1. Orientia tsutsugamushi dynamics in vectors and hosts: ecology and risk factors for foci of scrub typhus transmission in northern Thailand
- Author
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Serge Morand, Neeranuch Thangnimitchok, Paul N. Newton, Tri Wangrangsimakul, Nicholas P. J. Day, Kittipong Chaisiri, Daniel H. Paris, Piangnet Jaiboon, Ivo Elliott, Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit (LOMWRU), Mahidol University [Bangkok]-Mahosot Hospital, Centre for Tropical Medicine and Global Health [Oxford, UK], Nuffield Department of Medicine [Oxford, UK] (Big Data Institute), University of Oxford [Oxford]-University of Oxford [Oxford], Department of Clinical Tropical Medicine [Bangkok, Thailand] (Faculty of Tropical Medicine), Mahidol University [Bangkok], Mahidol Oxford Tropical Medicine Research Unit (MORU), Wellcome Trust-Mahidol University [Bangkok]-University of Oxford [Oxford], University of Basel (Unibas), Swiss Tropical and Public Health Institute [Basel], Animal, Santé, Territoires, Risques et Ecosystèmes (UMR ASTRE), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Kasetsart University - KU (THAILAND), Kasetsart University (KU), This research was funded in whole, or in part, by the Wellcome Trust (105731/Z/14/Z). SM was supported by the French ANR FutureHealthSEA ANR17-CE35-0003-01., and ANR-17-CE35-0003,FutureHealthSEA,Scénarios de la santé en Asie du Sud-Est: changements d'utilisation des terres, changement climatique et maladies infectieuses(2017)
- Subjects
Mite Infestations ,Orientia tsutsugamushi ,[SDV]Life Sciences [q-bio] ,030231 tropical medicine ,Ecological and Environmental Phenomena ,Rodentia ,Infectious and parasitic diseases ,RC109-216 ,Trombiculidae ,Scrub typhus ,Disease Vectors ,03 medical and health sciences ,Diversity index ,0302 clinical medicine ,Risk Factors ,Zoonoses ,Leptotrombidium deliense ,medicine ,Animals ,Humans ,030304 developmental biology ,Mammals ,0303 health sciences ,Ecology ,biology ,Research ,Bandicota indica ,Species diversity ,Chigger ,15. Life on land ,bacterial infections and mycoses ,Thailand ,biology.organism_classification ,medicine.disease ,Rats ,3. Good health ,Infectious Diseases ,Scrub Typhus ,Vector (epidemiology) ,Parasitology ,Species richness - 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. Graphical abstract
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- 2022