Tags

Type your tag names separated by a space and hit enter

Orientia tsutsugamushi dynamics in vectors and hosts: ecology and risk factors for foci of scrub typhus transmission in northern Thailand.
Parasit Vectors. 2021 Oct 18; 14(1):540.PV

Abstract

BACKGROUND

Scrub typhus is an important neglected vector-borne zoonotic disease across the Asia-Pacific region, with an expanding known distribution. The disease ecology is poorly understood, despite the large global burden of disease. The key determinants of high-risk areas of transmission to humans are unknown.

METHODS

Small mammals and chiggers were collected over an 18-month period at three sites of differing ecological profiles with high scrub typhus transmission in Chiang Rai Province, northern Thailand. Field samples were identified and tested for Orientia tsutsugamushi by real-time PCR. The rates and dynamics of infection were recorded, and positive and negative individuals were mapped over time at the scale of single villages. Ecological analyses were performed to describe the species richness, community structure and interactions between infected and uninfected species and habitats. Generalised linear modelling (GLM) was applied to examine these interactions.

RESULTS

The site with the highest rates of human infection was associated with the highest number of infected chigger pools (41%), individual chiggers (16%), proportion of the known vector species Leptotrombidium deliense (71%) and chigger index (151). Chigger species diversity was lowest (Shannon diversity index H': 1.77) and rodent density appeared to be high. There were no consistent discrete foci of infection identified at any of the study sites. The small mammals Rattus tanezumi and Bandicota indica and the chiggers L. deliense and Walchia kritochaeta emerged as central nodes in the network analysis. In the GLM, the end of the dry season, and to a lesser extent the end of the wet season, was associated with O. tsutsugamushi-infected small mammals and chiggers. A clear positive association was seen between O. tsutsugamushi-positive chigger pools and the combination of O. tsutsugamushi-positive chigger pools and O. tsutsugamushi-positive small mammals with lowland habitats.

CONCLUSIONS

These findings begin to reveal some of the factors that may determine high-risk foci of scrub typhus at a fine local scale. Understanding these factors may allow practical public health interventions to reduce disease risk. Further studies are needed in areas with diverse ecology.

Links

PMC Free PDF

Authors+Show Affiliations

Elliott I
Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit, Microbiology Laboratory, Mahosot Hospital, Vientiane, Lao PDR. ivo.elliott@ndm.ox.ac.uk. Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK. ivo.elliott@ndm.ox.ac.uk.
Thangnimitchok N
Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit, Microbiology Laboratory, Mahosot Hospital, Vientiane, Lao PDR.
Chaisiri K
Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Wangrangsimakul T
Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK. Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Jaiboon P
Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Day NPJ
Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK. Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Paris DH
Department of Medicine, Swiss Tropical and Public Health Institute, Basel, Switzerland. Department of Clinical Research, University of Basel, Basel, Switzerland.
Newton PN
Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit, Microbiology Laboratory, Mahosot Hospital, Vientiane, Lao PDR. Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK. Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Morand S
CNRS ISEM-CIRAD ASTRE, Faculty of Veterinary Technology, Kasetsart University, Bangkok, Thailand.

MeSH

AnimalsDisease VectorsEcological and Environmental PhenomenaHumansMammalsMite InfestationsOrientia tsutsugamushiRatsRisk FactorsRodentiaScrub TyphusThailandTrombiculidaeZoonoses

Pub Type(s)

Journal Article

Language

eng

PubMed ID

34663445

Citation

Elliott, Ivo, et al. "Orientia Tsutsugamushi Dynamics in Vectors and Hosts: Ecology and Risk Factors for Foci of Scrub Typhus Transmission in Northern Thailand." Parasites & Vectors, vol. 14, no. 1, 2021, p. 540.
Elliott I, Thangnimitchok N, Chaisiri K, et al. Orientia tsutsugamushi dynamics in vectors and hosts: ecology and risk factors for foci of scrub typhus transmission in northern Thailand. Parasit Vectors. 2021;14(1):540.
Elliott, I., Thangnimitchok, N., Chaisiri, K., Wangrangsimakul, T., Jaiboon, P., Day, N. P. J., Paris, D. H., Newton, P. N., & Morand, S. (2021). Orientia tsutsugamushi dynamics in vectors and hosts: ecology and risk factors for foci of scrub typhus transmission in northern Thailand. Parasites & Vectors, 14(1), 540. https://doi.org/10.1186/s13071-021-05042-4
Elliott I, et al. Orientia Tsutsugamushi Dynamics in Vectors and Hosts: Ecology and Risk Factors for Foci of Scrub Typhus Transmission in Northern Thailand. Parasit Vectors. 2021 Oct 18;14(1):540. PubMed PMID: 34663445.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Orientia tsutsugamushi dynamics in vectors and hosts: ecology and risk factors for foci of scrub typhus transmission in northern Thailand. AU - Elliott,Ivo, AU - Thangnimitchok,Neeranuch, AU - Chaisiri,Kittipong, AU - Wangrangsimakul,Tri, AU - Jaiboon,Piangnet, AU - Day,Nicholas P J, AU - Paris,Daniel H, AU - Newton,Paul N, AU - Morand,Serge, Y1 - 2021/10/18/ PY - 2021/07/10/received PY - 2021/09/27/accepted PY - 2021/10/19/entrez PY - 2021/10/20/pubmed PY - 2022/1/8/medline KW - Chigger KW - Ecology KW - Orientia tsutsugamushi KW - Scrub typhus KW - Thailand SP - 540 EP - 540 JF - Parasites & vectors JO - Parasit Vectors VL - 14 IS - 1 N2 - BACKGROUND: Scrub typhus is an important neglected vector-borne zoonotic disease across the Asia-Pacific region, with an expanding known distribution. The disease ecology is poorly understood, despite the large global burden of disease. The key determinants of high-risk areas of transmission to humans are unknown. METHODS: Small mammals and chiggers were collected over an 18-month period at three sites of differing ecological profiles with high scrub typhus transmission in Chiang Rai Province, northern Thailand. Field samples were identified and tested for Orientia tsutsugamushi by real-time PCR. The rates and dynamics of infection were recorded, and positive and negative individuals were mapped over time at the scale of single villages. Ecological analyses were performed to describe the species richness, community structure and interactions between infected and uninfected species and habitats. Generalised linear modelling (GLM) was applied to examine these interactions. RESULTS: The site with the highest rates of human infection was associated with the highest number of infected chigger pools (41%), individual chiggers (16%), proportion of the known vector species Leptotrombidium deliense (71%) and chigger index (151). Chigger species diversity was lowest (Shannon diversity index H': 1.77) and rodent density appeared to be high. There were no consistent discrete foci of infection identified at any of the study sites. The small mammals Rattus tanezumi and Bandicota indica and the chiggers L. deliense and Walchia kritochaeta emerged as central nodes in the network analysis. In the GLM, the end of the dry season, and to a lesser extent the end of the wet season, was associated with O. tsutsugamushi-infected small mammals and chiggers. A clear positive association was seen between O. tsutsugamushi-positive chigger pools and the combination of O. tsutsugamushi-positive chigger pools and O. tsutsugamushi-positive small mammals with lowland habitats. CONCLUSIONS: These findings begin to reveal some of the factors that may determine high-risk foci of scrub typhus at a fine local scale. Understanding these factors may allow practical public health interventions to reduce disease risk. Further studies are needed in areas with diverse ecology. SN - 1756-3305 UR - https://www.unboundmedicine.com/medline/citation/34663445/Orientia_tsutsugamushi_dynamics_in_vectors_and_hosts:_ecology_and_risk_factors_for_foci_of_scrub_typhus_transmission_in_northern_Thailand_ DB - PRIME DP - Unbound Medicine ER -