Rickettsioses as Major Etiologies of Unrecognized Acute Febrile Illness, Sabah, East Malaysia

Health facility-based prevalence of typhoid fever, typhus and malaria among individuals suspected of acute febrile illnesses in Southwest Region, Ethiopia

Background

Acute febrile illnesses such as typhoid fever, typhus, and malaria are still major causes of hospital admission in many parts of Ethiopia. However, there are substantial gaps in the monitoring systems, which result in a lack of knowledge about the geographic distribution and role of common pathogens, particularly in rural areas. Thus, this study was aimed at assessing the seroprevalence of typhoid fever, typhus, and malaria among suspected acute febrile patients at the MTU Teaching Hospital and Mizan-Aman Health Center, Southwest region of Ethiopia.

Method

A health facility-based cross-sectional study was carried out from July to October 2022. Blood samples were collected from a total of 384 individuals. Widal and Weilfelix direct card agglutination and tube agglutination test methods were used for the Salmonella enterica serotype Typhi (S. typhi) and Rickettsia infections. The diagnosis of malaria was made using thick and thin blood smears. Questionnaires given by interviewers were used to gather information on risk factors and other sociodemographic factors. The data was analyzed using STATA/SE 14.0.

Result

A total of 371 patients were tested for S. Typhi and Rickettsia infections using direct card agglutination and tube agglutination methods. Using the screening test, 20.5% (76/371) patients were reactive either for O or H antigens or both, of which 55.3% (42/76) were reactive by the titration test at the cutoff value ≥ 1:80. About 17.5% (65/371) were reactive to OX19 antigen by card agglutination test, and of which 58.5% (38/65) were reactive by the titration test at the cutoff value ≥ 1:80. The overall seroprevalence of S. Typhi and Rickettsia infections using combined direct card and tube agglutination techniques was 11.3% (42/371) and 10.2% (38/371), respectively. Out of 384 suspected malaria patients, 43 (11.2%) were found positive either for P. falciparum, 27 (7.03%), or P. vivax, 16 (4.2%).

Conclusion

In this study, typhoid fever, typhus, and malaria were found among symptomatic acute febrile patients. To increase disease awareness, it is necessary to provide sustainable health education about risk factor behaviors, disease transmission, and prevention strategies. In addition, improving laboratory diagnosis services and early treatment may also lower the likelihood of potentially fatal consequences.

Identification of Bacteria and Viruses Associated with Patients with Acute Febrile Illness in Khon Kaen Province, Thailand

The majority of cases of undifferentiated acute febrile illness (AFI) in the tropics have an undefined etiology. In Thailand, AFI accounts for two-thirds of illnesses reported to the Ministry of Public Health. To characterize the bacterial and viral causes of these AFIs, we conducted molecular pathogen screening and serological analyses in patients who sought treatment in Chum Phae Hospital, Khon Kaen province, during the period from 2015 to 2016. Through integrated approaches, we successfully identified the etiology in 25.5% of cases, with dengue virus infection being the most common cause, noted in 17% of the study population, followed by scrub typhus in 3.8% and rickettsioses in 6.8%. Further investigations targeting viruses in patients revealed the presence of Guadeloupe mosquito virus (GMV) in four patients without other pathogen co-infections. The characterization of four complete genome sequences of GMV amplified from AFI patients showed a 93-97% nucleotide sequence identity with GMV previously reported in mosquitoes. Nucleotide substitutions resulted in amino acid differences between GMV amplified from AFI patients and mosquitoes, observed in 37 positions. However, these changes had undergone purifying selection pressure and potentially had a minimal impact on protein function. Our study suggests that the GMV strains identified in the AFI patients are relatively similar to those previously reported in mosquitoes, highlighting their potential role associated with febrile illness.

Serological profile of patients suspected with non-scrub typhus rickettsioses

BACKGROUND

Rickettsial pathogens are Gram-negative, obligate intracellular bacteria. They are transmitted by arthropods and are responsible for a wide variety of disease, from minor to life-threatening, which have a global effect on human health. Limited data are available on the prevalence of rickettsial diseases from India, and the disease epidemiology is not fully described. This study aimed to diagnose non-scrub typhus rickettsioses including spotted fever and typhus group of Rickettsia in clinically suspected patients by using standard serological tests and recognition of common epidemiological conditions and clinical manifestations.

METHODS

During the study period, a total of 700 patients of all ages with acute febrile illness were enrolled. Patients were screened for rickettsial infection using IgM Enzyme-linked immunosorbent assay (ELISA) and Immunofluorescence assay (IFA) was performed to confirm the ELISA positive results. The relevant demographic, clinical, and laboratory details of patients were documented and analyzed.

RESULTS

Of 700 samples tested, 141 (20.2%) were found to be positive for IgM antibodies against rickettsioses using ELISA and IFA. SFGR was positive in 15 (2.2%), TGR was positive in 112 (16%) and 14 (2%) samples were positive for both groups. 20 (14.2%) patients required admission to the intensive care unit (ICU), and 24 (17%) in-hospital deaths occurred.

CONCLUSIONS

The prevalence of rickettsioses in India appears to be underestimated; therefore, increased awareness and improved diagnostic testing could facilitate early detection of cases, pathogen-targeted appropriate treatment, and improved outcomes for patients. Despite the fact that Rickettsiae can be isolated or detected using molecular techniques in clinical specimens, serology still remains the most commonly used diagnostic method for rickettsioses around the world. Our study helps bridge the gap of limited data on Rickettsia in north India and could be useful for future epidemiological investigation of rickettsial diseases and outbreaks.

Geographical distribution of scrub typhus and risk of Orientia tsutsugamushi infection in Indonesia: Evidence mapping

BACKGROUND

Scrub typhus is a potentially fatal acute febrile illness caused by bacteria in the genus Orientia. Though cases have been documented, a comprehensive body of evidence has not previously been compiled to give an overview of scrub typhus in Indonesia. This study aimed to address this key knowledge gap by mapping and ranking geographic areas based on existing data on the presence or absence of the pathogen in humans, vectors, and host animals.

METHODOLOGY/PRINCIPAL FINDINGS

We performed searches on local and international electronic databases, websites, libraries, and collections including Embase, Medline, and Scopus to gather relevant evidence (including grey literature). After extracting data on the presence and absence of the pathogen and its vectors, we ranked the evidence based on the certainty for the presence of human infection risk. The country was divided into subnational units, and each were assigned a score based on the evidence available for that unit. We presented this in an evidence map. Orientia tsutsugamushi presence has been identified on all the main islands (Sumatra, Java, Borneo, Celebes, Papua). About two thirds of the data points were collected before 1946. South Sumatra and Biak had the strongest evidence for sustaining infectious vectors. There was only one laboratory confirmed case in a human identified but 2,780 probable cases were documented. The most common vector was Leptotrombidium deliense.

CONCLUSIONS/SIGNIFICANCE

Our review highlights the concerning lack of data on scrub typhus in Indonesia, the fourth most populous country in the world. The presence of seropositive samples, infected vectors and rodents confirm O. tsutsugamushi is widespread in Indonesia and likely to be causing significant morbidity and mortality. There is an urgent need to increase surveillance to better understand the burden of the disease across the archipelago and to inform national empirical fever treatment guidelines.

Habitat and Season Drive Chigger Mite Diversity and Abundance on Small Mammals in Peninsular Malaysia

Chigger mites are vectors of the bacterial disease scrub typhus, caused by Orientia spp. The bacterium is vertically transmitted in the vector and horizontally transmitted to terrestrial vertebrates (primarily wild small mammals), with humans as incidental hosts. Previous studies have shown that the size of the chigger populations is correlated with the density of small mammals in scrub typhus-endemic regions. Here, we explore interactions between the small mammals and chiggers in two oil palm plantations located in the Perak and Johor states of Peninsular Malaysia. The location in Perak also contained an aboriginal (Orang Asli) settlement. A ~5% sub-sample from 40,736 chigger specimens was identified from five species of small mammals (n = 217), revealing 14 chigger species, including two new records for Malaysia. The abundance and species richness of chiggers were significantly affected by habitat type (highest in forest border), state (highest in Perak), and season (highest in dry). The overall prevalence of Orientia tsutsugamushi DNA in small-mammal tissues was 11.7% and was not significantly affected by host or habitat characteristics, but in Johor, was positively associated with infestation by Leptotrombidium arenicola. These findings highlight the risk of contracting scrub typhus in oil palm plantations and associated human settlements.

Rickettsiosis in Southeast Asia: Summary for International Travellers during the COVID-19 Pandemic

Rickettsiosis is an important cause of febrile illness among travellers visiting Southeast Asia (SEA). The true incidence of rickettsiosis is underestimated; however, murine typhus and scrub typhus are widely distributed across SEA. Among travellers visiting SEA, scrub typhus was mostly reported from Thailand, whereas murine typhus was frequently found in Indonesia. Although most cases are self-limited or present with mild symptoms, a few cases with severe clinical manifestations have been reported. Doxycycline remains the key treatment of rickettsiosis. Some travellers, such as backpackers, trekkers, or cave explorers, are at a higher risk for rickettsiosis than others. Therefore, in resource-limited conditions, empirical treatment should be considered in these travellers. The coronavirus disease 2019 (COVID-19) pandemic has contributed to difficulty in the diagnosis of rickettsiosis because of the clinical similarities between these diseases. In addition, physical distancing mandated by COVID-19 management guidelines limits accurate physical examination, resulting in misdiagnosis and delayed treatment of rickettsiosis. This review summarises the characteristics of murine typhus and scrub typhus, describes travel-associated rickettsiosis, and discusses the impact of the COVID-19 pandemic on rickettsiosis.

An Update on the Laboratory Diagnosis of Rickettsia spp. Infection

Rickettsia species causing human illness are present globally and can cause significant disease. Diagnosis and identification of this intracellular bacteria are challenging with many available diagnostic modalities suffering from several shortcomings. Detection of antibodies directed against Rickettsia spp. via serological methods remains widely used with a broad range of sensitivity and specificity values reported depending on the assay. Molecular methods, including polymerase chain reaction (PCR) testing, enables species-specific identification with a fast turnaround time; however, due to resource requirements, use in some endemic settings is limited. Reports on the use of next-generation sequencing (NGS) and metagenomics to diagnose Rickettsia spp. infection have been increasing. Despite offering several potential advantages in the diagnosis and surveillance of disease, genomic approaches are currently only limited to reference and research laboratories. Continued development of Rickettsia spp. diagnostics is required to improve disease detection and epidemiological surveillance, and to better understand transmission dynamics.

Spotted fever diagnosis: Experience from a South Indian center

Spotted fever (SF) is an important treatable cause of acute febrile illness (AFI) with rash and has reemerged in India. A prospective AFI with rash study was undertaken at a South Indian hospital to correlate specific clinical findings with laboratory confirmation of spotted fever. During the study period (December 2017 to May 2019), 175 patients with fever and rash were suspected to have spotted fever. Molecular assays for scrub typhus and spotted fever (47 kDa and ompA qPCR) and serology (IgM ELISA) was performed on the 96 individuals recruited. Laboratory confirmed SF cases (ompA qPCR positive) were 21, whereas laboratory supported SF cases (ompA negative but sero-positive by SF IgM ELISA) were 27. Among the 48 spotted fever (SF) cases, 70% of had maculopapular rash, 12.5% had macular rash, purpuric/petechial rash (severe rash) was seen in 8 patients (16.7%). Presence of rash on the palms and soles was associated with a relative risk (RR) of 4.36 (95% CI: 2.67-7.10; p < 0.001). Our study suggests that ompA qPCR though useful for confirming the diagnosis of spotted fever is not always positive. A positive SF IgM ELISA in febrile individuals with palmo-plantar rash supports the diagnosis of spotted fever especially when other causes of febrile rash have been excluded. Multi-centric prospective studies employing the serological reference standard, IFA (immunofluorescence assay) in addition to the assays used in this study are needed to validate these findings.