Ecological and behavioural risk factors of scrub typhus in central Vietnam: a case-control study

Abstract

Background The risk factors for scrub typhus in Vietnam remain unknown. Scrub typhus caused by Orientia tsutsugamushi often presents as an undifferentiated febrile illness and remains under appreciated due to the limited availability of diagnostic tests. This tropical rickettsial illness is increasingly recognized as an important cause of non-malaria acute undifferentiated fever in Asia. This study aimed to investigate behavioural and ecological related risk factors of scrub typhus to prevent this potentially life-threatening disease in Vietnam. Methods We conducted a clinical hospital-based active surveillance study, and a retrospective residence-enrolment date-age-matched case–control study in Khanh Hoa province, Vietnam, from August 2018 to March 2020. Clinical examinations, polymerase chain reaction and enzyme-linked immunosorbent assay IgM tests were applied to define cases and controls. All enrolled participants filled out a questionnaire including demographic socio-economic status, personal behaviors/protective equipment, habitat connections, land use, and possible exposure to the vector. Multivariable conditional logistic regression was used to define the scrub typhus associated risk factors. Results We identified 44 confirmed cases and matched them with 152 controls. Among cases and controls, the largest age group was the 41–50 years old and males accounted for 61.4% and 42.8%, respectively. There were similarities in demographic characteristics between the two groups, with the exception of occupation. Several factors were significantly associated with acquisition of scrub typhus, including sitting/laying directly on household floor [adjusted OR (aOR) = 4.9, 95% CI: 1.6–15.1, P = 0.006], household with poor sanitation/conditions (aOR = 7.9, 95% CI: 1.9–32.9, P = 0.005), workplace environment with risk (aOR = 3.0, 95% CI: 1.2–7.6, P = 0.020), always observing mice around home (aOR = 3.7, 95% CI: 1.4–9.9, P = 0.008), and use of personal protective equipment in the field (aOR = 0.4, 95% CI: 0.1–1.1, P = 0.076). Conclusions Ecological and household hygiene-related factors were more associated with scrub typhus infection, than individual-level exposure activities in the hyper-endemic area. These findings support local education and allow people to protect themselves from scrub typhus, especially in areas with limitations in diagnostic capacity. Graphical abstract

Prevalence of and factors associated with scrub typhus exposure among the hill tribe population living in high incidence areas in Thailand: a cross-sectional study

“…Similar findings were reported in India [ 37 , 38 ], Laos [ 33 ] and the northeast and southern regions of Thailand [ 35 ], with low education levels being associated with greater risks of scrub typhus infection. In contrast, several studies conducted in Vietnam [ 41 ], Korea [ 42 ], and China [ 40 ] did not show any link between education level and scrub typhus infection. This might be because almost all participants had the same educational level, and thus, there may not be enough statistical power to detect differences.…”

“…Several studies also reported that wearing gloves could protect individuals from scrub typhus infection [ 11 , 45 ]. Other clothing has been reported to be protective against scrub typhus infection, including long sleeve garments, long pants, boots, and socks [ 11 , 40 , 41 , 46 ].…”

Climate influences scrub typhus occurrence in Vellore, Tamil Nadu, India: analysis of a 15-year dataset

“…In this study, females were found to have a higher prevalence of scrub typhus (57.5%) than males and it is almost similar to the reported proportion of 58.7% in Vellore 46 and 51.46% in Guangzhou, Southern China 39 . But a surveillance and case–control study done in Vietnam in 2021 reported less proportion of females being positive for scrub typhus (38.6%) 52 . In multivariate analysis, females had a higher chance of being positive for scrub typhus.…”

Epidemiology, clinical characteristics, diagnosis, and complications of scrub typhus infection in Nepal: a systematic review

“…To prevent the spread of the disease, it is essential to implement precautionary measures aimed at controlling the rodent population in rural areas. According to a study in Vietnam, factors related to ecological and household hygiene were found to have a stronger association with ST infection compared to individual-level exposure activities in the highly endemic area 51 .…”