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Table of Contents
Year : 2021  |  Volume : 58  |  Issue : 4  |  Page : 323-328

Scrub typhus: An under-reported and emerging threat - hospital based study from central and eastern Uttar Pradesh, India

1 Department of Microbiology, Dr. Ram Manohar Lohia Institute of Medical Sciences, Lucknow, India
2 Amity Institute of Biotechnology, Amity University, Lucknow, India
3 Department of Medicine, Dr. Ram Manohar Lohia Institute of Medical Sciences, Lucknow, India

Date of Submission27-Apr-2020
Date of Acceptance02-Sep-2020
Date of Web Publication25-Mar-2022

Correspondence Address:
Dr Vineeta Mittal
Department of Microbiology, Dr. Ram Manohar Lohia Institute of Medical Sciences, Lucknow
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0972-9062.318311

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Background & objectives: Scrub typhus is a zoonotic rickettsial disease that is transmitted by the bite of the larval stage (chiggers) of trombiculid mites. The aim of this study was to determine the existence of scrub typhus in central and eastern Uttar Pradesh, India in patients with acute febrile illness (AFI) presenting to a super specialty tertiary level institute.
Methods: This prospective hospital-based study was conducted for a period of one year, from August 2018 to July 2019. About 2–5 mL of blood samples, along with clinical, epidemiological, and demographic data from a total of 125 patients presenting with acute febrile illness to outpatient and inpatient departments, were collected. ELISA testing tested the sera from blood samples for IgM antibodies against scrub typhus. Samples were also tested for dengue, leptospirosis, malaria and typhoid.
Results: During the study period, out of a total of 125 samples collected, 20% were found positive for IgM antibodies against scrub typhus. Demographically higher positivity was found in males, older age group, and in rural area. Rainfall was found to be important epidemiological parameter for presence of scrub typhus. Co-infection with dengue, leptospirosis and malaria was found.
Interpretation & conclusion: Scrub typhus is found to be an important cause of acute febrile illness. It is necessary to include it in differential diagnosis of AFI cases even in absence of eschar. Diagnostic facilities of this as a screening test should be started in primary care centers or community health centers of rural areas of districts of central and eastern Uttar Pradesh, India.

Keywords: Acute febrile illness; Central and Eastern Uttar Pradesh; ELISA, Scrub typhus

How to cite this article:
Mittal V, Singh P, Shukla S, Karoli R. Scrub typhus: An under-reported and emerging threat - hospital based study from central and eastern Uttar Pradesh, India. J Vector Borne Dis 2021;58:323-8

How to cite this URL:
Mittal V, Singh P, Shukla S, Karoli R. Scrub typhus: An under-reported and emerging threat - hospital based study from central and eastern Uttar Pradesh, India. J Vector Borne Dis [serial online] 2021 [cited 2022 May 21];58:323-8. Available from: https://www.jvbd.org/text.asp?2021/58/4/323/318311

  Introduction Top

Scrub typhus is a zoonotic rickettsial disease caused by Orientia tsutsugamushi. The larvae (chiggers) of trombiculid mites act as vector and reservoir of the bacteria. Infected chiggers are particularly found in areas of heavy shrubs during wet season, when mites lay eggs[2]. The clinical presentation of scrub typhus may mimic tropical febrile illnesses such as malaria, dengue fever, typhoid fever and leptospirosis[3]. Most of the patients present with nonspecific manifestations. An eschar may develop at the site of chigger bite, which is highly suggestive of scrub typhus[4]. About one third of patients with scrub typhus infection have evidence of organ dysfunction[5].

In southern India, scrub typus was a well-established cause of acute febrile illness, but in northern India it was reported from Delhi, Rajasthan, Punjab, Himachal Pradesh, Uttarakhand and western Uttar Pradesh (UP). It is an emerging threat for healthcare particularly in Uttar Pradesh state due to very few recent studies from this region and lack of suspicion among clinicians[6],[7],[8]. It is under reported and under diagnosed in central and eastern UP due to lack of awareness among physicians and lack of diagnostic facilities especially at primary or secondary health care level. Hardly few tertiary care level hospitals in UP have diagnostic facility for scrub typhus testing. In our study, we have attempted to determine the existence of scrub typhus in central and eastern UP.

  Material & Methods Top

This hospital-based study was conducted in a tertiary care institute from central UP for a period of one year, from August 2018 to July 2019. Inclusion criteria were the patients having acute onset fever of less than 10 days duration with chills, headache, muscle pain, eschar, haemorrhages including sub-conjunctival haemorrhage, jaundice, cough, breathlessness, albuminuria or signs of meningeal irritation. About 2–5 ml of blood sample was drawn from a total of 125 patients presenting to various outpatient and inpatient departments of the institute along with detailed clinical, epidemiological and demographic data were collected after obtaining written informed consent. ELISA testing tested the sera from blood samples for IgM antibodies against scrub typhus using a commercial kit (Scrub Typhus IgM ELISA by InBiOS International, Inc., USA). Samples were also tested for dengue, leptospira, malaria and typhoid.

Statistical analysis

The data generated in this study were subjected to statistical analysis using IBM SPSSv21.0 for windows. Categorical groups were associated with using chi square (χ2) test. P-value less than 0.05 were considered statistically significant.

Ethical statement

The Institutional Ethics Committee approved the study. (Approval No: IEC 31/17). Serum samples were collected after obtaining written informed consent from the patients.

  Results Top

Out of a total of 125 patients, 20% were found positive for scrub typhus [Figure 1].
Figure 1: Analysis of positive scrub typhus patients

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Demographic data

Among all participants, male and female ratio was 1.3:1, while among scrub typhus patients a ratio of 1.5:1 was found [Table 1]. The mean age of patients with scrub typhus was found to be 44.16±18.74 years. Seropositivity was found mostly in the age group of >50 years (40%), which was statistically not significant [Table 1]. Seropositivity was more from rural (22%) as compared to urban (18%) localities [Table 1]. Though we had patients from all 24 districts of central and eastern regions of Uttar Pradesh, scrub typhus positive cases were found only from 12 districts, with a maximum of eight cases from Lucknow, followed by three cases from Faizabad, two cases each from Barabanki, Sitapur, Sultanpur and Lakhimpur Kheri, and one case each from Basti, Gorakhpur, Deoria, Gonda, Pratapgarh and Sonebhadra. Statistically, significant seropositivity was found from Deoria, Lakhimpur Kheri, and Sonebhadra districts [Table 2], [Figure 2].
Table 1: Demographic analysis of patients

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Table 2: District wise distribution of patients

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Figure 2: Map of Uttar Pradesh, India showing district wise distribution of scrub typhus (Map in Uttar Pradesh large district in census 2011)

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Epidemiological data

All the positive cases were found during the monsoon and post-monsoon months (June to October), with a maximum seropositivity from the month of September (32.35%), followed by August (27.27%) and October (25.81%) [Figure 3]. Seropositivity was found to be statistically significant in the month of September. A history of rainfall was found to be more commonly associated with scrub typhus positive patients and this association was statistically significant. No clinical parameter was found to be statistically significant [Table 3].
Figure 3: Month-wise distribution of positive patients of scrub typus

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Table 3: Distribution of epidemiological and clinical data of patients

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Co-infection with other diseases

We observed coexistence of leptospirosis (40%), dengue (20%) and malaria (4%) with scrub typhus positive patients. No coexistence of typhoid with any scrub typhus positive patient was found in this study.

  Discussion Top

Around all areas of India is coming under tsutsugumushi triangle made for geographical distribution of scrub typhus[9] so central and eastern Uttar Pradesh is also included in it but seroprevalence of disease was reported in recent few studies from this region[6],[7],[8]. In this study, 20% of patients were found positive for scrub typhus. The reported prevalence was 3.49% from 1999–2004 and 16.05% during the period 2005–2009 from Delhi in a study conducted by Mittal V et al.[10] Bhargava et al. in 2014 reported a 11.2% prevalence from Uttarakhand and adjoining parts of Uttar Pradesh[7]. A prevalence of 22.8% was reported in a study from Rajasthan by Takhar RP et al. in 2017[11]. Among studies from Uttar Pradesh, a prevalence of 25.4% by Rizvi et al. from Aligarh was reported in 2018[12]. Tripathi et al reported in 2018 19.75% prevalence of scrub typhus from Uttar Pradesh[8]. Our study was also concord with these studies. Various studies reported existence of scrub typhus in Acute Encephalitis Syndrome (AES) outbreaks in Gorakhpur and Deoria districts among children presenting with an acute febrile illness during the post-monsoon season[13],[14],[15],[16].

After analyzing the prevalence data of scrub typhus from recent and older studies, it was observed that the prevalence has been increasing continuously for the last two decades[17]. This continuous rise can be due to re-emergence of the disease and/or increased awareness among clinicians. In some regions, in India, scrub typhus disappeared completely for some time. It has re-emerged in various regions in the 21st century after years of quiescence[18].

In our study, we found a maximum seropositivity in the older age group. Other studies also reported positivity in old age group[19],[20]. Cause of more positivity among higher age group of >50 years is not clearly known but it may be due to low immunity in this older age group and repeated exposure in their life time. Another study suggested that it was due to multivariate analysis, and absence of eschar. WBC counts > 10, 000/mm3, and albumin < 3.0 g/dL were found to be independently predictive variables for the occurrence of scrub typhus[21]. In maximum studies female were found positives than man[11],[19],[22] but in our study more positivity among males as compared to females was seen. Activities of male involves outdoors games, occupational exposure (animal handling, agriculture and fisheries) as well as recreational activities (hiking, camping, rafting and rock climbing) leading to more exposure to mites serve as an important reason for transmission of scrub typhus. Observation in our study is similar to few studies, who had reported more men than females were affected in their studies[23],[24],[25].

In our study ratio of rural and urban cases were approximately same (1.2:1). Most of the studies showed preponderance of positive cases in rural area due to existence of mite habitats predominantly in rural and periphery of urban areas. Small mammals including rodents also predominantly found in rural areas serving as vector for mites may also contribute to preponderance for rural population[26]. In our study urban cases increased due to urban construction, which is spreading with rampant pace, provides easy shelter for rodents that are carrier of scrub typhus. Urban concentrations in slums and hutments along the culverts/ pool waters bodies used both by animal and human are the most possible cause of higher infection in this population.

Majority of the cases of scrub typhus (96%) in our study were from monsoon and post monsoon months (July–October). This was similar to most of the previous studies[8],[22],[25],[26]. We included a history of rainfall as an important epidemiological determinant in our study, which was found to have a statistically significant association with scrub typhus positivity. The monsoon and post-monsoon season serve an important and favorable environmental condition for the multiplication of mites. Proliferation of shrubs and small mammals including rodents in this season serve as a habitat for mites. Preponderance of scrub typhus in the rural population, and seasonal changes were consistent with previous studies but rainfall as epidemiological criteria was not included in these studies[8],[22],[25],[26]

In our study cases were found in around 50% districts of Uttar Pradesh especially from eastern UP. It may be due to existence of favorable natural habitat for mites such as agricultural crops, shrubs and small mammals in these districts. Due to a lack of previous studies on the district-wise distribution of scrub typhus and the small sample size from each district in our study, other confounding factors responsible for the existence of scrub typhus in twelve districts and the nonexistence in the remaining districts cannot be ruled out. Cases were found in adjacent districts of Bihar may be due to similar environmental factors. A study of sAES from the various districts of Bihar revealed a scrub typhus seropositivity of 36.36% and 25% from Sivan and Gopalganj districts respectively, further strengthening the existence of scrub typhus in the districts of Uttar Pradesh adjacent to Bihar[27].

Among the clinical data, generalized symptoms of fever >39°C, headache, and myalgia were found in all the positive cases. We could not find an eschar in any of the patients. An eschar at the site of chigger bite is highly suggestive of scrub typhus but is reported to occur in a variable proportion of patients[6]. Eschars were also not found in any patients in the studies from Aligarh, Uttar Pradesh, and Rajastan[12],[28].

In our study coexistence of scrub typhus with dengue, leptospirosis and malaria were found. This was also reported in other studies [29],[30]. Further, the presence of other disease like leptospirosis, dengue and malaria with scrub typhus, in our study can be interpreted as coexistence or cross reactivity. This should be confirmed by more sensitive and specific methods like PCR. Certainly, there are limitations in our study. Study has small sample size and not able to collect convalescent sample due to cost of the testing kit, as the study did not receive external funding. As this is a hospital-based study and limited to a small area of eastern and central UP, the results cannot be applied to the whole population.

  Conclusion Top

Scrub typhus is found to be an important cause of acute febrile illness. It is necessary to include it in differential diagnosis of AFI cases even in absence of eschar. Diagnostic facilities of this as a screening testing by RCT should be started in primary care center or community health center of rural areas of districts of central and eastern UP.

Conflict of interest: None

  References Top

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  [Figure 1], [Figure 2], [Figure 3]

  [Table 1], [Table 2], [Table 3]


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