Tricky typhus ticks two: A report of two sisters from North India presenting with acute respiratory distress syndrome due to scrub typhus

Scrub typhus is emerging as an important cause of acute febrile illness in Northern India. This is a report of two sisters presenting concurrently with acute respiratory distress syndrome. A diagnosis of scrub typhus was made in both the patients, and they were successfully treated with doxycycline.     

Outbreak of scrub typhus in the North East Himalayan region-Sikkim: An emerging threat

Scrub typhus is an acute febrile illness that is known to be endemic in the South East Asian countries and the Western Pacific region. We here report an outbreak in the tiny Himalayan state of Sikkim. Patients with pyrexia of unknown origin were evaluated. They were screened by Weil–Felix test and the rapid immunochromatographic method. Samples that were positive by either Weil–Felix agglutination test or by rapid immunochromatography were confirmed by IgM enzyme-linked immunosorbent assay (ELISA). A total 204 samples were screened. Sixty-three patients were confirmed positive among which 42 were male and 21 were female. Effective management and early administration of antibiotics will help prevent the complications and mortality associated with scrub typhus.     

Scrub typhus in patients with liver cirrhosis: a preliminary study

Scrub typhus is a potentially fatal infectious disease caused by the organism Orientia tsutsugamushi. However, to date, there have been no clearly identified determinants or reports published on the clinical severity of scrub typhus in liver cirrhosis (LC) patients. This study was carried out by retrospectively reviewing medical records accumulated over 7 years at a tertiary hospital. Sixteen patients of 160 had underlying LC, and they were defined as ‘cases'; those without underlying LC were defined as ‘controls'. The duration of hospital stay (23.0 ± 24.8 days for cases and 6.8 ± 7.0 days for controls, p 0.020) and APACHE II scores (14.1 ± 6.0 for cases and 7.2 ± 4.6 for controls, p <0.001) were, respectively, significantly longer and significantly higher on admission in the cases than in the controls. Surprisingly, hospital mortality was significantly higher in the cases than in the controls (31.3% and 3.5%, respectively, p 0.001). Among the LC group, the highest Model for End-stage Liver Disease (MELD) score during hospitalization (MELD-Peak) (p 0.024) and the lowest blood sodium concentration during hospitalization (MELD-Na-Lo) (p 0.003) were higher in fatal cases than in the survivors (MELD-Na-to). Physicians should be aware of an adverse relationship between LC and scrub typhus, and patients with LC should be advised to avoid exposure to O. tsutsugamushi, particularly in endemic areas and epidemic seasons.     

Scrub typhus and spotted fever among hospitalised children in South India: Clinical profile and serological epidemiology

Background: Rickettsial infections are re-emerging. In India, they are now being reported from several areas where they were previously unknown. Objectives: The objective of this study was to describe the epidemiology, clinical profile and outcome of serologically-confirmed scrub typhus and spotted fever among children in a tertiary care hospital in Bengaluru. Materials and Methods: Hospitalised children aged <18 years, with clinical features suggestive of rickettsial disease admitted between January 2010 and October 2012 were included prospectively. Diagnosis was based on scrub typhus and spotted fever-specific IgM and IgG by enzyme-linked immunosorbent assay (ELISA). Results: Of 103 children with clinical features suggestive of rickettsial illness, ELISA test confirmed 53 cases for scrub typhus, 23 cases for spotted fever group and 14 with mixed infection. The average age was 7.3 (±3.9) years and 44 (71.0%) children were male. Majority of cases were from Karnataka (50%), Andhra Pradesh (32.3%) and Tamil Nadu (17.7%). Common clinical features included fever (100%, average duration 11 days), nausea and vomiting (44%), rash (36%); eschar was rare. Compared to the ELISA test, Weil-Felix test (OX-K titre of 1:80) had a sensitivity and specificity of 88.7% and 43.9%, respectively. Treatment with chloramphenicol or doxycycline was given to the majority of the children. Complications included meningoencephalitis (28%), shock (10%), retinal vasculitis (10%) and purpura fulminans (7%). Conclusions: These findings suggest that the burden of rickettsial infection among children in India is high, with a substantially high complication rate. Rickettsial-specific ELISA tests can help in early diagnosis and early institution of appropriate treatment that may prevent life-threatening complications.     

Possibility of scrub typhus in fever of unknown origin (FUO) cases: An experience from Rajasthan

Purpose: Fever of unknown origin (FUO) has multiple causes. Scrub typhus is less known cause of FUO in India. The present study reports a recent epidemic of scrub typhus amongst cases of FUO from different areas of Rajasthan, India. There was high mortality in undiagnosed cases of FUO which lead to the diagnosis of scrub typhus. Objective: To study the possibility of scrub typhus as a causative factor in FUO cases by qualitative detection of IgM antibodies with ELISA. Materials and Methods: From September 2012 to December 2012, 271 serum samples of FUO cases were analysed for IgM antibodies to Orientia tsutsugamushi along with dengue, malaria, typhoid, tuberculosis and brucellosis. Results: Scrub typhus IgM antibodies by ELISA were detected in 133 (49.1%) patients. Scrub typhus positivity was significantly higher among female in comparison to males (P < 0.05). Maximum positivity of scrub typhus was found in females of 46-60 years age group. The laboratory parameters were abnormal in most of the patients as evident by thrombocytopenia (63%), deranged liver functions (56%) and renal functions (25%). Conclusion: The present study emphasises the importance of scrub typhus among cases of FUO especially after rainy season and during early cooler months. The study also highlights the significance of ELISA method for rapid and early reporting and ruling out scrub typhus in FUO cases.     

Risk-factors for human infection with Orientia tsutsugamushi: a case-control study in Korea.

A case-control study was conducted involving 156 patients with scrub typhus and 130 controls. Three factors were associated significantly with the risk of developing scrub typhus: engaging in fruit farming (OR 2.44; 95% CI 1.04-5.69), gathering chestnuts (OR 2.05; 95% CI 1.09-3.87) and taking breaks in areas adjacent to agricultural operations (OR 3.06; 95% CI 1.50-6.22). In contrast, receiving information or educational materials concerning the prevention of scrub typhus had a protective effect (OR 0.45; 95% CI 0.24-0.83). These results suggest that a health education programme will lower the risk of developing scrub typhus when applied to high-risk groups.     

Seroprevalence of Scrub typhus at a tertiary care hospital in Andhra Pradesh

Introduction: Scrub typhus is a rickettsial infection which is caused by Orientia tsutsugamushi and transmitted by the bite of the chigger of a mite. Delay in diagnosis can be fatal otherwise the treatment is simple, doxycycline being the drug of choice. Indirect immunoflurescence is considered gold standard but it is not used in India as it is costly and also not available. There is need for rapid, economic and simple test for the diagnosis of scrub typhus. This study was taken up to study the seroprevalence of scrub typhus in Andhra Pradesh and to compare two commonly used serological methods; rapid test and IgM ELISA. Materials and methods: This is a prospective study in which 100 serum samples from clinically suspected cases collected over a period of 3 months were processed for the detection of IgM antibodies for scrub typhus by ELISA and Rapid test. Samples were also tested for leptospirosis and dengue fever which the other common causes of fever prevalent in this region. Results: Total number of samples processed was 100 of which 52 were males and 48 females. Among the hundred samples 39 were seropositive. Positivity was higher in the age group of patients between 16 and 30 yrs of age. There was 97% correlation between ELISA and rapid method. Of the 100 samples only three samples positive by ELISA were negative by rapid method. Fever was the most common manifestation and there was no eschar and no mortality reported. Conclusion: Scrub typhus should be included in the differential diagnosis of fever of unknown origin along with dengue, malaria and leptospirosis which are the other common endemic infections in this part of the country.     

Co-infection of scrub typhus and leptospirosis in patients with pyrexia of unknown origin in Longding district of Arunachal Pradesh in 2013

Background: Scrub typhus and leptospirosis are bacterial zoonotic disease causing high morbidity and mortality. The seasonal outbreak of pyrexia is common in Arunachal Pradesh (AP); many times the disease remains undiagnosed. Objective: An outbreak of pyrexia of unknown origin (PUO) occurred in Longding district of Arunachal Pradesh in 2013, with 108 deaths, which was investigated to elucidate the cause of illness. Methodology: Blood samples from the affected region with acute pyrexia were collected, and screened for the malaria parasite, scrub typhus IgM and leptospira IgM. Results: Scrub typhus IgM was reactive in 97% (30/31), and 25% (8/31) cases were co-infected with leptospira. Incidentally, scrub typhus reactive (67%) and leptospira co-infection (62.7%) were higher in females. Record of previous 3 years (2011–2013) from Longding, Community Health Centre showed an increase in indoor pyrexia cases by 2-fold or more during October and November. Conclusion: The present study is the first report of co-infection of scrub typhus with leptospirosis from Northeast India. Medical officers in this region should take scrub typhus and leptospirosis in their differential diagnosis of patients with PUO for early diagnosis and effective treatment.     

Impact of influenza virus escape‐mutations on influenza detection by the rapid influenza diagnostic test

During the influenza pandemic of 2009–2010, rapid influenza diagnostic tests (RIDTs) were used to detect influenza viral infections because they are quick and simple to use. However, retrospective studies showed that RIDTs performed poorly when used to diagnose pandemic viral infections. Determining how amino acid sequence changes in pandemic or epidemic influenza viral antigens impact clinical value of RIDTs has not been possible, because the viral epitopes recognized by RIDTs have been not mapped. In this study, the effect of escape‐variations or mutations in influenza viral antigens upon the sensitivity and specificity of an RIDT was investigated by characterizing the immunological properties of the antibodies used in the RIDT. Escape‐mutants were generated by cultivating A/Korea/01/2009 in the presence of an excess of the same antibodies used in the RIDT. Escape‐mutants not recognized by the RIDT were selected. Epitopes recognized by the RIDT were mapped by comparing the sequence and immunological analysis of the escape‐variants and wild‐type isolates. The RIDT antibodies recognized epitopes on the Sa antigenic site and in the F subdomain in hemagglutinin. Variants bearing mutations in these epitopes were not detected by the RIDT. The frequency of escape‐variants emerging since the 2009–2010 pandemic was calculated as 1.27% using in silico surveillance of influenza sequence databases. These results suggest that mapping the relevant epitopes of RIDTs and making such information available to clinics would be helpful for determining whether RIDTs match newly emergent strains and subtypes prior to retrospective re‐evaluation of the RIDTs using clinical specimens. J. Med. Virol. 85:709–715, 2013. © 2013 Wiley Periodicals, Inc.     

Nested polymerase chain reaction on blood clots for gene encoding 56 kDa antigen and serology for the diagnosis of scrub typhus

Purpose: Scrub typhus is a zoonotic illness endemic in the Asia-Pacific region. Early diagnosis and appropriate management contribute significantly to preventing adverse outcomes including mortality. Serology is widely used for diagnosing scrub typhus. Recent reports suggest that polymerase chain reaction (PCR) could be a rapid and reliable alternative. This study assessed the utility of these tests for scrub typhus diagnosis. Materials and Methods: Nested PCR to detect the 56 kDa antigen gene of O. tsutsugamushi was performed on blood clots from 87 individuals with clinically suspected scrub typhus. Weil-Felix test and scrub typhus IgM ELISA were performed on serum samples from the same patients. As a gold standard reference test was not available, latent class analysis (LCA) was used to assess the performance of the three tests. Results: The LCA analysis showed the sensitivity of Weil-Felix test, IgM ELISA and PCR to be 59%, 100% and 58% respectively. The specificity of ELISA was only 73%, whereas those of the Weil-Felix test and PCR were 94% and 100% respectively. Conclusion: Nested PCR using blood clots while specific, lacked sensitivity as compared to IgM ELISA. In resource-poor settings Weil-Felix test still remains valuable despite its moderate sensitivity.     

Characteristics of scrub typhus,murine typhus,and Q fever among elderly patients: Prolonged prothrombin time as a predictor for severity

Background/purpose

The clinical manifestations of scrub typhus, murine typhus and acute Q fever in the elderly are not clear.

恙虫病东方体Sta56抗原的原核表达、纯化及其在间接ELISA中的应用

目的　构建含恙虫病东方体sta5 6基因的重组表达质粒 ,在E .coli中表达Sta5 6重组抗原 ,纯化后用于间接ELISA检测恙虫病。方法　从含有恙虫病东方体Karp株sta5 6基因的重组质粒TOPO sta5 6扩增出截短的sta5 6 ,定向插入pET30a载体 ,转化大肠杆菌BL2 1(DE3) ,IPTG诱导表达 ,用SDS PAGE及Westernblot进行分析 ;采用电洗脱方法纯化重组抗原并应用于间接ELISA检测恙虫病。结果　以截短的sta5 6基因片段构建了重组表达质粒pETOt95 7,重组的Sta5 6抗原可在E .coli中以融合蛋白的形式有效表达 ,SDS PAGE显示了一条相对分子质量 (Mr)为 4 0 .3× 10 3 的蛋白表达带 ,West ernblot证实该融合蛋白能被恙虫病患者阳性血清所识别。电洗脱纯化的重组抗原应用于间接法ELISA检测恙虫病 ,与间接免疫荧光法IFAT比较 ,其敏感性和特异性分别为 91.7%和 76 .5 %。结论　在大肠杆菌中表达的Sta5 6重组抗原具有免疫反应性 ,纯化后可用作免疫诊断试剂。     

Rose Bengal test: diagnostic yield and use for the rapid diagnosis of human brucellosis in emergency departments in endemic areas

The aim of the present study was to analyse the diagnostic yield of the rose Bengal test for the rapid diagnosis of human brucellosis in an emergency department in an area where the disease is endemic. The study included 711 patients diagnosed initially with brucellosis and 270 controls. Brucellosis patients were divided into three groups: group I, individuals with no regular exposure to or history of brucellosis; group II, individuals exposed repeatedly to Brucella infection; and group III, individuals infected with Brucella who had received appropriate treatment during the previous 12 months. Blood cultures were positive for 445 (62.6%) brucellosis patients, while the remaining 266 (37.4%) patients were diagnosed according to clinical and serological criteria. The overall sensitivity of the rose Bengal test was 92.9%. The specificities for groups I, II and III were 94.3%, 91.7% and 76.9%, respectively, with positive likelihood ratios of 16.5, 10.4 and 4.2, respectively. The diagnostic gain after the performance of the rose Bengal test was good or very good in patients with no previous exposure to Brucella or history of brucellosis, but poor in patients who were exposed repeatedly to Brucella or had a history of brucellosis and a low pre-test probability. Use of the rose Bengal test as the sole technique for the diagnosis of brucellosis in endemic areas should be considered very carefully in the context of patients who are exposed repeatedly to Brucella or have a history of brucellosis.     

Diagnostic accuracy of antibody-based rapid diagnostic tests in detecting coronavirus disease 2019: systematic review

IntroductionThe rapid transmission of coronavirus disease 2019 (COVID-19) requires a fast, accurate, and affordable detection method. Despite doubts of their diagnostic accuracy, rapid diagnostic tests (RDTs) are used worldwide due to their practicality. This systematic review aims to determine the diagnostic accuracy of antibody-based RDTs in detecting COVID-19.Material and methodsA literature search was carried out on five journal databases using the PRISMA-P 2015 method. We included all studies published up to February 2021. The risk of bias was evaluated using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Diagnostic Test Accuracy Studies. Data regarding peer-review status, study design, test kit information, immunoglobulin class, target antigen, and the number of samples were extracted and tabulated. We estimated the pooled sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) with a 95% confidence interval.ResultsThirty-three studies met the eligibility criteria. The pooled data results showed that the combined detection method of IgM or IgG had the highest sensitivity and NPV, which were 73.41% (95% CI: 72.22–74.57) and 75.34% (95% CI: 74.51–76.16), respectively. The single IgG detection method had the highest specificity and PPV of 96.68% (95% CI: 96.25–97.07) and 95.97% (95% CI: 95.47–96.42%), respectively.ConclusionsAntibody-based RDTs are not satisfactory as primary diagnostic tests but have utility as a screening tool.     

Malaria rapid diagnostic tests in travel medicine

Malaria is a serious condition in the non-immune traveller, and prognosis depends on timely diagnosis. Although microscopy remains the cornerstone of diagnosis, malaria rapid diagnostic tests (RDTs) are increasingly used in non-endemic settings. They are easy to use, provide results rapidly and require no specific training and equipment. Reported sensitivities vary between different RDT products but are generally good for Plasmodium falciparum, with RDTs detecting the P. falciparum antigen histidine-rich protein-2 (PfHRP2) scoring slightly better than P. falciparumlactate dehydrogenase (Pf-pLDH)-detecting RDTs. Sensitivity is lower for Plasmodium vivax (66.0 – 88.0%) and poor for Plasmodium ovale (5.5 – 86.7%) and Plasmodium malariae (21.4 – 45.2%). Rapid diagnostic tests have several other limitations, including persistence of the PfHRP2 antigen, cross-reactions of P. falciparum with the non-falciparum test line and vice versa and (rare) false-positive reactions due to other infectious agents or immunological factors. False-negative results occur in the case of low parasite densities, prozone effect or pfhrp2 gene deletions. In addition, errors in interpretation occur, partly due to inadequacies in the instructions for use. Finally, RDTs do not give information about parasite density. In the diagnostic laboratory, RDTs are a valuable adjunct to (but not a replacement for) microscopy for the diagnosis of malaria in the returned traveller.In malaria endemic settings, special groups of travellers (those travelling for long periods, expatriates and short-stay frequent travellers) who are remote from qualified medical services may benefit from self-diagnosis by RDTs, provided they use correctly stored RDT products of proven accuracy, with comprehensive instructions for use and appropriate hands-on training.     

Epidemiological,clinical and genetic characterization of scrub typhus in patients presenting with acute febrile illness in New Delhi

PurposeScrub typhus (ST) is a zoonotic disease, caused by O. tsutsugamushi is a major cause of acute febrile illness (AFI) in India. There is a need to study the prevalence and risk factors in various regions of India.MethodsA study to estimate the prevalence and study the risk factors of ST in patients presenting with acute febrile illness (AFI) was performed. All patients underwent serology for IgM antibodies to Orientia tsutsugamushi (In Bios International Inc, Seattle, WA) as per the manufacturers’ protocol. Following this, Polymerase Chain reaction (PCR) (real time SYBR green based targeting groEL gene and conventional PCR targeting 56 ?kDa type specific antigen gene) was performed from stored serum samples.ResultsDuring the study period, 473 patients were admitted. Of these 56 (11.8%) patients were ST positive by IgM serology. The conventional PCR targeting 56 ?kDa type specific antigen gene of O. tsutsugamushi was positive in six patients while Ot groEL SYBR green based PCR) was positive in five. PCR was positive in patients who had demonstrated a higher OD value in ELISA. Conventional PCR positive amplicons were sent for Sanger sequencing and confirmed to be O. tsutsugamushi. The mean age of the patients was 49 ?± ?18.3 years and males constituted a higher number of patients (67.9%, n ?= ?38). The pathognomonic eschar was present in 7 (12.5%) patients. Phylogenetic analysis revealed that sequences clustered close to Kato-like Hualein-20 strain and Karp-like Linh DT strains. All patients were administered doxycycline in our study. Mortality was recorded in 8.9% of the patients.ConclusionsIn patients presenting with acute febrile illness, ST should be considered as a differential diagnosis, especially in post-monsoon season. Along with serology, serum can also be used as sample for PCR in an intracellular bacterium like O. tsutsugamushi.     

新疆部分地区人群及动物感染恙虫病东方体调查

目的调查新疆部分地区人群及动物感染恙虫病东方体（Ot）情况,并对媒介昆虫进行调查。方法采用多种方法捕获可能感染Ot动物取脾,当地牧民静脉取血,从野鼠体表捕获恙螨,用试剂盒提取DNA,应用巢式PCR（nPCR）检测Ot-Sta56基因;接种昆明小白鼠进行Ot病原传代分离。结果共采取人群血液2430份,在6份血液中检测并分离到Ot;捕获动物13种5783个（只）,从5种啮齿动物（小家鼠、灰仓鼠、大砂土鼠、草原兔尾鼠、灰旱獭）、2种鸟类（麻雀、灰腹鹡鸰）的脾中检测并分离到Ot,从绵羊血液中检测到Ot。其他动物体内未检测到Ot。从野鼠体表分离恙螨5种,从博乐纤恙螨体内检测分离到Ot。基因序列分析表明,新疆地区存在恙虫病东方体的基因型以Karp型为主,可能存在Saitama型。结论新疆地区存在人群及动物感染Ot,其基因型以Karp为主,可能存在Saitama型。     

Development of a lateral-flow immunochromatographic test device for the rapid detection of difloxacin residues

In this study, a rapid competitive immunochromatographic test strip has been developed for specifically testing residues of difloxacin (DIF). 1H₁₀-2B₂, one of the three hybridoma lines that were tested and selected by enzyme linked immunosorbent assay, was used in the test strip. The monoclonal antibody has a good sensitivity with an IC₅₀ of 2.2 ng/mL to DIF, 0.24% cross-reactivity towards danofloxacin and no cross-reactivity towards other related compounds and other drugs. The calibration curve of DIF test strip presented a typical sigmoidal curve. In practice, the lower limit of detection using a strip reader was 0.5 ng/ml while 2 ng/ml by unaided visual assessment. Samples of milk were spiked at 2–8 ng/mL, presenting recoveries between 94.5 and 107%, and the coefficient of variation (CV,%) (1.6–9%). The data above suggests that the strip meets the requirements of high sensitivity, good specificity, simplicity and speed, as well as the characteristics of reproducibility and accuracy.