|BRIEF RESEARCH ARTICLE
|Year : 2014 | Volume
| Issue : 4 | Page : 281-283
Scrub typhus-an emerging entity: A study from a tertiary care hospital in North India
Aroma Oberoi, Shereen Rachel Varghese
Department of Microbiology, Christian Medical College and Hospital, Ludhiana, Punjab, India
|Date of Web Publication||5-Dec-2014|
Department of Microbiology, Christian Medical College and Hospital, Ludhiana - 141 008, Punjab
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Scrub typhus is a tropical febrile zoonotic disease caused by Orientia tsutsugamushi of the rickettsial family. These are obligate; intracellular Gram-negative coccobacilli transmitted by the bite of infected mites. It is usually under-diagnosed in India due to its varied and nonspecific clinical presentation, limited awareness, and low index of suspicion among clinicians and lack of diagnostic facilities. This study was planned to monitor the level of scrub typhus-specific antibodies among febrile patients in a tertiary care hospital over a period of 1 year for which a rapid qualitative immunochromatographic assay (Standard Diagnostics, Korea) was introduced for the detection of IgM, IgG and IgA antibodies to O. tsutsugamushi from the serum of suspected febrile patients. A total of 98 out of 772 fever patients (12.69%) tested positive for the presence of antibodies against O. tsutsugamushi. Persistent high-grade fever was the defining characteristic in all the cases with the presence of an eschar in only 10.2% (10/98) of cases. Three patients died during the study period while the rest responded to treatment with doxycycline.
Keywords: Eschar, Scrub typhus, Orientia tsutsugamushi
|How to cite this article:|
Oberoi A, Varghese SR. Scrub typhus-an emerging entity: A study from a tertiary care hospital in North India. Indian J Public Health 2014;58:281-3
|How to cite this URL:|
Oberoi A, Varghese SR. Scrub typhus-an emerging entity: A study from a tertiary care hospital in North India. Indian J Public Health [serial online] 2014 [cited 2020 Aug 11];58:281-3. Available from: http://www.ijph.in/text.asp?2014/58/4/281/146299
Scrub typhus is increasingly implicated as an important cause of acute undifferentiated febrile illness in several parts India.  Orientia tsutsugamushi, the etiological agent of scrub typhus is an obligate intracellular Gram-negative coccobacilli belonging to the family rickettsiae., The larvae of trombiculid mites are the implicated vector and reservoir of the bacteria and can efficiently transmit it to their offspring transovarially. 
Scrub typhus is an important cause of acute febrile illness and needs to be differentiated from other causes of febrile illnesses such as malaria, enteric fever, dengue, leptospirosis, infectious mononucleosis etc.  This disease is also significant as any undue delay in diagnosis and initiation in appropriate therapy can often result in severe complications such as acute respiratory distress syndrome, septic shock and multisystem organ failure often culminating in death in morbid patients. Acute kidney failure associated with scrub typhus has also been reported in the tropics. 
Observing the increase in the number of undifferentiated febrile illness in our hospital along with persistent clinicians demand, a serological test for the detection of scrub typhus antibodies was introduced in our laboratory in October 2011. Here we present the scrub typhus scenario in our tertiary care hospital in 1 year.
Our aim was to study the magnitude of scrub typhus antibodies among febrile patients in a tertiary care hospital and to assess clinical features and outcomes of serologically positive patients.
Serum samples from suspected febrile patients were tested for the presence of IgM, IgG and IgA antibodies against O. tsutsugamushi using the Standard Diagnostics (SD) Bioline Tsutsugamushi solid phase immunochromatographic assay (SD, Korea). This is a rapid qualitative test which can be used as a preliminary diagnostic tool for the detection of scrub typhus-specific antibodies in human serum, plasma or whole blood. The test has a sensitivity of 99%, specificity of 96% and serological agreement of 97.5% with immunofluorescent assay.  This test uses the major surface protein 56 kDa type-specific antigen of O. tsutsugamushi isolates. Retrospectively, the clinical findings of the serologically positive patients were also studied. Other routine febrile parameters such as blood culture, malaria and tests for leptospirosis were also done to ascertain other causes of pyrexia.
During the 1-year study period, a total of 772 serum samples were received in the Department of Microbiology for the detection of O. tsutsugamushi specific antibodies. Of these, 98 samples (12.69%) tested positive for the presence of antibodies against O. tsutsugamushi. The number of adult male and female positive patients were 13.6% (60/441) and 12.05% (37/307) respectively. Twenty-four samples were tested from pediatric patients of which only 1 was positive. The month-wise distribution of serologically positive cases is depicted in [Table 1]. A retrospective analysis of the clinical presentation of the serology positive patients found that a prolonged fever with a mean duration of 14.71 days was the predominant symptom. The presence of an eschar, though characteristic of scrub typhus was detectable in only 10.2% of patients. Other clinical findings included hepatosplenomegaly and lymph node enlargement. Thirty-one patients (31.6%) had complications such as acute respiratory distress syndrome, hypotension, acute kidney injury and neurological manifestations such as headache, loss of sensorium and seizures with meningeal signs in varying combinations. Twenty patients (20.4%) had other comorbidities such as tuberculosis, hepatitis, malaria, dengue and enteric fever. During the course of the study, three patients expired due to cardiac arrest and one patient left against medical advice. All the other serologically positive patients were treated with doxycycline and showed remarkable improvement.
Scrub typhus as an entity is not rare in the tropics and should be suspected in patients from endemic areas with a high risk of environmental exposure and who develop high grade fever with or without other symptoms.  The proportion of scrub typhus cases was 13% as seen in our study, which compares well with other studies from India.  Persistent high grade fever was the predominant feature in our study though the presence of an eschar was not observed in all cases. Studies from South India reported the presence of a rash in 22% of cases, whereas Chrispal et al. reported a 45.5% prevalence of eschar in their study. , Mathai et al.  also reported an increase in scrub typhus cases during the cooler months and this phenomenon was also observed in our study where maximum positivity was observed in the months following the monsoon leading to winter. The disease also has a predilection for the cooler months which coincides with an increase in shrub vegetation that in turn favors the growth of the vector and the same has been reported in international studies also. 
|Table 1: Month-wise prevalence and positivity rates for a period of 1-year|
Click here to view
Patient outcomes in our study were favorable with patients responding to the treatment regimen of doxycycline. A Cochrane review on antibiotics for scrub typhus has documented the effectiveness of doxycycline and tetracycline to treat the disease. However, rifampicin has been found to be more effective than doxycycline in areas where scrub typhus appears to respond poorly to standard antirickettsial drugs. 
The serological test for the preliminary identification of scrub typhus-specific antibodies was found to be rapid and easy to perform along with a high sensitivity and specificity and hence it has proved to be a good indicator of the presence of antibodies that are reactive to the type-specific antigen of O. tsutsugamushi in patients suffering from undifferentiated febrile illnesses. Furthermore, the fact that there is a dramatic therapeutic response to a cheap and readily available drug validates the importance of the need to suspect this disease in patients suffering from prolonged fever in the absence of any other significant diagnosis.
In recent years, a number of studies have been published recording the re-emergence of scrub typhus in parts of North and North-East India. ,, Most of these are however, hospital-based studies, which have their own limitations but since there is a paucity of community-based data, clearly more research on this entity is required with respect to epidemiology, pathogenesis, clinical findings and diagnosis, especially in the context of the Indian subcontinent. With increased awareness, surveillance, prophylaxis, early diagnosis and appropriate treatment we can prevent morbidity and mortality due to this undiagnosed entity.
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