Rapid Serologic and Molecular Diagnosis of Scrub Typhus among Suspected Febrile Patients Visiting Mymensingh Medical College Hospital.

Scrub typhus, caused by the bacterium- Orientia tsutsugamushi is one of the leading causes of undifferentiated treatable febrile illness in Asia pacific region. It is grossly under diagnosed in many tropical countries of South Asia including Bangladesh, due to wide range of non-specific clinical presentations, low index of suspicion among clinicians, limited awareness and lack of accurate diagnostic facilities. This cross-sectional descriptive study was conducted at Department of Microbiology, Mymensingh Medical College to diagnose scrub typhus by rapid Immunochromatographic test (ICT) as well as molecular detection of O. tsutsugamushi by Nested PCR and automated nucleotide sequencing among suspected febrile patients in Mymensingh, Bangladesh during 2019-20. Blood samples were collected from 402 febrile patients of suspected Rickettsial illness, referred from inpatient and outpatient departments of Medicine and Pediatrics, Mymensingh Medical College Hospital (MMCH). Among the enrolled 402 patients, 89 samples (22.13%) were seropositive by Immunochromatographic test (ICT) and 65 samples (16.16%) were positive for O. tsutsugamushi DNA by Nested PCR, targeting 47KDa gene. Therefore, 113/402 (28.10%) samples were positive for scrub typhus by PCR and/ or ICT. Highest number of patients was detected positive by nested PCR during the first 5-10 days of fever but only 2 cases were positive after 20 days. In case of ICT, highest positivity for only IgM (8.13%) and both antibodies (2.43%) were documented in first 5-10 days of fever, but IgG positivity was highest (41.66) in >20 days of fever. From 65 PCR positive samples, automated nucleotide sequencing was performed on 20 randomly selected samples and all were genetically confirmed to be O. tsutsugamushi.