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Surveillance of potential hosts and vectors of scrub typhus in Taiwan.
Parasit Vectors 2015; 8:611PV

Abstract

BACKGROUND

Scrub typhus is a lethal infectious disease vectored by larval trombiculid mites (i.e. chiggers) infected with Orientia tsutsugamushi (OT) and recent decades have witnessed an emergence of scrub typhus in several countries. Identification of chigger species and their vertebrate hosts is fundamental for the assessment of human risks to scrub typhus under environmental changes, but intensive and extensive survey of chiggers and their hosts is still lacking in Taiwan.

METHODS

Chiggers were collected from shrews and rodents in nine counties of Taiwan and were assayed for OT infections with nested polymerase chain reaction (PCR). PCR products were further sequenced to reveal probable OT strains. Rodents were assessed for OT exposure by immunofluorescent antibody assay. Lastly, incidence rate of scrub typhus in each county was associated with loads and prevalence of chigger infestations, seropositivity rate in rodents, and OT positivity rate in chiggers.

RESULTS

Rattus losea was the most abundant (48.7% of 1,285 individuals) and widespread (occurred in nine counties) small mammal species and hosted the majority of chiggers (76.4% of 128,520 chiggers). Leptotrombidium deliense was the most common (64.9% of all identified chiggers) and widespread (occurred in seven counties) chigger species but was replaced by Leptotrombidium pallidum or Leptotrombidium scutellare during the cold seasons in two counties (Matsu and Kinmen) where winter temperatures were lower than other study sites. Seropositivity rate for OT exposure in 876 assayed rodents was 43.0% and OT positivity rate in 347 pools of chiggers was 55.9%, with 15 OT strains identified in the 107 successfully sequenced samples. Incidence rate of scrub typhus was positively correlated with chigger loads, prevalence of chigger infestations, seropositivity rate but not OT positivity rate in chiggers.

CONCLUSIONS

Our study reveals R. losea as the primary host for chiggers and there exists a geographical and seasonal variation in chigger species in Taiwan. It also emphasizes the importance of recognition of chigger vectors and their vertebrate hosts for a better prediction of human risks to scrub typhus under rapid environmental changes.

Authors+Show Affiliations

Department of Life Science, National Taiwan Normal University, Taipei, Taiwan. cckuo@ntnu.edu.tw.Center for Research, Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taipei, No. 161, Kun-Yang Street, Taipei, 11561, Taiwan. leepl@ntu.edu.tw.Center for Research, Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taipei, No. 161, Kun-Yang Street, Taipei, 11561, Taiwan. hc0257@mail.hcbaphiq.gov.tw.Center for Research, Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taipei, No. 161, Kun-Yang Street, Taipei, 11561, Taiwan. sjwang@cdc.gov.tw.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

26626287

Citation

Kuo, Chi-Chien, et al. "Surveillance of Potential Hosts and Vectors of Scrub Typhus in Taiwan." Parasites & Vectors, vol. 8, 2015, p. 611.
Kuo CC, Lee PL, Chen CH, et al. Surveillance of potential hosts and vectors of scrub typhus in Taiwan. Parasit Vectors. 2015;8:611.
Kuo, C. C., Lee, P. L., Chen, C. H., & Wang, H. C. (2015). Surveillance of potential hosts and vectors of scrub typhus in Taiwan. Parasites & Vectors, 8, p. 611. doi:10.1186/s13071-015-1221-7.
Kuo CC, et al. Surveillance of Potential Hosts and Vectors of Scrub Typhus in Taiwan. Parasit Vectors. 2015 Dec 1;8:611. PubMed PMID: 26626287.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Surveillance of potential hosts and vectors of scrub typhus in Taiwan. AU - Kuo,Chi-Chien, AU - Lee,Pei-Lung, AU - Chen,Chun-Hsung, AU - Wang,Hsi-Chieh, Y1 - 2015/12/01/ PY - 2015/08/31/received PY - 2015/11/21/accepted PY - 2015/12/3/entrez PY - 2015/12/3/pubmed PY - 2016/7/23/medline SP - 611 EP - 611 JF - Parasites & vectors JO - Parasit Vectors VL - 8 N2 - BACKGROUND: Scrub typhus is a lethal infectious disease vectored by larval trombiculid mites (i.e. chiggers) infected with Orientia tsutsugamushi (OT) and recent decades have witnessed an emergence of scrub typhus in several countries. Identification of chigger species and their vertebrate hosts is fundamental for the assessment of human risks to scrub typhus under environmental changes, but intensive and extensive survey of chiggers and their hosts is still lacking in Taiwan. METHODS: Chiggers were collected from shrews and rodents in nine counties of Taiwan and were assayed for OT infections with nested polymerase chain reaction (PCR). PCR products were further sequenced to reveal probable OT strains. Rodents were assessed for OT exposure by immunofluorescent antibody assay. Lastly, incidence rate of scrub typhus in each county was associated with loads and prevalence of chigger infestations, seropositivity rate in rodents, and OT positivity rate in chiggers. RESULTS: Rattus losea was the most abundant (48.7% of 1,285 individuals) and widespread (occurred in nine counties) small mammal species and hosted the majority of chiggers (76.4% of 128,520 chiggers). Leptotrombidium deliense was the most common (64.9% of all identified chiggers) and widespread (occurred in seven counties) chigger species but was replaced by Leptotrombidium pallidum or Leptotrombidium scutellare during the cold seasons in two counties (Matsu and Kinmen) where winter temperatures were lower than other study sites. Seropositivity rate for OT exposure in 876 assayed rodents was 43.0% and OT positivity rate in 347 pools of chiggers was 55.9%, with 15 OT strains identified in the 107 successfully sequenced samples. Incidence rate of scrub typhus was positively correlated with chigger loads, prevalence of chigger infestations, seropositivity rate but not OT positivity rate in chiggers. CONCLUSIONS: Our study reveals R. losea as the primary host for chiggers and there exists a geographical and seasonal variation in chigger species in Taiwan. It also emphasizes the importance of recognition of chigger vectors and their vertebrate hosts for a better prediction of human risks to scrub typhus under rapid environmental changes. SN - 1756-3305 UR - https://www.unboundmedicine.com/medline/citation/26626287/Surveillance_of_potential_hosts_and_vectors_of_scrub_typhus_in_Taiwan_ L2 - https://parasitesandvectors.biomedcentral.com/articles/10.1186/s13071-015-1221-7 DB - PRIME DP - Unbound Medicine ER -