There were 48 STM, 44 ABM and 31 TBM cases during the study period. In those with STM, 23 were positive by Weil Felix test, 15 by Scrub IgM ELISA and 10 were positive by both. Eleven (22.9%) of the patients with STM had eschar. Of those with bacterial meningitis, the causative organisms were Streptococcus pneumoniae in 22 (50%), Hemophilus influenzae in 11 (25%), non-typhoidal Salmonella in 3 (6.8%), Enterococcus spp. and Neisseria meningitides in 2 (4.5%) each, and S. agalactiae, S. pyogenes, Burkholderia pseudomalleii and Acinetobacter baumannii in one each. Definite tuberculous meningitis was diagnosed in 13 (41.9%) and probable tuberculous meningitis in 18 (58.1%).

Comparative data on the demographic, clinical, investigations and outcome parameters is shown in Table I. Children with STM were considerably older (mean 9.12 years) than ABM (mean 3.1 years) or TBM (mean 6.36 years). Most children (83.3%) with STM presented with 4-10 days of fever, while children with ABM presented earlier (50% within 3 days of fever) and children with TBM later (80.7% over 10 days of fever). Splenomegaly was more common with STM, and hepatomegaly with ABM and TBM. Among the blood investigations, thrombocytopenia showed a strong association with scrub typhus.

TABLE I Demographic, Clinical and Outcome Parameters in Children With Three Types of Meningitis (N=123)

STM had a significantly shorter hospital stay and better outcome (less death/premature discharge likely to have caused death and neurological deficits). Children with scrub typhus were treated with doxycycline alone in 18 (37.5%), azithromycin alone in 3 (6.3%), chloram-phenicol alone in 3 (6.3%), doxycycline and azithromycin in 20 (41.7%), doxycycline and chloramphenicol in 2 (4.2%), azithromycin and chloramphenicol in 1 (2.1%) and doxycycline, azithromycin and chloramphenicol in 1 (2.1%).

Important differences in clinical features (age of presentation, duration of fever and presence of liver or spleen enlargement) between the three types (STM, ABM, and TBM) were observed in this study.

The association between older children and scrub typhus meningitis is similar to that reported by Bhat, et al. (mean age of 8 years) [5]. Bacterial meningitis and tuberculous meningitis have been reported in much younger children with median ages of 6 months and 32 months, respectively [9,10]. Fever duration of 4-10 days was significantly more likely with STM in this study. Bhat, et al.[5] and Varghese, et al. [11] reported a mean fever duration of 7.9 days in children and 8.4 days in adults with STM, respectively. Fever and non-specific symptoms are reported to precede CNS manifestations in childhood tuberculosis meningitis by 13-42 days [12] Splenic enlargement in over half of those with STM is consistent with reported literature [5].

Among the blood counts, only thrombocytopenia was significantly associated with scrub typhus meningitis, similar to reports in adults [11]. CSF parameters for STM were comparable to previous reports except for CSF glucose that was considerably lower in our study (39 mg/dL vs 64.2 mg/dL) [5]. Children with STM had signi-ficantly less hospital stay, and no neurological sequelae or death. Bhat, et al. [5] too reported considerably less mortality with STM compared to scrub typhus without meningitis [5]. This is in contrast with the 25% mortality that has been reported in adults with STM [11]. Eschar, a valuable clue to scrub typhus [13] was present in 23% of our patients, which is similar to reported literature [4,5]. Careful examination of the hidden skin folds of the axillae, groin and genitalia is important. [14].

Our study has a number of limitations such as the retrospective nature of the analysis, the convenience sample used, the reliance on serological tests for diagnosis of scrub typhus, and the reliance on blood serology rather than a CSF-based test for diagnosis of STM. However, with good specificity being reported with these tests, over-diagnosis of STM is unlikely.

In conclusion, scrub typhus meningitis is an important cause of acute and sub-acute meningitis. In any child of older arrange group with meningitis with a sub-acute presentation, presence of splenic enlargement and thrombocytopenia should alert the clinician to the possibility of scrub typhus. Finding an eschar is a valuable clue to diagnosis of scrub typhus. Appropriate specific testing for scrub typhus and specific antibiotic therapy results in good prognosis.

Acknowledgements: Mr E Prabhu who helped with data collection and data entry.

Contributors:SRK: data collection, design of study, preparation of the manuscript; AC, VPV: data interpretation, preparation of manuscript; PS: data analysis and preparation of manuscript; WR: conception and design of study, data analysis and preparation of the manuscript. All authors approved the final manuscript.

Funding: None; Competing interests: None stated.

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