Abundance &amp; distribution of trombiculid mites &amp; Orientia tsutsugamushi, the vectors &amp; pathogen of scrub typhus in rodents &amp; shrews collected from Puducherry &amp; Tamil Nadu, India

Sadanandane, C; Ayyanar, Elango; Paily, K. P.; Karthikeyan, Anitha; Agatheswaran, Sundararajan; Jambulingam, Purushothaman

doi:10.4103/ijmr.ijmr_1390_15

Cited by 33 publications

(22 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Vector density is known to vary considerably depending on the season, vector species and rodent species [26, 27]. Many studies have trapped rodents in villages and found scrub typhus transmitting vectors, but have not been linked to cases of scrub typhus [10, 28, 29]. Our findings strengthen the argument that children could acquire scrub typhus close to their homes.…”

Section: Discussionsupporting

confidence: 81%

Risk factors for acquisition of scrub typhus in children admitted to a tertiary centre and its surrounding districts in South India: a case control study

et al. 2019

View full text Add to dashboard Cite

Background Scrub typhus is a mite borne zoonosis common in the tropics with no good preventive strategy. Children are also affected leading to considerable morbidity and mortality. We conducted a case control study and a vector survey to determine the risk factors for acquisition of scrub typhus. Methods A case control study with a 1:2 case control ratio was conducted over a 2 year period at a tertiary care centre and its surrounding districts in South India. Cases were children < 15 years with confirmed scrub typhus. Controls were age and locality matched community controls without fever. Demographic, environmental and behavioural risk factors were obtained in cases and controls by an interview and an environmental survey. A vector survey was also undertaken in the immediate vicinity of the cases. Results Case Control study: 101 cases and 167 controls were analysed. On multivariate analysis, significant association was observed with environmental factors such as the presence of a water body within 100 m of the house (OR 3.56(1.36,9.75); p 0.011), cooking outside the house (OR 5.61 (1.51,23.01); p 0.011), owning pets (OR 3.33(1.16,9.09); p 0.031), and the presence of bushes within 5 m of the house (OR 2.78 (1.11,7.69); p 0.033). Of the behavioural factors, the child going to school by a vehicle (OR 3.12 (2.29,8.37); p 0.006) was associated with an increased risk. Drying clothes on a clothesline showed a trend towards protection from acquiring scrub typhus (OR 0.31 (0.08, 1.08); p 0.077). Vector survey:26 rodents were trapped in as many houses. Trombiculid mites were isolated in 24 houses with 9(34.6%) being able to transmit scrub typhus. 254 trombiculid mites belonging to four species and two genera were collected. Leptotrombidium deliense, (33.5%). Schoengastiella ligula, (11.0%) of the total mite specimens collected. S. ligula always co-existed with L. deliense. The estimated Chigger index for Leptotrombidium deliense and Schoengastiella ligula was 3.27and 1.08 per animal respectively. Conclusions Our study highlights risk factors for scrub typhus, some of which may be modifiable. A clean peri-domestic environment free of vegetation, drying clothes on a clothesline and cooking indoors may decrease the risk of scrub typhus.

show abstract

Section: Discussionsupporting

confidence: 81%

Risk factors for acquisition of scrub typhus in children admitted to a tertiary centre and its surrounding districts in South India: a case control study

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Chiggers of these genera are commonly found in rodent hosts from many countries within the Tsutsugamushi Triangle (17). Furthermore, the overall chigger index determined by our study (33.3) was within the ranges of seasonal chigger indices reported from countries where scrub typhus is endemic (24,25). It is known that chigger FIG 2 Phylogenetic tree of the study strain and prototype Orientia strains.…”

Section: Discussionsupporting

confidence: 70%

Identification and Characterization of Orientia chuto in Trombiculid Chigger Mites Collected from Wild Rodents in Kenya

et al. 2018

View full text Add to dashboard Cite

We present data that concurs with the reported geographical expansion of scrub typhus outside the “Tsutsugamushi Triangle” and addition ofOrientia chutoas a second species in theOrientiagenus. Wild rodents were caught in Marigat, Baringo County, Kenya, and ectoparasites, including chiggers, were recovered. Rodent and chigger species were identified by taxonomic features. DNA was extracted from the chiggers and used to amplify and/or sequence the 47-kDa high temperature transmembrane protein (TSA47), the 56-kDa type-specific antigen (TSA56), and the 16S rRNA (rrs)Orientiagenes. The main rodent hosts identified wereAcomys wilsoni,Crocidurasp., andMastomys natalensis, which accounted for 59.2% of the total collection. Of these,A. wilsoniandM. natalensisharbored most of the chiggers that belonged to theNeotrombiculaandMicrotrombiculagenera. A pool of chiggers from one ofM. natalensiswas positive forOrientiaby TSA47 PCR, butOrientiadid not amplify with the TSA56 primers. On sequencing the 850 bp of the TSA47 gene, the closest phylogenetic relative wasO. chuto, with 97.65% sequence homology compared to 84.63 to 84.76% forO. tsutsugamushi. 16S rRNA deep sequencing also revealedO. chutoas the closest phylogenetic relative, with 99.75% sequence homology. These results and the existing immunological and molecular reports are strongly suggestive of the existence ofOrientiaspecies in Kenya.

show abstract

“…In Tropical North Queensland cases peaked from March to July, coinciding with the rainy season and the period immediately after the rains [146]. In Tamil Nadu, India, the highest incidence occurred from October to December, coinciding with peak chigger numbers, although chigger numbers did not fall greatly at other times of the year [147]. In Maharashtra, only minor seasonal variation was seen in Suncus murinus and Rattus blandfordi chigger indices, whereas Rattus rattus rufescens had lower rates overall and near absence of chiggers from April to June [148].…”

Section: Resultsmentioning

confidence: 99%

Scrub typhus ecology: a systematic review of Orientia in vectors and hosts

et al. 2019

View full text Add to dashboard Cite

Scrub typhus, caused by Orientia tsutsugamushi, is an important and neglected vector-borne zoonotic disease with an expanding known distribution. The ecology of the disease is complex and poorly understood, impairing discussion of public health interventions. To highlight what we know and the themes of our ignorance, we conducted a systematic review of all studies investigating the pathogen in vectors and non-human hosts. A total of 276 articles in 7 languages were included, with 793 study sites across 30 countries. There was no time restriction for article inclusion, with the oldest published in 1924. Seventy-six potential vector species and 234 vertebrate host species were tested, accounting for over one million trombiculid mites (‘chiggers’) and 83,000 vertebrates. The proportion of O. tsutsugamushi positivity was recorded for different categories of laboratory test and host species. Vector and host collection sites were geocoded and mapped. Ecological data associated with these sites were summarised. A further 145 articles encompassing general themes of scrub typhus ecology were reviewed. These topics range from the life-cycle to transmission, habitats, seasonality and human risks. Important gaps in our understanding are highlighted together with possible tools to begin to unravel these. Many of the data reported are highly variable and inconsistent and minimum data reporting standards are proposed. With more recent reports of human Orientia sp. infection in the Middle East and South America and enormous advances in research technology over recent decades, this comprehensive review provides a detailed summary of work investigating this pathogen in vectors and non-human hosts and updates current understanding of the complex ecology of scrub typhus. A better understanding of scrub typhus ecology has important relevance to ongoing research into improving diagnostics, developing vaccines and identifying useful public health interventions to reduce the burden of the disease.

show abstract

Abundance & distribution of trombiculid mites & Orientia tsutsugamushi, the vectors & pathogen of scrub typhus in rodents & shrews collected from Puducherry & Tamil Nadu, India

Cited by 33 publications

References 15 publications

Risk factors for acquisition of scrub typhus in children admitted to a tertiary centre and its surrounding districts in South India: a case control study

Risk factors for acquisition of scrub typhus in children admitted to a tertiary centre and its surrounding districts in South India: a case control study

Identification and Characterization of Orientia chuto in Trombiculid Chigger Mites Collected from Wild Rodents in Kenya

Scrub typhus ecology: a systematic review of Orientia in vectors and hosts

Contact Info

Product

Resources

About