|Year : 2021 | Volume
| Issue : 6 | Page : 268-269
Scrub typhus - Suspect early, act fast
AR Mullai Baalaaji
Kovai Medical Center and Hospital; Department of Pediatrics, Kovai Medical Center and Hospital Institute of Health Sciences and Research, Coimbatore, Tamil Nadu, India
|Date of Submission||18-Oct-2021|
|Date of Acceptance||25-Oct-2021|
|Date of Web Publication||19-Nov-2021|
Dr. A R Mullai Baalaaji
Pediatric Intensive Care Unit, Kovai Medical Center and Hospital, Coimbatore, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Mullai Baalaaji A R. Scrub typhus - Suspect early, act fast. J Pediatr Crit Care 2021;8:268-9
Scrub typhus is an arthropod-borne acute febrile illness resulting from bite of the larval form of trombiculid mite (chigger). The etiological agent, Orientia tsutsugamushi, is an obligate intracellular bacterium that targets endothelial cells and phagocytes for replication. Accordingly, the disease pathogenesis manifests predominantly in highly vascularized organs such as lung, liver, and brain. The illness can vary from mild, undifferentiated fever to severe life-threatening illness complicated by myocarditis, septic shock, meningoencephalitis, interstitial pneumonitis, acute respiratory distress syndrome (ARDS).
Scrub typhus has been endemic in the Asia-Pacific region, bounded by Pakistan in the west, Japan in the east, Russia in the north, and Australia in the south, termed traditionally as the Tsutsugamushi triangle. The distribution is found to be emerging outside the endemic triangle with increasing reports of potential and confirmed cases and regional outbreaks. Ecological, climate, host, and human pattern changes could be the reason for this shift in geographical distribution. In addition, recently identified Orientia species – Candidatus Orientia chuto and others have expanded the etiological spectrum of the disease as well.
Neurological involvement in Scrub typhus is well known and is reported from 11% to 41% in published literature. The manifestations are protean and range from aseptic meningitis to meningoencephalitis, isolated cranial nerve palsies, polyradiculopathy, demyelination, infarcts. The manifestations occur due to direct as well as immune-mediated processes. Being an intracellular pathogen, there is an invasion of vascular endothelium and widespread vasculitis which explains many of the disease manifestations. Furthermore, direct entry into the central nervous system (CNS) has been noted with varied CNS pathologies such as focal mononuclear cell infiltration of the leptomeninges, perivasculitis, microglial activation, and brain hemorrhage.
Acute encephalitis is a serious manifestation of Scrub typhus, and prompt initiation of appropriate therapy along with supportive care is very crucial for favorable outcomes. In the past, acute encephalitis syndrome outbreaks were centered around Japanese encephalitis, but the trends are now changing with increasing reports of dengue and Scrub typhus as important causative agents. It is important to suspect Scrub typhus as a differential at the outset of presentation, as there is a definitive treatment available and the prognosis is excellent when treated early, with improved survival without morbidity.
In this current issue of the Journal of Pediatric Critical Care, Parida et al. have enumerated the clinical profile and outcome of children with scrub typhus meningoencephalitis (STME) admitted to a tertiary care center in Eastern India. Among children with Scrub typhus, 12.4% had features of meningoencephalitis. Other salient findings in addition to neurological manifestations were fever, hepatosplenomegaly, leukocytosis, elevated CRP, transaminitis. CSF analysis revealed lymphocytic pleocytosis with elevated protein and was abnormal in all children with neurological manifestations. Curiously, thrombocytopenia and renal involvement were not observed in any of the study participants, and only one patient had ARDS. All children diagnosed with STME received doxycycline for 7–10 days, as oral or injectable, depending on the severity. Pediatric intensive care admission was needed in 12 out of 27 cases, and all patients recovered with gradual improvement of neurological manifestations. Due to small numbers, comparison between meningoencephalitis due to scrub typhus and other etiologic agents could not be made, however, there were 6 deaths among 29 children with encephalitis due to other etiologies. The details of neurological status at discharge are not available for comparison. Overall, the study reiterates the fact that encephalitis is a common manifestation in children with scrub typhus and overall outcomes are favorable with appropriate treatment.
Diagnosis of scrub typhus in most circumstances is through indirect method, relying on detection of antibodies against O. tsutsugamushi through Weil–Felix agglutination method, immunofluorescence assays, enzyme-linked immunosorbent assay (IgG and IgM), however, they detect antibodies 5–10 days after infection onset. Direct methods such as bacterial isolation require a high-contaminant biosafety level 3 facility and are not feasible in most circumstances. Polymerase chain reaction-based diagnostics are highly specific and sensitive and can detect infection even in early stages, however, their widespread applicability is constrained by the expense and sophisticated instrument facility. Hence, it becomes imperative that empirical treatment for Scrub typhus should be initiated at appropriate clinical circumstances in endemic regions and while facing outbreaks, while awaiting confirmation based on the available diagnostic methods.
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