|Year : 2022 | Volume
| Issue : 3 | Page : 75-76
Scrub typhus in infants: Food for thought
A R Mullai Baalaaji
Department of Pediatric Critical Care, Kovai Medical Center and Hospital, Coimbatore, Tamil Nadu, India
|Date of Submission||13-Mar-2022|
|Date of Acceptance||29-Mar-2022|
|Date of Web Publication||12-May-2022|
Dr. A R Mullai Baalaaji
Department of Pediatric Critical Care, Kovai Medical Center and Hospital, Coimbatore, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Baalaaji A R. Scrub typhus in infants: Food for thought. J Pediatr Crit Care 2022;9:75-6
Scrub typhus, an emerging rickettsial infection, causes a wide spectrum of clinical manifestations ranging from undifferentiated fever to severe illness, resulting in multiorgan failure and eventual mortality in untreated cases. The causative agent Orientia tsutsugamushi is an obligate intracellular bacterium, which has unique biological characteristics such as expression of atypical peptidoglycans and lack of lipopolysaccharides, unlike other Gram-negative bacteria. The protean manifestations of the disease can be explained by the underlying pathophysiology characterized by widespread endothelial injury.
Clinical features of scrub typhus have been well characterized by various case series and cohort studies across India. It is prudent to suspect scrub typhus as an important differential in the setting of any undifferentiated fever or fever with organ failures in any child. However, infants are a special group of population, where a diagnosis of scrub typhus may be less recognized or suspected, due to the environmental restrictions. Nevertheless, infants can get exposed to the causative chigger bite through the family members who may carry home the chiggers from outside. It is also be possible that the chigger movement to a safer indoor place during monsoons could put them at risk of getting infected despite remaining indoors.
Infants with scrub typhus tend to have a more severe manifestation with hepatic, pulmonary, hematologic involvements and requiring intensive care treatment in a majority. The reason for sicker presentation could be due to inherent immune mechanisms which are yet to be fully understood or simply a reflection of delayed recognition of the illness where bacterial sepsis, other tropical infections, and noninfectious conditions are thought about as the possible differentials.
In the current study, severe manifestations were more commonly observed in infants' age group, and the incidence of multiorgan dysfunction syndrome (MODS) was higher in children aged <1 year. It is to be noted that the mean duration of fever was higher in infants (9.2 ± 3.2 vs. 5.6 ± 2.5 days, P = 0.04) compared to older children, reiterating the fact that the diagnosis was not suspected in them earlier. That could well explain some of the consistent observations that infants tend to have a more severe manifestation of scrub typhus.
Hyperferritinemia, defined as ferritin levels more than 500 μg/L, is commonly observed in tropical infections such as dengue and scrub typhus; however, the real diagnostic and prognostic significance of the same needs to be well elucidated with more scientific studies. In a secondary analysis study from North India, the authors concluded that hyperferritinemia is a common observation in children with scrub typhus, seen in 72.6% of children; however, it did not predict survival. Organ dysfunction and risk scores PRISM III and PELOD 2 at admission were better predictors of mortality. More data are needed to understand the pathogenesis and role of these biomarkers.
A few of the infants in the current cohort required immunomodulator treatment in addition to specific antimicrobial therapy. Various immunomodulatory therapies such as steroids, intravenous immunoglobulin, anakinra, and plasmapheresis have been employed historically to target the immune dysregulation arm in addition to specific appropriate antimicrobial therapy targeting the infection in children with hyperferritinemic sepsis-related MODS. Whether a similar approach is also beneficial when managing tropical infections such as scrub typhus is something that requires introspection. The bottomline, however, remains that early diagnosis and appropriate antimicrobial therapy will still be the most effective approach, reserving the use of other adjuvants to sicker ones who respond poorly to antimicrobials alone. The timeline of initiation of immunomodulators, choice of therapies, and biomarkers to guide the need for such therapies continue to remain food for thought.
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