamura K, Peterson D, Peterson N, Stecher G, Nei M, Kumar S. MEGA5: molecular evolutionary genetics analysis using maximum likelihood, evolutionary distance, and maximum parsimony methods. Mol Biol Evol. 2011;28:2731–9.
- Isaac R, Varghese GM, Mathai E, Manjula J, Joseph I. Scrub typhus: prevalence and diagnostic issues in rural southern India. Clin Infect Dis.2004;39:1395–6.
- Chrispal A, Boorugu H, Gopinath KG, Prakash JA, Chandy S, Abraham OC, Scrub typhus: an unrecognized threat in South India—clinical profile and predictors of mortality. Trop Doct. 2010;40:129–33.
- Mathai E, Rolain JM, Verghese GM, Abraham OC, Mathai D, Mathai M, Outbreak of scrub typhus in southern India during the cooler months. Ann N Y Acad Sci. 2003;990:359–64 .
- Sharma A, Mahajan S, Gupta ML, Kanga A, Sharma V. Investigation of an outbreak of scrub typhus in Himalayan region of India. Jpn J Infect Dis.2005;58:208–10 .
- Kumar K, Saxena VK, Thomas TG, Lal S. Outbreak investigation of scrub typhus in Himachal Pradesh (India). J Commun Dis. 2004;36:277–83.
- Dass R, Deka NM, Duwarah SG, Barman H, Hoque R, Mili D, Characteristics of pediatric scrub typhus during an outbreak in the North Eastern region of India: peculiarities in clinical presentation, laboratory findings and complications. Indian J Pediatr. 2011;78:1365–70 .
- Goswami D, Hing A, Das A, Lyngdoh M. Scrub typhus complicated by acute respiratory distress syndrome and acute liver failure: a case report from Northeast India. Int J Infect Dis. 2013;17:e644–5.
- Saifudheen K, Kumar KG, Jose J, Veena V, Gafoor VA. First case of scrub typhus with meningoencephalitis from Kerala: an emerging infectious threat. Ann Indian Acad Neurol. 2012;15:141–4.
- Boorugu H, Dinaker M, Roy ND, Jude JA. Reporting a case of scrub typhus from Andhra Pradesh. J Assoc Physicians India. 2010;58:520 .
- Batra HV. Spotted fevers and typhus fevers in Tamil Nadu. Indian J Med Res. 2007;126:101–3 .
- Viswanathan S, Muthu V, Iqbal N, Remalayam B, George T. Scrub typhus meningitis in South India—a retrospective study. PLoS ONE. 2013;8:e66595.
- Althaf A, Kumar KK, Suni KA, Farook MU. A study on scrub typhus in a tertiary care hospital. Kuwait Med J. 2008;3:11–4.
- Khan SA, Dutta P, Khan AM, Topno R, Borah J, Chowdhury P, Re-emergence of scrub typhus in northeast India. Int J Infect Dis. 2012;16:e889–90.
- Gurung S, Pradhan J, Bhutia PY. Out break of scrub typhus in North East Himalayan region- Sikkim: an emerging threat. Indian J Med Microbiol.2013;31:72–4.
- Murdoch DR, Woods CW, Zimmerman MD, Dull PM, Belbase RH, Keenan AJ, The etiology of febrile illness in adults presenting to Patan hospital in Kathmandu, Nepal. Am J Trop Med Hyg. 2004;70:670–5 .
- World Health Organization. Frequently asked questions: scrub typhus [cited 2013 Oct 1].http://www.searo.who.int/entity/emerging_diseases/CDS_faq_Scrub_Typhus.pdf
- Enatsu T, Urakami H, Tamura A. Phylogenetic analysis of Orientia tsutsugamushi strains based on the sequence homologies of 56-kDa type-specific antigen genes. FEMS Microbiol Lett. 1999;180:163–9.
- Ohashi N, Nashimoto H, Ikeda H, Tamura A. Diversity of immunodominant 56-kDa type-specific antigen (TSA) of Rickettsia tsutsugamushi: sequence and comparative analyses of the genes encoding TSA homologues from four antigenic variants. J Biol Chem. 1992;267:12728–35 .
- Manosroi J, Chutipongvivate S, Auwanit W, Manosroi A. Determination and geographic distribution of Orientia tsutsugamushi serotypes in Thailand by nested polymerase chain reaction. Diagn Microbiol Infect Dis. 2006;55:185–90.
- Lu HY, Tsai KH, Yu SK, Cheng CH, Yang JS, Su CL, Phylogenetic analysis of 56-kDa type-specific antigen gene of Orientia tsutsugamushi isolates in Taiwan. Am J Trop Med Hyg. 2010;83:658–63 .
- Tamura A, Yamamoto N, Koyama S, Makisaka Y, Takahashi M, Urabe K, Epidemiological survey of Orientia tsutsugamushi distribution in field rodents in Saitama Prefecture, Japan, and discovery of a new type. Microbiol Immunol. 2001;45:439–46.
- Qiang Y, Tamura A, Urakami H, Makisaka Y, Koyama S, Fukuhara M, Phylogenetic characterization of Orientia tsutsugamushi isolated in Taiwan according to the sequence homologies of 56-kDa type-specific antigen genes. Microbiol Immunol. 2003;47:577–83.
- Seong SY, Park SG, Huh MS, Jang WJ, Choi MS, Chang WH, T-track PCR fingerprinting for the rapid detection of genetic polymorphism. FEMS Microbiol Lett. 1997;152:37–44.
- Bakshi D, Singhal P, Mahajan SK, Subramaniam P, Tuteja U, Batra HV. Development of a real-time PCR assay for the diagnosis of scrub typhus cases in India and evidence of the prevalence of new genotype of O. tsutsugamushi. Acta Trop. 2007;104:63–71.
- Blacksell SD, Luksameetanasan R, Kalambaheti T, Aukkanit N, Paris DH, McGready R, Genetic typing of the 56-kDa type-specific antigen gene of contemporary Orientia tsutsugamushi isolates causing human scrub typhus at two sites in north-eastern and western Thailand. FEMS Immunol Med Microbiol. 2008;52:335–42.
- Kim DM, Yun NR, Neupane GP, Shin SH, Ryu SY, Yoon HJ, Differences in clinical features according to Boryoung and Karp genotypes of Orientia tsutsugamushi. PLoS ONE. 2011;6:e22731.
- Chu H, Park SH, Kim EJ, Hwang KJ, Shim SK, Park S, Phylogenetic clustering of 4 prevalent virulence genes in Orientia tsutsugamushi isolates from human patients. J Microbiol. 2010;48:124–8.
Suggested citation for this article: Varghese GM, Janardhanan J, Mahajan SK, Tariang D, Trowbridge P, Prakash JAJ, et al. Molecular epidemiology and genetic diversity of Orientia tsutsugamushi from patients with scrub typhus in 3 regions of India. Emerg Infect Dis [Internet]. 2015 Jan [date cited].http://dx.doi.org/10.3201/eid2101.140580