Diagnostic Accuracy Assessment of Immunochromatographic Tests for the Rapid Detection of Antibodies Against Orientia tsutsugamushi Using Paired Acute and Convalescent Specimens

The diagnosis and treatment of scrub typhus should be emphasized in non-endemic areas: A retrospective case series study

The morbidity of tsutsugamushi is increasing and is no longer limited to endemic areas. Delayed diagnosis and inappropriate treatment can cause severe complications and increase mortality rates. We conducted a retrospective case series of patients with scrub typhus at our institution to report our experience and discuss the diagnostic modalities. We encountered 21 cases of scrub typhus at our institution between 2014 and 2022. The average age of the patients was 52 years (range: 22-63 years), 11 (52%) were farmers, and 11 (52%) had clear outdoor activities. Twenty (95%) patients had an ineffective history of general antibiotic treatment. The classic presentation was repeated fever in 95% of patients. Seventeen patients (81%) had eschar mainly on the groin (35%) and armpit (35%). Common laboratory findings included eosinophilia (95%), elevated alanine aminotransferase (95%), elevated aspartate aminotransferase (86%), thrombocytopenia (76%), lower hemoglobin (71%), and neutrophilia (38%). Six (29%) patients received the treatment of tigecycline, 4 (19%) patients received the treatment of doxycycline, and 11 (52%) patients received the treatment of minocycline. After 3 days of specific treatment, the eosinophilic levels showed a recovery trend. Twenty (95%) patients fully recovered, and 1 (5%) died. Careful physical examination and medical history are important for the early diagnosis of scrub typhus; clinicians in non-endemic areas need to strengthen their understanding of scrub typhus.

Serological Evidence of Scrub Typhus in Mizoram, North Eastern Region of India

Objective

Differentiating scrub typhus from other acute febrile illnesses is difficult due to non-specificity of clinical symptoms and relative absence of eschar in Indian population. Antibody based serological tests are mainstay of scrub typhus diagnosis. To order to determine the performance of immunochromatography and IgM ELISA, immunochromatography and scrub typhus IgM ELISA were performed to detect the presence of antibodies against Orientia tsutsugamushi in acute serum of patients with acute febrile illness.

Materials and Methods

A cross-sectional study was carried out in the Department of Microbiology, Civil Hospital Aizawl and Department of Microbiology, Civil Hospital Lunglei, Mizoram over a period of one year from October 1, 2018 to September 31, 2019. Serum samples from patients with acute febrile illness were processed for the detection of scrub typhus. A total of 253 samples were subjected to immunochromatography and IgM ELISA.

Results

Using scrub typhus IgM ELISA as gold standard, the sensitivity, specificity and negative predictive value were calculated. Of the 253 serum samples tested, 36 were positive by both scrub typhus rapid test and IgM ELISA. 27 samples which were negative by scrub typhus rapid test reacted positive by IgM ELISA. 66 samples which were positive by scrub typhus rapid test were negative by IgM ELISA.

Conclusion

Owing to the limitations of scrub typhus rapid test and immunfluorescence assay (IFA), commercially available recombinant IgM ELISA which has a good sensitivity and specificity may be an alternative in laboratories with moderate set up.

Genotypic Heterogeneity of Orientia tsutsugamushi in Scrub Typhus Patients and Thrombocytopenia Syndrome Co-infection, Myanmar

Serologic and molecular surveillance of serum collected from 152 suspected scrub typhus patients in Myanmar revealed Orientia tsutsugamushi of genotypic heterogeneity. In addition, potential co-infection with severe fever with thrombocytopenia syndrome virus was observed in 5 (3.3%) patients. Both scrub typhus and severe fever with thrombocytopenia syndrome are endemic in Myanmar.

Quantitative Serodiagnosis of Scrub Typhus Using Surface-Enhanced Raman Scattering-Based Lateral Flow Assay Platforms

A surface-enhanced Raman scattering-based lateral flow assay (SERS-LFA) technique has been developed for the rapid and accurate diagnosis of scrub typhus. Lateral flow kits for the detection of O. tsutsugamushi IgG (scrub typhus biomarker) were fabricated, and the calibration curve for various standard clinical sera concentrations were obtained by Raman measurements. The clinical sera titer values were determined by fitting the Raman data to the calibration curve. To assess the clinical feasibility of the proposed method, SERS-LFA assays were performed on 40 clinical samples. The results showed good agreement with those of the standard indirect immunofluorescence assay (IFA) method. SERS-LFA has many advantages over IFA including the less sample volume, simpler assay steps, shorter assay time, more systematic quantitative analysis, and longer assay lifetime. As SERS strips can be easily integrated with a miniaturized Raman spectrophotometer, field serodiagnosis is also more feasible.

Clinical and Epidemiological Patterns of Scrub Typhus, an Emerging Disease in Bhutan

Scrub typhus (ST) is a vector-borne rickettsial infection causing acute febrile illness. The re-emergence of ST in the Asia-Pacific region represents a serious public health threat. ST was first detected in Bhutan in 2008. However, the disease is likely to be under-diagnosed and under-reported, and the true impact is difficult to estimate. At the end of 2014, the SD Bioline Tsutsugamushi Test^TM rapid diagnostic test (RDT) kits became available in all hospitals to assist clinicians in diagnosing ST. We conducted a retrospective descriptive study, reviewing records from all hospitals of Bhutan to identify all RDT-positive clinical cases of ST in Bhutan in 2015. The aim was to evaluate the burden of ST in Bhutan, describe the demographic, spatial and temporal patterns of disease, and identify the typical clinical presentations. The annual incidence of RDT-positive cases of ST reporting to Bhutanese hospitals in 2015 was estimated to be 62 per 100,000 population at risk. The incidence of disease was highest in the southern districts with a subtropical climate and a high level of agricultural production. The highest proportion of cases (87%) was rural residents, with farmers being the main occupational category. The disease was strongly seasonal, with 97% of cases occurring between June and November, coinciding with the monsoon and agricultural production seasons. Common ST symptoms were not specific, and an eschar was noted by clinicians in only 7.4% of cases, which is likely to contribute to an under-diagnosis of ST. ST represents an important and neglected burden, especially in rural communities in Bhutan. The outcomes of this study will inform public health measures such as timely-awareness programmes for clinicians and the public in high-risk areas, to improve the diagnosis, treatment and clinical outcomes of this disease.

Scrub typhus point-of-care testing: A systematic review and meta-analysis

BACKGROUND

Diagnosing scrub typhus clinically is difficult, hence laboratory tests play a very important role in diagnosis. As performing sophisticated laboratory tests in resource-limited settings is not feasible, accurate point-of-care testing (POCT) for scrub typhus diagnosis would be invaluable for patient diagnosis and management. Here we summarise the existing evidence on the accuracy of scrub typhus POCTs to inform clinical practitioners in resource-limited settings of their diagnostic value.

METHODOLOGY/PRINCIPAL FINDINGS

Studies on POCTs which can be feasibly deployed in primary health care or outpatient settings were included. Thirty-one studies were identified through PubMed and manual searches of reference lists. The quality of the studies was assessed with the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2). About half (n = 14/31) of the included studies were of moderate quality. Meta-analysis showed the pooled sensitivity and specificity of commercially available immunochromatographic tests (ICTs) were 66.0% (95% CI 0.37-0.86) and 92.0% (95% CI 0.83-0.97), respectively. There was a significant and high degree of heterogeneity between the studies (I2 value = 97.48%, 95% CI 96.71-98.24 for sensitivity and I2 value = 98.17%, 95% CI 97.67-98.67 for specificity). Significant heterogeneity was observed for total number of samples between studies (p = 0.01), study design (whether using case-control design or not, p = 0.01), blinding during index test interpretation (p = 0.02), and QUADAS-2 score (p = 0.01).

CONCLUSIONS/SIGNIFICANCE

There was significant heterogeneity between the scrub typhus POCT diagnostic accuracy studies examined. Overall, the commercially available scrub typhus ICTs demonstrated better performance when 'ruling in' the diagnosis. There is a need for standardised methods and reporting of diagnostic accuracy to decrease between-study heterogeneity and increase comparability among study results, as well as development of an affordable and accurate antigen-based POCT to tackle the inherent weaknesses associated with serological testing.

Scrub Typhus and Its Causative Agent, Orientia tsutsugamushi

The obligate intracellular bacterium Orientia tsutsugamushi is responsible for more than one million cases of scrub typhus annually throughout the Asia-Pacific region. Human infection occurs via the bite of the larval form (chigger) of several species of trombiculid mites. While in some patients the result of infection is a mild, febrile illness, others experience severe complications, which may even be fatal. This review discusses the genome and biology of the causative agent, the changing epidemiology of scrub typhus, the challenges of its diagnosis, and current treatment recommendations.

Scrub typhus infection in pregnancy: the dilemma of diagnosis and treatment in a resource-limited setting

To save the life of both mother and fetus, the risks and benefits of the few antibiotics considered effective in the treatment of severe scrub typhus require consideration. In this case, chloramphenicol treatment averted maternal but not fetal mortality. Evidence‐based guidelines appropriate for resource‐limited endemic areas are required.