Neurological manifestations of scrub typhus infection: A systematic review and meta-analysis of clinical features and case fatality

Central nervous system infections in the tropics

PURPOSE OF REVIEW

Emerging and re-emerging central nervous system (CNS) infections are a major public health concern in the tropics. The reasons for this are myriad; climate change, rainfall, deforestation, increased vector density combined with poverty, poor sanitation and hygiene. This review focuses on pathogens, which have emerged and re-emerged, with the potential for significant morbidity and mortality.

RECENT FINDINGS

In recent years, multiple acute encephalitis outbreaks have been caused by Nipah virus, which carries a high case fatality. Arboviral infections, predominantly dengue, chikungunya and Zika are re-emerging increasingly especially in urban areas due to changing human habitats, vector behaviour and viral evolution. Scrub typhus, another vector borne disease caused by the bacterium Orientia tsutsugamushi , is being established as a leading cause of CNS infections in the tropics.

SUMMARY

A syndromic and epidemiological approach to CNS infections in the tropics is essential to plan appropriate diagnostic tests and management. Rapid diagnostic tests facilitate early diagnosis and thus help prompt initiation and focusing of therapy to prevent adverse outcomes. Vector control, cautious urbanization and deforestation, and reducing disturbance of ecosystems can help prevent spread of vector-borne diseases. Regional diagnostic and treatment approaches and specific vaccines are required to avert morbidity and mortality.

Case Report: Encephalitis with Initial Manifestation of Orientia Tsutsugamushi Infection Detected by Metagenomic Next-Generation Sequencing

Purpose

Scrub typhus, caused by Orientia tsutsugamushi, is characterized by fever, eschars, lymphadenopathy, and rash. The absence of eschars in some cases makes it difficult to distinguish it from other diseases, complicating the diagnosis process. Atypical Scrub typhus is difficult to diagnose and often leads to delayed treatment. Therefore, early diagnosis and treatment through effective detection methods have high clinical value. Here, a case of scrub typhus with encephalitis symptoms is reported.

Patients and Methods

A 64-year-old man and mNGS testing.

Results

A 64-year-old man developed cough, headache, and fever, dismissing it as a respiratory tract infection. Initial treatment with cephalosporin antibiotics had minimal effect. Admission to the respiratory department showed inflammation in blood tests. Subsequent CT and further treatment provided no improvement. Multidisciplinary discussions and neurology department guidance were conducted to consider the suspected diagnosis of encephalitis in the patient. After improving the mNGS detection, the patient was diagnosed with "Orientia tsutsugamushi encephalitis". After treatment with doxycycline, the patient's symptoms were alleviated. He remained afebrile in follow-up and adhered well to medical advice.

Conclusion

Our case demonstrates that it is difficult to distinguish Orientia tsutsugamushi encephalitis from central nervous system infectious diseases such as meningitis and encephalitis using conventional diagnostic methods, which may affect the treatment plan for the disease. mNGS is a useful and valuable method for early diagnosis of scrub typhus.

Molecular detection of Orientia tsutsugamushi in ectoparasites & their small mammal hosts captured from scrub typhus endemic areas in Madurai district, India

BACKGROUND OBJECTIVES

Scrub typhus, caused by Orientia tsutsugamushi present in small mammals harbouring the ectoparasites. A study was undertaken to detect the pathogen present in small mammals and its ectoparasites in the scrub typhus-reported areas.

METHODS

The small mammals (rodents/shrews) and its ectoparasites were screened for O. tsutsugamushi using nested PCR amplification of the groEL gene. Small mammals were collected by trapping and screened for ectoparasites (mites, ticks and fleas) by combing method.

RESULTS

All the chigger mites collected were tested negative for O. tsutsugamushi . Interestingly, adult non-trombiculid mites ( Oribatida sp., Dermanyssus gallinae ), fleas ( Xenopsylla astia, X. cheopis, Ctenophalides felis and Ctenophalides sp.) and ticks ( Rhipicephalus sanguineus , R. haemaphysaloides ) screened were found to be positive for O. tsutsugamushi , which the authors believe is the first report on these species globally. Bandicota bengalensis with O. tsutsugamushi infection is reported for the first time in India. The O. tsutsugamushi groEL sequences from the positive samples were similar to the reference strains, Karp and Ikeda and phylogenetically clustered in clade IV with less evolutionary divergence. The blood samples of Rattus rattus , Suncus murinus and B. bengalensis collected from this area were tested positive for O. tsutsugamushi ; interestingly, the sequence similarity was much pronounced with their ectoparasites indicating the transmission of the pathogen to host or vice versa .

INTERPRETATION CONCLUSIONS

The outcome of the present investigations widened our scope on the pathogens present in ectoparasites and rodents/shrews from this area. This will help to formulate the required vector control methods to combat zoonotic diseases.

Comparative analysis of diagnostic assays for scrub typhus: Unveiling enhanced approaches for accurate detection

The study comparatively evaluated serological assays, namely, Weil Felix assay, and IgM ELISA with the gold-standard immunofluorescence test (IFAT) for the sensitive and specific serodiagnosis of scrub typhus infection in occupationally exposed groups of humans. A total of 78 serum samples collected from persons affected with various ailments and belonging to different risk groups were screened in the study. Out of the 78 serum samples tested, a total of 17, 26, and 47 samples turned out to be positive by IFAT, IgM ELISA, and Weil Felix test, respectively. The Weil Felix assay could not serve as an ideal test for screening scrub typhus infection owing to its poor sensitivity and specificity in comparison with IFAT. IgM-ELISA could be an initial screening test to detect scrub typhus suspected patient in limited resource settings.

Clinical treatment of patients with scrub typhus-induced liver injury and intracranial infection

Scrub typhus is an infectious disease caused by Orientia tsutsugamushi, a bacterium within the family Rickettsiaceae. The clinical symptoms are usually acute and are characterized by fever, eschar formation or ulceration, local or generalized lymphadenopathy, and rash. Because of the extensive damage to small blood vessels throughout the body, scrub typhus can involve multiple systems and organs, causing damage to the respiratory, digestive, and nervous systems and inducing kidney and liver dysfunction. Death can occur in severe cases. We herein report two cases of scrub typhus with liver damage and intracranial infection. Among patients with scrub typhus, the risk of death is significantly higher in those who develop liver injury and intracranial infection. However, there are few reports on the treatment of patients with liver injury and intracranial infection caused by scrub typhus, and relevant treatment experience is thus lacking. Our clinical case report helps to fill the knowledge gap in this area.

Brain transcriptomics reveal the activation of neuroinflammation pathways during acute Orientia tsutsugamushi infection in mice

Scrub typhus, an acute febrile illness caused by Orientia tsutsugamushi (Ot), is prevalent in endemic areas with one million new cases annually. Clinical observations suggest central nervous system (CNS) involvement in severe scrub typhus cases. Acute encephalitis syndrome (AES) associated with Ot infection is a major public health problem; however, the underlying mechanisms of neurological disorder remain poorly understood. By using a well-established murine model of severe scrub typhus and brain RNA-seq, we studied the brain transcriptome dynamics and identified the activated neuroinflammation pathways. Our data indicated a strong enrichment of several immune signaling and inflammation-related pathways at the onset of disease and prior to host death. The strongest upregulation of expression included genes involved in interferon (IFN) responses, defense response to bacteria, immunoglobulin-mediated immunity, IL-6/JAK-STAT signaling, and TNF signaling via NF-κB. We also found a significant increase in the expression of core genes related to blood-brain barrier (BBB) disruption and dysregulation in severe Ot infection. Brain tissue immunostaining and in vitro infection of microglia revealed microglial activation and proinflammatory cytokine production, suggesting a crucial role of microglia in neuroinflammation during scrub typhus. This study provides new insights into neuroinflammation in scrub typhus, highlighting the impact of excessive IFN responses, microglial activation, and BBB dysregulation on disease pathogenesis.

Scrub typhus, a salient threat: Needs attention

Scrub typhus (ST) infection is one of the most significant causes of acute undifferentiated febrile illness, and its prevalence has been increasing across the globe. Clinical suspicion and growing clinical understanding among healthcare professionals have resulted in the rapid diagnosis and effective management. Since ST has the potential to cause multiorgan failure and a higher mortality rate, it is critical to enhance surveillance, make rapid diagnosis, and administer antibiotics appropriately.