Detection of Immunoglobulin M and Immunoglobulin G Antibodies Against Orientia tsutsugamushi for Scrub Typhus Diagnosis and Serosurvey in Endemic Regions

Predictors of encephalitis in children with scrub typhus-associated acute febrile illness

Scrub typhus (ST) is an emerging public health concern in India. Despite being treatable, 20-30 % of acute febrile illnesses (AFI) progress to encephalitis in endemic regions. This study aimed to identify early markers for encephalitis development in children hospitalized with AFI and positive Orientia tsutsugamushi (Ots) serology. This prospective cohort study was conducted during January-December 2018, involved AFI patients (age ≤ 16 years) tested positive for IgM antibodies against Ots. These patients were followed up prospectively to monitor the development of encephalitis. The clinical and biochemical data from ST-AFI cases developed encephalitis were compared with ST-AFI cases did not develop encephalitis. Univariate and multivariate logistic regression analysis were used to determine predictors of encephalitis. Total 41 out of 190 (21.6 %) ST-AFI patients progressed to encephalitis. The multivariate regression analysis identified initiation of antibiotic therapy after more than 5 days from illness onset (OR 4; 95 % CI [1.4-11.6]), vomiting (>3 episodes) (OR: 10.9; 95 % CI [2.3-51.4]), Glasgow Coma Scale (9-12) (OR 6; 95 %CI [1.9-19]), calcium level (≤8 mg/dL) (OR 6.1 95 % CI [1.1-32.6]), serum creatinine (>1 mg/dL) (OR 16.8, 95 % CI [1.5-191.9]), and oxygen support requirement (OR 19.5, 95 % CI[6.4-59.3]) at admission as predictor of encephalitis in ST-AFI cases. The sensitivity and specificity of model was 67.50 % and 93.96 % respectively, Hosmer-Lemeshow test (χ2 = 8.82, P = 0.3584), and an area under the ROC curve of 0.9514. Study found initiation of antibiotic more than 5 days after illness onset, multiple vomiting episodes, low GCS, hypocalcaemia, high creatinine, and oxygen need as predictors of encephalitis in ST-AFI patients.

Association of Scrub Typhus in Children with Acute Encephalitis Syndrome and Meningoencephalitis, Southern India

Scrub typhus is an established cause of acute encephalitis syndrome (AES) in northern states of India. We systematically investigated 376 children with AES in southern India, using a stepwise diagnostic strategy for the causative agent of scrub typhus, Orientia tsutsugamushi, including IgM and PCR testing of blood and cerebrospinal fluid (CSF) to grade its association with AES. We diagnosed scrub typhus in 87 (23%) children; of those, association with AES was confirmed in 16 (18%) cases, probable in 55 (63%), and possible in 16 (18%). IgM detection in CSF had a sensitivity of 93% and specificity of 82% compared with PCR. Our findings suggest scrub typhus as an emerging common treatable cause of AES in children in southern India and highlight the importance of routine testing for scrub typhus in diagnostic algorithms. Our results also suggest the potential promise of IgM screening of CSF for diagnosis of AES resulting from scrub typhus.

Genotypic Characterization of Orientia tsutsugamushi Isolated From Acute Encephalitis Syndrome and Acute Febrile Illness Cases in the Gorakhpur Area, Uttar Pradesh, India

Scrub typhus infections caused by Orientiatsutsugamushi (OT), continue to remain underdiagnosed globally, due to the lack of distinctive symptoms. The elusive nature of the Acute Encephalitis Syndrome (AES) outbreak in Gorakhpur, Uttar Pradesh that claimed numerous pediatric lives was the driving force of this study which involved serological diagnosis (IgM-ELISA), isolation of OT in cell culture, confirmation by PCR, and characterization by Sanger sequencing. In total, 12 out of 36 patients were seropositive, of which 4 were positive by PCR. Upon enrichment in cell culture, additional 3 patients (including two seronegative) were detected positive by PCR. In total, three of these 7 patients were found to be infected with two strains of OT. Taken together, this study for the first time reports the occurrence of dual infections in addition to three circulating OT genotypes (Gilliam, Kato, and Karp-like) and highlights the significance of enriching OT in cell culture systems for efficient molecular detection.