Trombiculid Mites Research Articles

Distribution of Orientia tsutsugamushi in rodents and mites collected from Central India.

Orientia tsutsugamushi, the causative agent of scrub typhus, is an obligate intracytosolic bacterium transmitted among humans and small mammals by some species of larval trombiculid mites (chiggers). It has been recognized as a pathogen of major public health concern in the Asia-Pacific region. As disease is considered as a neglected, there exists a gap in our knowledge of the disease with regard to the sporadic epidemiologic data in endemic areas. The purpose of the study was to find out the vector as well as pathogen distribution in rodents present in the scrub typhus-reported areas in central India. We studied the seasonal variations of occurrence in O. tsutsugamushi in rodents and mites by molecular detection targeting the 56-kDa and 47-kDa genes. Rodent and mite samples were collected during December 2015 to July 2017. A total of 127 samples from rodents, seven pools of mites, and four pools of fleas were collected and processed for DNA isolation. Nested PCRs targeting the 56-kDa and 47-kDa surface antigen genes were performed. In addition, quantification of bacterial load was done by qPCR targeting the 47-kDa gene. During the pre-monsoon season, O. tsutsugamushi was detected in 12% and 10% samples employing the 56-kDa and 47-kDa nested PCRs, respectively, whereas, during post-monsoon season, the respective detection rates were 13.33% and 26.66%. This study predicted a bimodal pattern during the months of pre-monsoon and post-monsoon season with a peak in post-monsoon. Thus, the impact of season on the perpetuation of O. tsutsugamushi in the host was observed.

Clinical outcome and predictors of severity in scrub typhus patients at a tertiary care hospital in Chandigarh, India

Scrub typhus is an under-reported rickettsial illness caused by Orientia tsutsugamushi which is transmitted by trombiculid mites. Serious complications are not uncommon and multiorgan dysfunction may develop leading to death. Paucity of data on the clinical spectrum and determinants of aftermath may be contributing to higher mortality in the region. A prospective study was done to describe the spectrum of organ dysfunction in serologically confirmed cases of scrub typhus and document predictors of adverse outcomes. This prospective study was carried out in patients diagnosed to have scrub typhus by IgM ELISA. The clinical features, investigations and complications among survivors were statistically compared to those in the deceased. Fisher's exact test, t-test and logistic regression have been applied where appropriate. The study population comprised of 123 patients. Majority of patients (62%) had one or more organ dysfunction. Ten patients (8.1%) did not survive. Complications documented were acute kidney injury (AKI) in 35%, hepatitis in 29.2%, acute respiratory distress syndrome (ARDS) in 26%, shock in 13%, meningitis in 5.7%, disseminated intravascular coagulation (DIC) in 2.6%, pancreatitis in 2.6% and myocarditis in 1.6%. Certain clinical features, biochemical parameters and complications had statistically significant correlation with the outcome. The mean SOFA score was considerably higher in those who did not survive. Interpretation &conclusion: Patients developing hepatic dysfunction, acute kidney injury and respiratory distress should be identified early and intensively monitored. The SOFA score can be utilized to assess the severity at admission and rapidly triage the sicker patients.

Expression and purification of four truncated 56 kDa antigens from Orientia tsutsugamushi in Escherichia coli

Scrub typhus is an acute febrile illness caused by Orientia tsutsugamushi, transmitted to humans by the bite of the larva of trombiculid mites. Diagnosis of scrub typhus is normally based on the clinical presentations. However, it is difficult to differentiate scrub typhus from other acute febrile illnesses, such as dengue fever, malaria and leptospirosis due to similar symptoms. For differential diagnosis of scrub typhus from other acute febrile diseases, a rapid and reliable serological diagnosis is important. In order to produce an ELISA kit for detection of antibodies against O. tsutsugamushi in Vietnam, four truncated 56 kDa antigenic genes of O. tsutsugamushi including Karp (HT-09), Gilliam (HT-11), TA763 (HT-49), and Kato (YB-50) íolated from the most prevalent cases in Vietnam were cloned and expressed in E. coli Rosetta 1 cells. The recombinant proteins formed inclusion bodies when expressed in E. coli. The recombinant 56 kDa proteins in insoluble form were solubilized in 6M urea and were successfully purified by Ni2+affinity column. The purity of four recombinant proteins,HT-09, HT-11, HT-49 and YB-50,reached more than 95% and their concentrations are 12,57 mg/ml; 11,6 mg/ml; 8,98 mg/ml và 8,02 mg/ml, respectively.

Geometric morphometrics of the scutum for differentiation of trombiculid mites within the genus Walchia (Acariformes: Prostigmata: Trombiculidae), a probable vector of scrub typhus

The vectors of scrub typhus are the larval stage of trombiculid mites, termed “chiggers”. These vectors are very small – the larvae are approximately 0.2 mm in size - and therefore their morphological identification is difficult. Trombiculid mites are widely distributed across Asia and they can be identified at the genus level by the shape, size and setae/sensilla distribution of their dorsal chitin plate (scutum = shield), while morphological identification at the species level requires more mite characteristics.We recently developed a methodology to ascertain paired matched genotype and morphotype of individual chiggers, based on autofluorescence and brightfield microscopy with subsequent molecular identification using the COI gene (approximately 640bp length). However, based on 20 chigger specimens characterised by paired genotypic and morphological data consisting of the four species [Walchia ewingi with 2 subspecies]: Walchia ewingi lupella (n = 9), W. ewingi ewingi (n = 2), W. alpestris (n = 2), W. kritochaeta (n = 5) and W. minuscuta (n = 2) we found evidence of genetic polymorphism and morphological plasticity within the genus Walchia. The phylogenetic inference of the intra-genus relationships within the Walchia spp., based on COI gene (Blankaartia spp. served as outgroup), delineated the five included species by an average interspecific divergence of mean distance 0.218 (0.126 – 0.323).We therefore applied landmark-based and outline-based geometric morphometric (GM) approaches to differentiate Walchia species using scutum measurements. A total of 261 scutum images of Walchia spp. were examined by landmark-based GM (140 chigger specimens) and outline-based GM (121 specimens) techniques. All Walchia spp. showed significant differences in scutum size and shape. W. minuscuta showed the smallest mean scutum size in both techniques. The largest scutum was found in W. ewingi lupella and W. ewingi ewingi by landmark-based and outline-based GM analysis, respectively. The scutum shapes of W. alpestris and W. minuscuta were clearly distinguished from the other species. Cross-validated classification scores were different depending on species and digitizing techniques and landmark-based GM showed better scores than outline-based GM. We conclude that the morphologically closely-related trombiculid mite species can be further differentiated by their scutum features alone, using GM approaches. This technique is a promising tool for the much-needed characterization studies of chiggers and needs evaluation using matched morphometric and genotyping data for other genera of trombiculids.

Hierarchical Bayesian modeling of spatio-temporal patterns of scrub typhus incidence for 2009–2013 in South Korea

This study aims to analyze spatio-temporal patterns of scrub typhus incidence and to identify environmental risk factors in South Korea from 2009 to 2013 using hierarchical Bayesian Poisson model. We classified 244 municipal areas into nine categories based on the posterior relative risks and their temporal trends and these patterns were visualized. Environmental covariates (i.e. land surface temperature, precipitation and vegetation) were compiled by season to reflect the seasonal behavior of trombiculid mites and rodents and by year to explain year-based environmental changes. A total of six covariates were incorporated in the regression model and environmental effects were evaluated. We found areas in the south, southwest, and southeast of South Korea that present relatively high risk, and the north and southeast parts show rapid increases during the study period. The spatio-temporal maps present similar patterns as well. A positive correlation is found between the scrub typhus risk and precipitation in summer, and normalized difference vegetation index in fall. In contrast, the scrub typhus risk is negatively correlated with land surface temperature in fall. This information has implications for prioritizing disease control resources on high-risk areas. Furthermore, the regression results might be utilized for predicting scrub typhus incidence and contribute to the design of disease control programs in the future.

Occurrence of Orientia tsutsugamushi, the Etiological Agent of Scrub Typhus in Animal Hosts and Mite Vectors in Areas Reporting Human Cases of Acute Encephalitis Syndrome in the Gorakhpur Region of Uttar Pradesh, India.

Outbreaks of acute encephalitis syndrome (AES) with high fatality and disability, are reported every year in the Gorakhpur region of Uttar Pradesh, India, with the etiology of >60% of the cases being attributed to scrub typhus. In the present study, the prevalence of Orientia tsutsugamushi, the etiological agent of scrub typhus, was investigated among animal hosts and their ectoparasitic trombiculid mites prevalent in AES-reported areas of Gorakhpur. A total of 154 rodents/shrews were collected using 777 Sherman traps set in 12 study villages, and the overall trap rate was 19.8%. In total, 2726 trombiculid mites belonging to 12 species were collected from 154 rodents/shrews trapped. The shrew mouse Suncus murinus was the predominant animal species (78.6%) collected. The principal vector mite Leptotrombidium deliense was the predominant species (82.7%), and its index was 14.6 per animal. Of 114 rodent/shrew sera samples screened through the Weil-Felix test, 57% were positive for antibodies against O. tsutsugamushi. Of 128 blood samples tested by polymerase chain reaction (PCR), one rodent sample was positive for the gene encoding 56 kDa protein and 25 for 60 kDa. Among 2726 mite samples tested as 315 pools through nested PCR, seven pools were positive for 56 kDa gene. Phylogenetic analysis confirmed circulation of Gilliam, Karp, and TA678 serotypes of O. tsutsugamushi in Gorakhpur. The study clearly demonstrated natural infection of O. tsutsugamushi in both small-animal hosts and vector mites in the AES-reporting villages of Gorakhpur, which confirms transmission of the scrub typhus pathogen in this region. The high infestation rate of L. deliense with O. tsutsugamushi infection indicates that the people living in the rural villages of Gorakhpur are at risk of infection with scrub typhus, which might lead to AES.

Heterogeneity of Orientia tsutsugamushi genotypes in field-collected trombiculid mites from wild-caught small mammals in Thailand.

Trombiculid mites are the vectors of scrub typhus, with infected larval mites (chiggers) transmitting the causative agent, Orientia tsutsugamushi, during feeding. Co-existence of multiple O. tsutsugamushi strains within infected mites has previously been reported in naturally infected, laboratory-reared mite lines using molecular methods to characterize the 56-kDa type-specific antigen (TSA) gene. In the current study, more advanced next-generation sequencing technology was used to reveal the heterogeneity of O. tsutsugamushi genotypes in field-collected trombiculid mites from rodents and small mammals in scrub typhus-endemic areas of Thailand. Twenty-eight trombiculid mites collected from 10 small mammals were positive for O. tsutsugamushi, corresponding to a prevalence rate of 0.7% within the mite population. Twenty-four of the infected mites were Leptotrombidium spp., indicating that this genus is the main vector for O. tsutsugamushi transmission in Thailand. In addition, O. tsutsugamushi was detected in the mite genera Ascoschoengastia, Blankaartia, Gahrliepia, and Lorillatum. Of the 10 infested small animal hosts, six had 2–10 infected mites feeding at the time of collection. Deep sequencing was used to characterize mixed infections (two to three O. tsutsugamushi genotypes within an individual mite), and 5 of the 28 infected mites (17.9%) contained mixed infections. Additionally, 56-kDa TSA gene sequence analysis revealed identical bacterial genotypes among co-feeding mites with single or mixed infections. These results suggest that co-feeding transmission may occur during the feeding process, and could explain the occurrence of mixed infections in individual mites, as well as the recovery of multiple infected mites from the same host. This study also revealed highly diverse within-host O. tsutsugamushi genotypes. The occurrence of multiple O. tsutsugamushi genotypes within individual mites has important implications, and could provide a mechanism for pathogen evolution/diversification in the mite vector.

The saga of scrub typhus with a note on the outbreaks in Mizoram

Scrub typhus is one the most important re-emerging infectious disease, and perhaps, the most important bacterial disease. Caused by Orientia tsutsugamushi, it is transmitted through the bite of mites belonging to the genus Leptotrombidium, in which the bacteria are obligate parasites. Though the mites are natural ectoparasites of rodents and other animals, in which there is no disease, opportunistic infection to humans gives rise to a serious disease. Known to Japanese physicians as tsutsugamushi (insect disease), human infection is caused by the larvae of trombiculid mites, the fact established by Mataro Nagayo and co-workers established in 1917. The pathogen was discovered by Naosuke Hayashi in 1920. In Mizoram, the disease has been rampant since 2011. This paper summarises available data on the prevalence of the infection in different districts base on collective information from various sources. Records between 2012 and 2018 show that over a thousand people had been infected and 35 people had died of the disease.

Autofluorescence microscopy for paired-matched morphological and molecular identification of individual chigger mites (Acari: Trombiculidae), the vectors of scrub typhus.

BackgroundConventional gold standard characterization of chigger mites involves chemical preparation procedures (i.e. specimen clearing) for visualization of morphological features, which however contributes to destruction of the arthropod host DNA and any endosymbiont or pathogen DNA harbored within the specimen.Methodology/Principal findingsIn this study, a novel work flow based on autofluorescence microscopy was developed to enable identification of trombiculid mites to the species level on the basis of morphological traits without any special preparation, while preserving the mite DNA for subsequent genotyping. A panel of 16 specifically selected fluorescence microscopy images of mite features from available identification keys served for complete chigger morphological identification to the species level, and was paired with corresponding genotype data. We evaluated and validated this method for paired chigger morphological and genotypic ID using the mitochondrial cytochrome c oxidase subunit I gene (coi) in 113 chigger specimens representing 12 species and 7 genera (Leptotrombidium, Ascoschoengastia, Gahrliepia, Walchia, Blankaartia, Schoengastia and Schoutedenichia) from the Lao People’s Democratic Republic (Lao PDR) to the species level (complete characterization), and 153 chiggers from 5 genera (Leptotrombidium, Ascoschoengastia, Helenicula, Schoengastiella and Walchia) from Thailand, Cambodia and Lao PDR to the genus level.A phylogenetic tree constructed from 77 coi gene sequences (approximately 640 bp length, n = 52 new coi sequences and n = 25 downloaded from GenBank), demonstrated clear grouping of assigned morphotypes at the genus levels, although evidence of both genetic polymorphism and morphological plasticity was found.Conclusions/SignificanceWith this new methodology, we provided the largest collection of characterized coi gene sequences for trombiculid mites to date, and almost doubled the number of available characterized coi gene sequences with a single study. The ability to provide paired phenotypic-genotypic data is of central importance for future characterization of mites and dissecting the molecular epidemiology of mites transmitting diseases like scrub typhus.

Scrub typhus: a case report

Scrub typhus is a rare rickettsial disease which is endemic in the state of Himachal Pradesh. It is caused by bacteria called Orentia tsutsugumasi and transmitted by larvae of Trombiculid mites. Though rarely seen in the plains, it should be kept as differential for a patient presenting as fever with seizure. Eschar may or may not be seen in all cases. We report a case of scrub typhus in a patient who presented with fever and seizures but no eschar.

Scrub typhus, an emerging infectious disease in Chile

Scrub typhus, caused by Orientia tsutsugamushi and transmitted by larvae of trombiculid mites, is an endemic rickettsiosis in the Asia Pacific region. After the first identification of a case in Chile in 2006, more than 30 cases have been diagnosed by our group since 2015. Cases were detected predominantly during the Chilean summer months. Patients presented with fever, rash, and a typical eschar at the inoculation site; other frequent findings were intense headache, night sweats, increased laboratory markers of inflammation and transaminases. The vast majority of cases have been diagnosed in southern Chile (mainly Chiloé Island), although recently some cases were also identified in the central Metropolitan Region in patients returning from trips to southern Chile. Physicians attending Chilean patients should be aware of this emerging infection to be able to initiate empirical therapy with doxycycline. The confirmation of cases by the diagnostic methods available in Chile will contribute to a better understanding of the epidemiological and clinical relevance of this emerging infection in South America.

Disease forecasting model for newly emerging bacterial seed and boll rot of cotton disease and its vector (Dysdercus cingulatus)

Bacterial seed and boll rot disease is a newly emerging threat to the cotton growers. Disease prediction model was devised to predict the disease progression impacted by the vector (Dysdercus cingulatus) and environmental variables (maximum air temperature, minimum air temperature, relative humidity and rainfall) on four varieties to minimise its losses and disease management cost. Impact of a-biotic environmental variables (maximum and minimum air temperature, relative humidity and rainfall) was assessed on bacterial seed and rot of cotton disease and its vector (D. cingulatus) on FH-941, FH-942, MNH-886 and FH-114 cotton varieties. Maximum red cotton bug population was assessed at 29–31 °C maximum temperature and at 15–17 °C minimum temperature. Disease severity was noticed maximum when maximum and minimum temperature was measured at 28–29 °C and 13–14.5 °C, respectively. Vector population was maximum when relative humidity and rainfall were 63–66% and 1.50–2.5 mm, respectively. Relative humidity at 66–68% and 0.5–1.5 mm rainfall favoured disease development. With increase in number of bugs, increase in disease severity was noted, maximum disease severity 45–48% noticed when 7–8 bugs were recorded. Red cotton bug (Dysdercus cingulatus) population prediction model was devised based on a-biotic factors (maximum and minimum air temperature, relative humidity and rainfall) on four cotton varieties. Disease forecasting model was developed based on biotic (D. cingulatus) and a-biotic factors. A close resemblance between observed and the predicted red cotton bugs and disease severity was seen.

Prevalence and Phylogenetic Analysis ofOrientia tsutsugamushiin Rodents and Mites from Central India

Orientia tsutsugamushi, the causative agent of scrub typhus in humans, is an obligate intracytosolic bacterium transmitted among animals and to humans by some species of larval trombiculid mites (chiggers) and is hosted mainly by rodents. In this study, we attempted detection of O. tsutsugamushi from blood and tissue samples of rodents trapped from different locations in Central India using PCR targeting the 56 kDa outer membrane protein gene and the 47 kDa high temperature transmembrane protein gene. A total of 59 rodent samples comprising 38 of blood collected from domestic and public surroundings and 21 of tissue from agricultural farm were included in this study. The 56 kDa outer membrane protein gene was detected from 10 of 59 samples by PCR, and the 47 kDa protein gene was detected from 4 of 59 samples by nested-PCR. Mites collected from the rodents were identified as Ornithonyssus bacoti, and one of five pooled samples was found to be positive for O. tsutsugamushi using PCR targeting 56 kDa outer membrane protein gene. Thus, perpetuation of O. tsutsugamushi among rodents and mites was detected constituting a potential public health concern.

Hemipteroseius vikrami Menon: a junior synonym of H. indicus (Krantz & Khot) (Acari: Otopheidomenidae) with comments on the sigilla of the dorsal shield

Hemipteroseius vikrami Menon, 2011 (Acari: Otopheidomenidae: Treatinae) has been considered a junior synonym of Hemipteroseius indicus (Krantz & Khot, 1962). Both species were described from India from the red cotton bugs Dysdercus koenigii (F.) and Dysdercus cingulatus (F.), the latter is widely distributed in India and some other countries. The sigilla of the podonotum and opisthonotum are also described for the first time in this mite.

Evaluation of two diagnostic methods of scrub typhus with Bayes rule

Background: Scrub typhus or rickettsia, a zoonotic infection occurs due to the transmission of Gram-negative bacteria, Orientia tsutsugamushi and/or Tsutsugamushi sp. by the larval stage of the trombiculid mite, Leptotrombidium deliense. Infections at endothelial cells and phagocytes manifest clinically as vasculitis with an acute onset of fever, rashes, headache, myalgia, multiple organ dysfunction, eschar, respiratory morbidity, meningioencephalitis and sepsis syndrome on skin, whose severity varying with patients. Herein obtained data is used for evaluating the dependability of two determinative tests.Methods: The prospective survey with 80 rickettsia patients was carried during the last 6 months of 2016. Patients with the occurrence of fever for more than two days and a clinical suspicion of rickettsia infection were promoted for Weil-Felix as well as, ELISA tests.Results: The prevalence of rickettsia in the population of 80 patients was 17.5, and the sensitivity (the portion of the people with the rickettsia infection who will have positive Weil-Felix test results) value was 0.7143 and specificity (the people without the disease who will have negative Weil-Felix test results) value was 0.9697. Probability of Weil Felix test positive was 0.15, and probability of ELISA test positive was 0.175.Conclusions: The dependability of each test independently or a posteriori probability was 0.857. Both tests are dependable for correctness of outcomes being 0.857 or 85.7%, in combination; a high specificity value of Weil Felix test is a valuable test.

Murine models of scrub typhus associated with host control of Orientia tsutsugamushi infection.

BackgroundScrub typhus, a febrile illness of substantial incidence and mortality, is caused by infection with the obligately intracellular bacterium Orientia tsutsugamushi. It is estimated that there are more than one million cases annually transmitted by the parasitic larval stage of trombiculid mites in the Asia-Pacific region. The antigenic and genetic diversity of the multiple strains of O. tsutsugamushi hinders the advancement of laboratory diagnosis, development of long-lasting vaccine-induced protection, and interpretation of clinical infection. Despite the life-threatening severity of the illness in hundreds of thousands of cases annually, 85–93% of patients survive, often without anti-rickettsial treatment. To more completely understand the disease caused by Orientia infection, animal models which closely correlate with the clinical manifestations, target cells, organ involvement, and histopathologic lesions of human cases of scrub typhus should be employed. Previously, our laboratory has extensively characterized two relevant C57BL/6 mouse models using O. tsutsugamushi Karp strain: a route-specific intradermal model of infection and persistence and a hematogenously disseminated dose-dependent lethal model.Principal findingsTo complement the lethal model, here we illustrate a sublethal model in the same mouse strain using the O. tsutsugamushi Gilliam strain, which resulted in dose-dependent severity of illness, weight loss, and systemic dissemination to endothelial cells of the microcirculation and mononuclear phagocytic cells. Histopathologic lesions included expansion of the pulmonary interstitium by inflammatory cell infiltrates and multifocal hepatic lesions with mononuclear cellular infiltrates, renal interstitial lymphohistiocytic inflammation, mild meningoencephalitis, and characteristic typhus nodules.SignificanceThese models parallel characteristics of human cases of scrub typhus, and will be used in concert to understand differences in severity which lead to lethality or host control of the infection and to address the explanation for short duration of heterologous immunity in Orientia infection.

Meteorological factors affect the epidemiology of hemorrhagic fever with renal syndrome via altering the breeding and hantavirus-carrying states of rodents and mites: a 9 years’ longitudinal study

The incidence of hemorrhagic fever with renal syndrome (HFRS) in Qingdao, China was three times higher than that of the average national level. Here we characterized the epidemiology, ecological determinants and pathogen evolution of HFRS in Qingdao during 2007–2015. In this longitudinal study, a total of 1846 HFRS patients and 41 HFRS-related deaths were reported. HFRS in Qingdao peaked once a year in the fourth quarter. We built a time series generalized additive model, and found that meteorological factors in the previous quarter could accurately predict HFRS occurrence. To explore how meteorological factors influenced the epidemic of HFRS, we analyzed the relationship between meteorological factors and hantavirus-carrying states of the hosts (including rodents and shrews). Comprehensive analysis showed humidity was correlated to high host densities in the third quarter and high hantavirus-carrying rates of animal hosts in the third to fourth quarters, which might contribute to HFRS peak in the fourth quarter. We further compared the L segments of hantaviruses from HFRS patients, animal hosts and ectoparasites. Phylogenetic analysis showed that hantaviruses in gamasid and trombiculid mites were the same as those from the hosts. This indicated mites also contributed to the transmission of hantavirus. Furthermore, Hantaan virus from HFRS patients, hosts and mites in Qingdao formed a distinct phylogenetic cluster. A new clade of Seoul virus was also identified in the hosts. Overall, meteorological factors increase HFRS incidence possibly via facilitating hosts’ reproduction and consequent mite-mediated hantavirus transmission. New hantavirus subtypes evolved in Qingdao represent new challenges of fighting against HFRS.Emerging Microbes & Infections (2017) 6, e104; doi:10.1038/emi.2017.92; published online 29 November 2017

Zoonotic surveillance for rickettsiae in rodents and mapping of vectors of rickettsial diseases in India: A multi-centric study.

The global resurgence of rickettsial diseases and their potential to impact the fitness of military personnel and inflict widespread casualties amongst civil populations has emerged as a major cause of public health concern. Absence of surveillance system, lack of awareness amongst medical fraternity to rickettsial activity along with the difficulty in diagnosis because of their protean clinical manifestations are reasons for the outbreaks of these diseases. To determine rickettsial activity amongst rodents and study vector diversity, abundance and their distribution to enable mapping of rickettsial hotspots. Zoonotic surveillance was undertaken in six selected study areas in India - Jammu, Akhnoor, Rajouri-Poonch, Udhampur-Nagrota, Dehradun and Pune. Weil-Felix test was used for rickettsial sero-surveillance amongst rodents and standard identification keys were used for mapping vector diversity and database preparation. Serological findings revealed positivity to all the three rickettsial antigens (OXK, OX19 and OX2) in Jammu, OX19 in Dehradun and OXK and OX2 positivity in Udhampur-Nagrota belt. The vector database records presence of 16 species of trombiculid mites from three important genera - Leptotrombidium, Schoengastiella and Gahrliepia with ticks from five genera and 8 species of fleas from four genera. Mite fauna of study sites has been enriched with addition of new records of mite species (five mite species at Pune, two at Akhnoor with one mite species each at Jammu and Dehradun). The study reveals rickettsial activity amongst rodents at Jammu, Dehradun and Udhampur-Nagrota belt. The results correlate well with the presence of vectors of scrub and tick typhus and corroborate the occurrence of outbreaks of these diseases in the respective areas.

Scrub typhus in children

Scrub typhus is a mite-borne acute febrile illness caused by Orientia tsutsugamushi, and is transmitted by the bite of the trombiculid mite. It presents with high-grade fever which may be associated with nonspecific signs and symptoms such as rash, muscle and abdominal pain, headache, and lymph node enlargement. Scrub typhus is, therefore, one of the differential diagnoses to be considered in a child with acute undifferentiated febrile illness, especially if the disease is endemic to the region. The presence of a painless eschar at the site of the bite is an important pointer to the diagnosis. The illness responds well to antibiotics, usually within 48 h.

Scrub typhus

Scrub typhus is an important emerging tropical infection that can have severe manifestations in children leading to intensive care admission. It is caused by Orientia tsutsugamushi, a gram negative bacterium transmitted to humans by the bite of larval trombiculid mites. The organism is endemic in south-east Asia and the disease is reported from virtually all parts of India. The hallmark of this infection is vasculitis and endothelial injury with intense inflammatory response involving myocardium, pulmonary, nervous and hematological systems. Children present often in post-monsoon season with undifferentiated fever and various degrees of organ involvement that progress to fatal multi organ failure if untreated. Presence of an eschar can be a vital diagnostic clue. Common laboratory features include thrombocytopenia, elevated transaminases and hypoalbuminemia. The diagnosis is confirmed by detection of IgM antibodies by IFA and ELISA or by PCR based assays. Definitive treatment with doxycycline or azithromycin and aggressive supportive care including ventilation, hemodynamic support, and management of AKI and raised intracranial pressure are the mainstay. The mortality ranges from 6-15%, which currently on the improving trend due to better case identification and early initiation of antibiotics along with intensive care.