Rickettsial diseases and particularly, scrub typhus is one of the oldest recognized vector transmitted zoonosis [1]. The World Health Organization has reported scrub typhus one of the world’s most under diagnosed and under reported disease that often requires hospitalization. Better understanding of the vectors, its outbreaks and its pathogenesis is required to control human outbreaks within and beyond its recognized regions of endemicity [2].

Scrub typhus is endemic to a part of world known as the “tsutsugamushi triangle’’ which extends from northern Japan and far-eastern Russia in the north, to northern Australia in the south, and to Pakistan and Afghanistan in the west [2]. In India, scrub typhus has been documented from the states of Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Rajasthan, Assam, West Bengal, Maharashtra, Kerala and Tamil Nadu [3].

Himachal Pradesh is a mountainous state in northern India, situated at an altitude between 350-6816 meters above mean sea level. During the rainy seasons, areas of lower altitudes experience an average temperature between 20ºC to 35ºC which is suitable for the spread of arthropod vector. Maximum number of the cases are being reported between the months of July to November [4].

Scrub typhus is a well documented disease in the state of Himachal Pradesh, but there have been no Climate and Environmental studies on antibody prevalence and factors associated with the exposure to Orientia tsutsugamushi in the paediatric age group population. Therefore, this study was done to study the Climate and Environmental factors in the new diagnosed cases of scrub typhus.

Aims and Objectives

To study the Climate and Environmental factors in the new diagnosed cases of scrub typhus and risk factors in paediatric population.           

This study was conducted in the department of Paediatrics and Microbiology, Indira Gandhi Medical College, Shimla, a tertiary care teaching institute in Himachal Pradesh. 

• Duration of study: From 1^st June 2017   to  30^th Nov 2018

• Study Design: Cross-sectional Sero-Epidemiological Study

• Ethical Clearance: Approval from the Institutional ethical committee of Indira Gandhi Medical College Shimla

• Financial Assistance:  As part of Institutional intramural grant

Study Population             

The study participants consisted of all 102 newly diagnosed paediatric cases of scrub typhus, admitted in pediatric ward of IGMC Hospital Shimla based on positive IgM against scrub typhus during the study period.

Exclusion Criteria 

• The study subjects having concomitant HIV, Malaria, Tuberculosis, Hepatitis, Typhoid and Acinetobacter septicaemia

• Participants in the control group B and group C having febrile illness during the last three months

• Participants or their parents who are not willing to participate in the study

Statistical Analysis

Data from the case record files was recorded on a Microsoft excel spreadsheet. Statistical analysis was performed using Epi Info 7. All discrete variables were expressed as percentages. 

In the present study, among 102 newly diagnosed cases of Scrub Typus, 57 (55.9%) were males while 45 (44.1%) were females. 39 (38.2%) were in the age group of 1-10 years while 63 (61.8%) were in the age group of 11-18 years.

IGMC being a tertiary care teaching hospital, receive referral from the adjoining districts of the state. The maximum number of patients 47 (46.1%) belonged to Shimla district, followed by Solan 19(18.6%), Mandi 14(13.7%), Bilaspur 10(9.8%), Sirmaur 5(4.9%), Kullu 4(3.9%), Hamirpur 1(0.9%) and others 2(1.9%) respectively. During the study period no patient of suspected or confirmed Scrub typhus was reported from Kinnaur as well as from Lahaul and Spiti (L&S) districts of HP which are situated at a height of 3000 metre above mean sea level. All of the study subjects were residing within the altitude of 350 metre to 2200 metre above mean sea level. 

Majority 45 (44.1%) of cases were diagnosed in the month of September, followed by 35(34.3%) in the month of October, 12(11.8%) in the month of August and only 4(3.9%) in the month of November with decreasing trend corresponding to the onset of winters as Only 6 (5.9%) cases were found in rest of the months.

Table 1: Various Climatic Risk Factors for Scrub Typhus in Study Population

Based on the Koppen-Geiger Climate Classification, the State of Himachal Pradesh is divided into the following four climatic zones namely a) Hot dry summer b) Humid sub-tropical c) Sub-tropical highland d) Sub-tropical highland oceanic. Majority of scrub typhus cases 86(84.3%) were reported from humid subtropical climate in this study.

Altitude of Himachal Pradesh ranges between 350 m to 6816 m. Further subdivision of the study population based on the height above mean sea level, range below 1500 metre, between 1500-2000 metre, above 2000 metre, 51(50%) Scrub Typhus cases were reported from altitude range below 1500 metre in this study.Based on the average annual rainfall, study population was divided into three zones below1500mm/yr, between 1500-2000mm/yr and above 2000mm/yr, 75.5% (77) Cases were reported from climate zone with annual rainfall below 1500mm/yr. Majority of scrub typhus cases 38(37.3%%) were recorded from the areas with average temperature >20 degree centigrade.

Scrub typhus shows seasonal trends in the present study, Majority 45 (44.1%) of cases were diagnosed in the month of September, followed by 35(34.3%) in the month of October, 12(11.8%) in the month of August and only 4(3.9%) in the month of November with decreasing trend corresponding to the onset of winters as Only 6 (5.9%) cases were found in rest of the months. The incidence of cases in our study agrees with a study from South Korea conducted by Kweon Sun-Seog et al. [5] Digra et al. [6] and Mahajan et al. [7]           

Majority of scrub typhus cases 86(84.3%) were reported from humid subtropical climate in this study. 51(50%) Scrub Typhus cases were reported from altitude range below 1500 metre in this study. 75.5% (77) Cases were reported from climate zone with annual rainfall below 1500mm/yr. Majority of scrub typhus cases 38(37.3%%) were recorded from the areas with average temperature >20 degree centigrade.These findings were consistant with the studies done by  Mathai E et al. [8], Li T et al. [10] and Kwak J et al., (2015).

Scrub typhus is endemic and documented zoonosis in the state of Himachal Pradesh as the climatic and geographical conditions are conducive for spread of vector of the scrub typhus. At the onset of monsoon rural children and public should be educated, through health education campaigns in schools and in media regarding the prevention of risk factors associated with scrub typhus, to reduce the morbidity and mortality associated with this disease.

To determine the climatic risk factors for scrub typhus there is an urgent need of well-designed multi-centric study to elaborate on the decadal change in the climate, temperature, rainfall and humidity.

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