Risk Factors for Acquiring Scrub Typhus among the Adults

Abstract

Background: Behavioral and geographical factors may play a role in the acquisition of scrub typhus infection. In this prospective case-control study, we studied the factors associated with infection.

Patients and methods: Consecutive adult patients admitted with scrub typhus infection over 10 months were recruited. For every case, a geographical control from the same area and a gender-matched clinical control admitted with acute febrile illness were enrolled. The risk factors, which included sanitation, environment, activity, and protective measures, were compared between cases and controls using univariable and multivariable conditional logistic regression analysis and expressed as odds ratio (OR) with 95% confidence interval (CI).

Results: The study cohort (n = 225; 132 female) aged 44 ± 17 years comprised of 75 cases and 150 controls from mid to low socioeconomic background. When compared with clinical controls, on univariable conditional regression analysis, cases were more likely to be involved in farming or gardening and less likely to have a toilet within the house. On multivariate regression analysis, only involvement in farming or gardening was associated with infection (OR: 4.2, 95% CI: 1.5-11.5). When compared with geographical controls, on univariable conditional regression analysis, cases were less likely to change undergarments or clothes before sleeping (OR: 3.5, 95% CI: 1.3-9.5) and more likely to have rodents in their house (OR: 2.5, 95% CI: 1-6.4) and rest on grass/mud without a mat (OR: 2.4, 95% CI: 1.1-5.3). On multivariate regression analysis, not changing undergarments or clothes tended to be associated with infection (OR: 2.7, 95% CI: 0.98-7.3).

Conclusion: Certain behavioral factors predisposed our cohort to develop scrub typhus infection. Lifestyle changes may reduce the burden of scrub typhus in South India.

Keywords: Case–control; South India; risk factors; scrub typhus.

Figure 1

Incidence of scrub typhus cases over the study period (January to September 2013) and their relation to rainfall and temperature