An Ecological Survey of Chiggers (Acariformes: Trombiculidae) Associated with Small Mammals in an Epidemic Focus of Scrub Typhus on the China–Myanmar Border in Southwest China
Chiggers (chigger mites) are a group of tiny arthropods, and they are the exclusive vector of <i>Orientia tsutsugamushi</i> (Ot), the causative agent of scrub typhus (tsutsugamushi disease). Dehong Prefecture in Yunnan Province of southwest China is located on the China–Myanmar border an...
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2024-10-01
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| author | Ru-Jin Liu Xian-Guo Guo Cheng-Fu Zhao Ya-Fei Zhao Pei-Ying Peng Dao-Chao Jin |
| author_facet | Ru-Jin Liu Xian-Guo Guo Cheng-Fu Zhao Ya-Fei Zhao Pei-Ying Peng Dao-Chao Jin |
| author_sort | Ru-Jin Liu |
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| description | Chiggers (chigger mites) are a group of tiny arthropods, and they are the exclusive vector of <i>Orientia tsutsugamushi</i> (Ot), the causative agent of scrub typhus (tsutsugamushi disease). Dehong Prefecture in Yunnan Province of southwest China is located on the China–Myanmar border and is an important focus of scrub typhus. Based on the field surveys in Dehong between 2008 and 2022, the present paper reports the infestation and ecological distribution of chiggers on the body surface of rodents and other sympatric small mammals (shrews, tree shrews, etc.) in the region for the first time. The constituent ratio (<i>C<sub>r</sub></i>), prevalence (<i>P<sub>M</sub></i>), mean abundance (<i>MA</i>), and mean intensity (<i>MI</i>) were routinely calculated to reflect the infestation of small-mammal hosts with chiggers. Additionally, the species richness (<i>S</i>), Shannon–Wiener diversity index (<i>H</i>), Simpson dominance index (<i>D</i>), and Pielou’s evenness index (<i>E</i>) were calculated to illustrate the chigger community structure. Preston’s log-normal model was used to fit the theoretical curve of species abundance distribution, and the Chao 1 formula was used to roughly estimate the expected total species. The “corrplot” package in R software (Version 4.3.1) was used to analyze interspecific relationships, and the online drawing software was used to create a chord diagram to visualize the host–chigger associations. From 1760 small-mammal hosts, a total of 9309 chiggers were identified as belonging to 1 family, 16 genera, and 117 species, with high species diversity. The dominant chigger species were <i>Leptotrombidium deliense</i>, <i>Walchia ewingi</i>, and <i>Gahrliepia longipedalis</i>, with a total <i>C<sub>r</sub></i> = 47.65% (4436/9309), among which <i>L. deliense</i> is the most important vector of Ot in China. The overall infestation indexes (<i>P<sub>M</sub></i>, <i>MA</i>, and <i>MI</i>) and community parameters (<i>S</i>, <i>H</i>, and <i>E</i>) of chiggers in the mountainous areas and outdoors were higher than those in the flatland areas and indoors, with an obvious environmental heterogeneity. <i>Leptotrombidium deliense</i> was the dominant species in the flatland and indoors, while <i>G. longipedalis</i> was the prevalent species in the mountainous and outdoor areas. The species abundance distribution of the chigger community conformed to log-normal distribution with the theoretical curve equation: <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mi>S</mi><mo>(</mo><mi>R</mi><mo>)</mo></mrow><mo>′</mo></msup><mo>=</mo><mn>28</mn><msup><mi>e</mi><mrow><msup><mrow><mo>−</mo><mo stretchy="false">[</mo><mn>0.23</mn><mo stretchy="false">(</mo><mi>R</mi><mo>−</mo><mn>0</mn><mo stretchy="false">)</mo><mo stretchy="false">]</mo></mrow><mrow><mn>2</mn></mrow></msup></mrow></msup></mrow></semantics></math></inline-formula>, indicating the existence of many rare species and only a few dominant species in the community. The expected total number of chigger species was roughly estimated to be 147 species, 30 more than the 117 species actually collected, suggesting that some uncommon species may have been missed in the sampling survey. The host–parasite association analysis revealed that one host species can harbor different chigger species, and one chigger species can parasitize different host species with low host specificity. A positive or negative correlation existed among different chigger species, indicating a cooperative or competitive interspecific relationship. The species diversity of chiggers is high in Dehong on the China–Myanmar border, and a large host sample is recommended to find more uncommon species. There is an obvious environmental heterogeneity of the chigger community, with different species diversity and dominant species in different environments. The low host specificity of chiggers and the occurrence of a large number of <i>L. deliense</i> in Dehong, especially in flatland areas and indoors, would increase the risk of persistent transmission of scrub typhus in the region. |
| format | Article |
| id | doaj-art-a93f4e95ef334119a99ceb6089b08a48 |
| institution | OA Journals |
| issn | 2075-4450 |
| language | English |
| publishDate | 2024-10-01 |
| publisher | MDPI AG |
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| series | Insects |
| spelling | doaj-art-a93f4e95ef334119a99ceb6089b08a482025-08-20T02:11:05ZengMDPI AGInsects2075-44502024-10-01151081210.3390/insects15100812An Ecological Survey of Chiggers (Acariformes: Trombiculidae) Associated with Small Mammals in an Epidemic Focus of Scrub Typhus on the China–Myanmar Border in Southwest ChinaRu-Jin Liu0Xian-Guo Guo1Cheng-Fu Zhao2Ya-Fei Zhao3Pei-Ying Peng4Dao-Chao Jin5Institute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali 671000, ChinaInstitute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali 671000, ChinaInstitute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali 671000, ChinaInstitute of Pathogens and Vectors, Yunnan Provincial Key Laboratory for Zoonosis Control and Prevention, Dali University, Dali 671000, ChinaInstitute of Microbiology, Qujing Medical College, Qujing 655100, ChinaInstitute of Entomology, Guizhou University, Guiyang 550025, ChinaChiggers (chigger mites) are a group of tiny arthropods, and they are the exclusive vector of <i>Orientia tsutsugamushi</i> (Ot), the causative agent of scrub typhus (tsutsugamushi disease). Dehong Prefecture in Yunnan Province of southwest China is located on the China–Myanmar border and is an important focus of scrub typhus. Based on the field surveys in Dehong between 2008 and 2022, the present paper reports the infestation and ecological distribution of chiggers on the body surface of rodents and other sympatric small mammals (shrews, tree shrews, etc.) in the region for the first time. The constituent ratio (<i>C<sub>r</sub></i>), prevalence (<i>P<sub>M</sub></i>), mean abundance (<i>MA</i>), and mean intensity (<i>MI</i>) were routinely calculated to reflect the infestation of small-mammal hosts with chiggers. Additionally, the species richness (<i>S</i>), Shannon–Wiener diversity index (<i>H</i>), Simpson dominance index (<i>D</i>), and Pielou’s evenness index (<i>E</i>) were calculated to illustrate the chigger community structure. Preston’s log-normal model was used to fit the theoretical curve of species abundance distribution, and the Chao 1 formula was used to roughly estimate the expected total species. The “corrplot” package in R software (Version 4.3.1) was used to analyze interspecific relationships, and the online drawing software was used to create a chord diagram to visualize the host–chigger associations. From 1760 small-mammal hosts, a total of 9309 chiggers were identified as belonging to 1 family, 16 genera, and 117 species, with high species diversity. The dominant chigger species were <i>Leptotrombidium deliense</i>, <i>Walchia ewingi</i>, and <i>Gahrliepia longipedalis</i>, with a total <i>C<sub>r</sub></i> = 47.65% (4436/9309), among which <i>L. deliense</i> is the most important vector of Ot in China. The overall infestation indexes (<i>P<sub>M</sub></i>, <i>MA</i>, and <i>MI</i>) and community parameters (<i>S</i>, <i>H</i>, and <i>E</i>) of chiggers in the mountainous areas and outdoors were higher than those in the flatland areas and indoors, with an obvious environmental heterogeneity. <i>Leptotrombidium deliense</i> was the dominant species in the flatland and indoors, while <i>G. longipedalis</i> was the prevalent species in the mountainous and outdoor areas. The species abundance distribution of the chigger community conformed to log-normal distribution with the theoretical curve equation: <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mi>S</mi><mo>(</mo><mi>R</mi><mo>)</mo></mrow><mo>′</mo></msup><mo>=</mo><mn>28</mn><msup><mi>e</mi><mrow><msup><mrow><mo>−</mo><mo stretchy="false">[</mo><mn>0.23</mn><mo stretchy="false">(</mo><mi>R</mi><mo>−</mo><mn>0</mn><mo stretchy="false">)</mo><mo stretchy="false">]</mo></mrow><mrow><mn>2</mn></mrow></msup></mrow></msup></mrow></semantics></math></inline-formula>, indicating the existence of many rare species and only a few dominant species in the community. The expected total number of chigger species was roughly estimated to be 147 species, 30 more than the 117 species actually collected, suggesting that some uncommon species may have been missed in the sampling survey. The host–parasite association analysis revealed that one host species can harbor different chigger species, and one chigger species can parasitize different host species with low host specificity. A positive or negative correlation existed among different chigger species, indicating a cooperative or competitive interspecific relationship. The species diversity of chiggers is high in Dehong on the China–Myanmar border, and a large host sample is recommended to find more uncommon species. There is an obvious environmental heterogeneity of the chigger community, with different species diversity and dominant species in different environments. The low host specificity of chiggers and the occurrence of a large number of <i>L. deliense</i> in Dehong, especially in flatland areas and indoors, would increase the risk of persistent transmission of scrub typhus in the region.https://www.mdpi.com/2075-4450/15/10/812chigger mitevectorectoparasitesmall mammalecologyChina–Myanmar border |
| spellingShingle | Ru-Jin Liu Xian-Guo Guo Cheng-Fu Zhao Ya-Fei Zhao Pei-Ying Peng Dao-Chao Jin An Ecological Survey of Chiggers (Acariformes: Trombiculidae) Associated with Small Mammals in an Epidemic Focus of Scrub Typhus on the China–Myanmar Border in Southwest China Insects chigger mite vector ectoparasite small mammal ecology China–Myanmar border |
| title | An Ecological Survey of Chiggers (Acariformes: Trombiculidae) Associated with Small Mammals in an Epidemic Focus of Scrub Typhus on the China–Myanmar Border in Southwest China |
| title_full | An Ecological Survey of Chiggers (Acariformes: Trombiculidae) Associated with Small Mammals in an Epidemic Focus of Scrub Typhus on the China–Myanmar Border in Southwest China |
| title_fullStr | An Ecological Survey of Chiggers (Acariformes: Trombiculidae) Associated with Small Mammals in an Epidemic Focus of Scrub Typhus on the China–Myanmar Border in Southwest China |
| title_full_unstemmed | An Ecological Survey of Chiggers (Acariformes: Trombiculidae) Associated with Small Mammals in an Epidemic Focus of Scrub Typhus on the China–Myanmar Border in Southwest China |
| title_short | An Ecological Survey of Chiggers (Acariformes: Trombiculidae) Associated with Small Mammals in an Epidemic Focus of Scrub Typhus on the China–Myanmar Border in Southwest China |
| title_sort | ecological survey of chiggers acariformes trombiculidae associated with small mammals in an epidemic focus of scrub typhus on the china myanmar border in southwest china |
| topic | chigger mite vector ectoparasite small mammal ecology China–Myanmar border |
| url | https://www.mdpi.com/2075-4450/15/10/812 |
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