Risk factors of scrub typhus infection in children and adults in Kerala, south India

Abstract

Objective: To identify the risk factors for acquiring scrub typhus infection among all age group.

Methods: A case-control study was carried out from June to December 2019 in collaboration with the Department of Health Services, Kerala. 136 Of serologically confirmed scrub typhus reported during 2018 were included and 270 age and sex-matched healthy controls were selected randomly from different locations in the same area where the cases were reported. The risk factors identified were compared between cases and controls, using univariate and multivariable logistic regression analysis to identify the risk factors for scrub typhus infection.

Results: Some key factors like house type with individuals residing in houses with concrete roofs are associated with a higher risk of scrub typhus infection compared to tiled roofs (aOR 0.14, 95% CI 0.36-0.56, P=0.005). Housewives exhibit a significantly higher risk (aOR 3.97, 95% CI 2.15-8.94, P=0.038) of scrub typhus infection. Environmental factors, including the presence of rats (aOR 3.48, 95% CI 1.19-6.53, P=0.023), the presence of domestic animals (aOR 2.98, 95% CI 1.67-5.19, P<0.001), wet agricultural fields around the house (aOR 3.64, 95% CI 1.50-6.54, P<0.001), and hygiene practices like not changing clothes after work (aOR 2.64, 95% CI 1.37-4.68, P=0.024), and disposing of the wastes in their own yard (aOR 4.79, 95% CI 3.78-9.55, P=0.043) are identified as significant high-risk factors for scrub typhus infection.

Conclusions: These findings will be very useful to create awareness among the public and to undertake a detailed control strategy for scrub typhus.

Keywords

Chigger mites / Scrub typhus / Case-control study

Conflict of interest statment

We declare that we have no conflict of interest.

Funding

This work was supported by ICMR-VCRC, Puducherry (ID:IM1710).

Authors’ contributions

GR: data acquisition, manuscript writing & editing, NJ: data analysis, interpretation, KR: data acquisition, KK: data acquisition, AK: design, PPS: concepts, design, definition of intellectual content, manuscript preparation.

Publisher’s note

The Publisher of the Journal remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Acknowledgments

We are thankful to our Director, ICMR-VCRC, Puducherry for providing all the necessary facilities, constant encouragement, guidance, and useful suggestions for undertaking this study. We want to express our deep sense of gratitude to all our departmental colleagues. Again authors wish to extend their sincere thanks to DHS Thiruvanthapuram especially to Dr. V. Meenakshy, Additional DHS (PH), Kerala for her guidance and support to undertake this work.

References

[1] Rahi M, Gupte MD, Bhargava A, Varghese GM, Arora R. DHR-ICMR guidelines for diagnosis & management of Rickettsial diseases in India. Indian J Med Res 2015; 141(4): 417-422.

[2] Ibrahim AB. Scrub typhus: A mini review of the the diagnostic challenges. Glob J Res Rev 2021; 8(2): 59.

[3] Kim S, Kim AR, Lim S, Lee SJ, Bae M. Real-world utility of serological tests in patients with suspected scrub typhus in the Republic of Korea: A single-center, retrospective, observational study. Asian Pac J Trop Med 2024; 17(6): 273-280.

[4] Paulraj PS, Renu G, Ranganathan K, Leo VJ, Veeramanoharan R. First sero-prevalence report of scrub typhus from the tribal belts of the Nilgiris district, Tamil Nadu, India. Indian J Med Res 2021; 153(4): 503-507.

[5] Kim DM, Kim KY, Nam HS, Kweon SS, Park MY, Ryu SY. Risk-factors for human infection with Orientia tsutsugamushi: A case-control study in Korea. Clin Microbiol Infect 2008; 14(2): 174-177.

[6] Kweon SS, Choi JS, Lim HS, Kim JR, Kim KY, Ryu SY, et al. A community-based case-control study of behavioral factors associated with scrub typhus during the autumn epidemic season in South Korea. Am J Trop Med Hyg 2009; 80(3): 442-446.

[7] Sharma PK, Ramakrishnan R, Hutin YJ, Barui AK, Manickam P, Kakkar M, et al. Scrub typhus in Darjeeling, India: Opportunities for simple, practical prevention measures. Trans R Soc Trop Med Hyg 2009; 103(11): 1153-1158.

[8] Singh SI, Devi KP, Tilotama R, Ningombam S, Gopalkrishna Y, Singh TB, et al. An outbreak of scrub typhus in Bishnupur district of Manipur, India, 2007. Trop Doct 2010; 40(3): 169-170.

[9] Vallée J, Thaojaikong T, Moore CE, Phetsouvanh R, Richards AL, Souris M, et al. Contrasting spatial distribution and risk factors for past infection with scrub typhus and murine typhus in Vientiane City, Lao PDR. PLoS Negl Trop Dis 2010; 4(12): e909.

[10] Lyu Y, Tian L, Zhang L, Dou X, Wang X, Li W, et al. A case-control study of risk factors associated with scrub typhus infection in Beijing, China. PLoS One 2013 14; 8(5): e63668.

[11] Li T, Yang Z, Dong Z, Wang M. Meteorological factors and risk of scrub typhus in Guangzhou, southern China, 2006-2012. BMC Infect Dis 2014; 14: 139.

[12] Zhang L, Zhao Z, Bi Z, Kou Z, Zhang M, Yang L, et al. Risk factors associated with severe scrub typhus in Shandong, northern China. Int J Infect Dis 2014; 29: 203-207.

[13] Varghese GM, Raj D, Francis MR, Sarkar R, Trowbridge P, Muliyil J. Epidemiology & risk factors of scrub typhus in south India. Indian J Med Res 2016; 144(1): 76-81.

[14] Trowbridge P, Divya P, Premkumar PS, Varghese GM. Prevalence and risk factors for scrub typhus in South India. Trop Med Int Health 2017; 22(5): 576-582.

[15] George T, Rajan SJ, Peter JV, Hansdak SG, Prakash JAJ, Iyyadurai R, et al. Risk factors for acquiring scrub typhus among the adults. J Glob Infect Dis 2018; 10(3): 147-151.

[16] Premraj SS, Mayilananthi K, Krishnan D, Padmanabhan K, Rajasekaran D. Clinical profile and risk factors associated with severe scrub typhus infection among non-ICU patients in semi-urban south India. J Vector Borne Dis 2018; 55(1): 47-51.

[17] Thangaraj JWV, Vasanthapuram R, Machado L, Arunkumar G, Sodha SV, Zaman K, et al. Risk factors for acquiring scrub typhus among children in Deoria and Gorakhpur Districts, Uttar Pradesh, India, 2017. Emerg Infect Dis 2018; 24(12): 2364-2367.

[18] Ramakrishnan D, Nujum ZT, Varghese S, Farook U, Christopher B, Abraham SS, et al. Scrub typhus death: Losing the precious time. SM Trop Med J 2016; 1(2): 1006.

[19] Philip Samuel P, Govindarajan R, Krishnamoorthi R, Rajamannar V. A study on ectoparasites with special reference to chigger mites on rodents/ shrews in scrub typhus endemic areas of Kerala state, India. Entomon 2020; 45: 285-294.

[20] Rose W, Kang G, Verghese VP, Candassamy S, Samuel P, Prakash JJA, et al. Risk factors for acquisition of scrub typhus in children admitted to a tertiary centre and its surrounding districts in South India: A case control study. BMC Infect Dis 2019; 19(1): 665.

[21] Olson JG, Bourgeois AL, Fang RC. Population indices of chiggers (Leptotrombidium deliense) and incidence of scrub typhus in Chinese military personnel, Pescadores Islands of Taiwan, 1976-77. Trans R Soc Trop Med Hyg 1982; 76(1): 85-88.

[22] Khan F, Mittal G, Agarwal RK, Ahmad S, Gupta S, Shadab M, et al. Prevalence of scrub typhus--A cause of concern in Uttarakhand Region, India. Int J Curr Microbiol Appl Sci 2015; 1: 101-109.

[23] Devamani CS, Schmidt WP, Ariyoshi K, Anitha A, Kalaimani S, Prakash JAJ, et al. Risk factors for scrub typhus, murine typhus, and spotted fever seropositivity in urban areas, Rural Plains, and peri-forest hill villages in south India: A cross-sectional study. Am J Trop Med Hyg 2020; 103(1): 238-248.