Molecular characterization and evolutionary analysis of Orientia tsutsugamushi in eastern Indian population

Deciphering the genotypic diversity and epidemiology of scrub typhus genotypes in India: A systematic review and meta-analysis

BACKGROUND

Scrub typhus is a significant cause of Acute Febrile Illness in India and presents a range of clinical manifestations influenced by the genotypes of the causative agent, Orientia tsutsugamushi. Understanding the distribution of these genotypes is crucial for public health planning, diagnostic accuracy, and vaccine development.

METHODS

In this systematic review, we analyzed 18 studies from an initial pool of 2013 records identified through database searches following PRISMA guidelines. The relevance of the findings to the genotype prevalence of Scrub typhus in India was taken into consideration throughout the selection process. Various genotyping methods, predominantly Polymerase Chain Reaction (PCR), were used in these studies to identify genotypes such as Karp, Gilliam, Kato, and others.

RESULTS

The review revealed diverse prevalence rates of Scrub typhus genotypes across different Indian states. The Karp genotype is the most prevalent in India, with a pooled prevalence of 47 %, followed by the Kato genotype at 40 % and the Gilliam genotype at 28 %. The Karp genotype showed significant variability, with prevalence rates ranging from 100 % in Andhra Pradesh (2018) to 6.16 % in Uttar Pradesh (2016-2017). The Kato genotype's presence varied significantly, with high prevalence in certain states like Karnataka and absence in others like Andhra Pradesh. The Gilliam genotype also displayed a unique distribution pattern, dominating in Uttar Pradesh with a prevalence of 93.8 % in some years. Other genotypes like Boryong, IHS-II, Neimeng, Kuroki, TA763, and Kawasaki also showed varied prevalence across states. There was significant heterogeneity in the prevalence rates of different genotypes among studies, as indicated by I2 statistics.

CONCLUSION

The diversity in Scrub typhus genotypes across India underscores the disease's complex epidemiology, presenting diagnostic challenges and opportunities for targeted public health interventions. For efficient disease management and control plans in India, it is imperative to understand the changing genetic landscape of scrub typhus through ongoing study and surveillance.

Development and implementation of a strategy for early diagnosis and management of scrub typhus: an emerging public health threat

Scrub typhus, caused by Orientia tsutsugamushi, is a re-emerging zoonotic disease in the tropics with considerable morbidity and mortality rates. This disease, which is mostly prevalent in rural areas, remains underdiagnosed and underreported because of the low index of suspicion and non-specific clinical presentation. Limited access to healthcare, diagnostics, and treatment in rural settings further makes it challenging to distinguish it from other febrile illnesses. While easily treatable, improper treatment leads to severe forms of the disease and even death. As there is no existing public health program to address scrub typhus in India, there is an urgent need to design a program and test its effectiveness for control and management of the disease. With this backdrop, this implementation research protocol has been developed for a trial in few of the endemic "pockets" of Odisha, an eastern Indian state that can be scalable to other endemic areas of the country, if found effective. The main goal of the proposed project is to include scrub typhus as a differential diagnosis of fever cases in every tier of the public health system, starting from the community level to the health system, for the early diagnosis among suspected cases and to ensure that individuals receive complete treatment. The current study aimed to describe the protocol of the proposed Scrub Typhus Control Program (STCP) in detail so that it can receive valuable views from peers which can further strengthen the attempt.

Identification of Talaromyces marneffei Infection in an HIV-Negative Patient by ITS Sequencing

Disseminated ankle mycosis is a life-threatening systemic infection caused by the emerging opportunistic and lethal fungal pathogen Talaromyces marneffei which is more common in HIV-positive patients. However, an increasing number of infections are occurring in HIV-negative patients. Here, we report a case of Talaromyces marneffei infection in HIV-negative patient. A 50s HIV-negative male patient with fever, cough, bloody sputum expectoration, pulmonary sarcoidosis and body rashes was hospitalized at Zhejiang Provincial People's Hospital. CT scanning showed pulmonary multiple nodules with apical bronchial occlusion, patchy infiltration and pathological biopsy demonstrated bronchiolitis obliterans with organized pneumonia and chronic active inflammation of lung tissue with infiltration of numerous lymphocytes, plasma cells, phagocytes and neutrophils. Laboratory tests revealed significantly increased white blood cells count 18.3 ×109/L, neutrophil count 15.34 ×109/L, monocyte count 0.66 ×109/L, platelet count 517 ×109/L, C-reactive protein 116 mg/L, erythrocyte sedimentation rate 112mm/h. The β-D-glucan test was negative (33.06 pg/mL) while fungal culture of broncho alveolar lavage fluid revealed colonies with temperature-dependent dimorphic growth character and Talaromyces marneffei was confirmed by ITS sequencing of the colonies. The patient exhibited radiological improvement and clinical recuperation after intravenously guttae of voriconazole. Talaromycosis in immunocompetent and HIV-negative individuals is relatively rare and is characterized by an insidious onset, various clinical manifestations, and is clinically challenging. Fungal culture and ITS sequencing are warranted for diagnosis Talaromyces marneffei infection. This is the first report on identification of Talaromyces marneffei infection in an HIV-negative patient with skin involvement by ITS sequencing in Zhejiang.

Gene expression and involvement of signaling pathways during host-pathogen interplay in Orientia tsutsugamushi infection

Scrub typhus is a neglected tropical disease that affects one-third of the world’s population. The disease is caused by Orientia tsutsugamushi (OT), an obligate intracellular Gram-negative bacterium. OT efficiently escapes from the endosomal pathway after entering the host cell and replicates inside cytosol. OT infection promotes cellular autophagy, the autonomous defense mechanism unlike other bacteria. This study has discussed the bacterial invasion process through the extracellular matrix and the immune response activated by the bacterium within the hosts. Furthermore, we have emphasized the importance of extracellular matrix and their cross-talk with the immune cells, such as, macrophages, neutrophils, and dendritic cells followed by their inflammatory response. We have also put an insight into the host factors associated with signaling pathways during scrub typhus disease with a special focus on the OT-induced stress response, autophagy, apoptosis, and innate immunity. Multiple cytokines and chemokines play a significant role in activating different immune-related signaling pathways. Due to the presence of high antigenic diversity among strains, the signaling pathways during the host–pathogen interplay of OT with its host is very complicated. Thus, it hinders to mitigate the severity of the pandemic occurred by the respective pathogen. Our investigation will provide a useful guide to better understand the virulence and physiology of this intracellular pathogen which will lead towards a better therapeutic diagnosis and vaccine development.