Scrub typhus: an unrecognized threat in South India – clinical profile and predictors of mortality

Abstract

Summary Scrub typhus is an important cause of acute undifferentiated febrile illnesses in the Indian subcontinent. Delay in diagnosis and in the initiation of appropriate treatment can result in severe complications such as acute respiratory distress syndrome (ARDS), septic shock and multisystem organ failure culminating in death. We conducted a prospective, observational study to delineate the clinical profile and predictors of mortality in scrub typhus in adults admitted to the medical wards of a tertiary care, referral hospital in South India over a one-year period. The case fatality rate in this study was 12.2%. Metabolic acidosis (odds ratio [OR] 6.1), ARDS (OR 3.6), altered sensorium (OR 3.6) and shock (OR 3.1) were independent predictors of mortality. It appears that scrub typhus has four possible overlapping clinical presentations: mild disease; respiratory predominant disease; central nervous system predominant disease (meningoencephalitis); or sepsis syndrome. Given the telltale presence of an eschar (evident in 45.5%), the characteristic clinical profile and the dramatic therapeutic response to a cheap, yet effective, drug such as doxycycline, medical practitioners in the region should have ample opportunity to reach an early diagnosis and initiate treatment which could, potentially, reduce the mortality and morbidity associated with scrub typhus.

Does the presence of an eschar correlate with severity of scrub typhus infection?

“…Previous studies from India show an incidence of acute respiratory distress syndrome of 8-25% with majority of them requiring invasive ventilation. [7,12,13] Tsay and Chang reported no association between the presence of an eschar and pulmonary involvement. [13] In our study 8.2% of patients overall required invasive ventilation with no difference noticed between the two groups.…”

“…[3,4] It is a clinically important disease because it is associated with many serious complications and has a mortality rate of 14-20%. [5][6][7] Its incidence in certain parts of India reaches endemic proportions and accounts for up to 50% of undifferentiated febrile illness in those areas during cooler months of the year. [3,7] The clinical finding of a pathognomonic eschar in a patient with febrile illness is the most important clue to the diagnosis of ST.…”

“…[5][6][7] Its incidence in certain parts of India reaches endemic proportions and accounts for up to 50% of undifferentiated febrile illness in those areas during cooler months of the year. [3,7] The clinical finding of a pathognomonic eschar in a patient with febrile illness is the most important clue to the diagnosis of ST. The eschar usually forms 7 days after inoculation, and is usually not noticed by the patients however, as the chigger bite is painless.…”

“…CNS involvement is often a prominent clinical manifestation of ST infection and aseptic meningitis occurs in 12.5-26% of affected patients. [7,14,15] Some studies have shown altered sensorium to be an independent platelet count<100,000/cells cu mm), leucopenia (total WBC count<2500/cells cu mm), leucocytosis (total WBC count>11,000/cells cu cc) or evidence of coagulopathy; Renal involvement: Serum creatinine>2 mg/dL or need for dialysis; CVS involvement: Hypotension or need for inotropic or vasopressor support; CNS involvement: Alteration in the level of consciousness or aseptic meningitis; Hepatic involvement: Serum bilirubin>2 mg/dL or three fold elevation of SGOT/SGPT or elevated ALP; GI involvement: GI bleed; Respiratory involvement: PaO2/FiO2 ratio<300 or need for ventilator assistance. OR=Odds ratio, CI=Confidence interval, WBC=White blood cell, CVS=Cardiovascular system, CNS=Central nervous system, SGOT=Serum glutamic oxaloacetic transaminase, SGPT=Serum glutamic-pyruvate transaminase, ALP=Alkaline phosphatase, GI=Gastrointestinal, RS=Respiratory system predictor of mortality.…”

Evaluation of two diagnostic methods of scrub typhus with Bayes rule

“…The main difficulty in the diagnosis and management of rickettsia infection is the lack of facilities for definitive diagnosis. 2 Nowadays, the Weil-Felix test is considered obsolete, but the better diagnostic technique enzyme-linked immunosorbent assay (ELISA) is the indirect fluorescent antibody (IFA) assay is available at referral centers.3Additional complications, gastrointestinal manifestations, tinnitus and hepatitis syndromes from rickettsial infections have reported from Asian countries. 4 In India, the diagnosis of rickettsia infections is not dependable due to the lack of community-based data and non-availability of impeccable laboratory tests.…”