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Volume 32, Number 2—February 2026

Research

Leptotrombidium imphalum Chiggers as Vector for Scrub Typhus in Human Settlements, India, 2022–2023

Carol S. Devamani, Neal Alexander, Rawadee Kumlert, Benjamin L. Makepeace, Serge Morand, Mary Cameron, Alexandr A. Stekolnikov, Winsley Rose, Daniel Chandramohan, Punam Mangtani, Kundavaram P.P. Abhilash, and Wolf-Peter SchmidtComments to Author 
Author affiliation: Christian Medical College, Vellore, India (C.S. Devamani, W. Rose, K.P.P. Abhilash); London School of Hygiene and Tropical Medicine, London, UK (N. Alexander, M. Cameron, D. Chandramohan, P. Mangtani, W.-P. Schmidt); Ministry of Public Health, Nonthaburi, Thailand (R. Kumlert); University of Liverpool, Liverpool, UK (B.L. Makepeace); Centre National de la Recherche Scientifique, France–Kasetsart University and Mahidol University, Bangkok, Thailand (S. Morand); Zoological Institute of the Russian Academy of Sciences, St. Petersburg, Russia (A.A. Stekolnikov)

Main Article

Table 2

Chiggers identified by host species in study of Leptotrombidium imphalum chiggers as vector for scrub typhus in human settlements, India, 2022–2023*

Chigger species Black rat, 
n = 277 Greater bandicoot rat, n = 284 Indian gerbil, n = 12 Mouse, n = 22 Three-striped Indian palm squirrel, n = 14 Asian house shrew, n = 273 Asian gray mongoose, n = 1 Total, n = 883
L. imphalum 769 (48.7) 967 (59.9) 80 (75.0) 6 (13.6) 20 (35.7) 2,470 (75.1) 7 (100.0) 4,319 (59.8)
Chigger index (SD)
 11.7 (26.5)
 34.3 (55.8)
 59.9 (91.1)
 0.9 (3.3)
 3.7 (6.8)
 53.9 (74.4)
 14.2 (NA)
 32.3 (58)
Leptotrombidium sp. 2 (0.7) 0 0 0 1 (7.1) 1 (0.4) 0 4 (0.5)
Chigger index (SD)
 0.04 (0.5)
 0
 0
 0
 0.15 (0.5)
 0.01 (0.2)
 0
 0.02 (0.3)
Ericotrombidium bhattipadense 1,098 (63.2) 2,348 (90.1) 4 (16.7) 18 (4.5) 25 (57.1) 665 (51.3) 1 (100.0) 4,159 (66.0)
Chigger index (SD)
 13.8 (24.4)
 83 (85.3)
 0.7 (1.6)
 2.4 (11.3)
 4.7 (6.2)
 12.9 (30.1)
 2.8 (NA)
 35.2 (62.4)
Hypotrombidium sp. 360 (27.1) 134 (18.7) 8 (16.7) 3 (9.1) 122 (78.6) 5 (0.7) 0 632 (16.4)
Chigger index (SD)
 6 (21.8)
 5.2 (17.7)
 1.4 (3.8)
 0.3 (1)
 37.7 (50.5)
 0.1 (0.8)
 0
 4.2 (17.7)
Ericotrombidium or Hypotrombidium sp. 13 (1.4) 8 (1.4) 0 0 0 0 0 21 (0.9)
Chigger index (SD)
 0.2 (2.1)
 0.2 (2.8)
 0
 0
 0
 0
 NA
 0.1 (2)
Trombicula hypodermata 1 (0.4) 3 (1.1) 0 0 0 165 (19.4) 0 169 (6.5)
Chigger index (SD)
 0.02 (0.3)
 0.1 (0.8)
 0
 0
 0
 2.4 (6.6)
 NA
 0.8 (3.9)
Microtrombicula kajutekrii 519 (27.4) 2 (0.4) 0 1 (4.5) 0 0 0 522 (8.8)
Chigger index (SD)
 5.7 (17.2)
 0.01 (0.1)
 0
 0.05 (0.2)
 0
 0
 NA
 1.8 (10)
Schoengastia tuberculata 9 (1.8) 33 (5.3) 0 0 0 0 0 42 (2.3)
Chigger index (SD)
 0.1 (1.4)
 0.9 (4.5)
 0
 0
 0
 0
 NA
 0.3 (2.7)
Schoengastiella ligula 271 (22.7) 1,826 (76.4) 37 (50.0) 2 (4.5) 0 12 (2.6) 0 2,148 (33.3)
Chigger index (SD)
 3.4 (13.7)
 71.9 (112.1)
 7.4 (14.6)
 0.3 (1.5)
 0
 0.1 (1)
 NA
 24.3 (71.9)
S. liota 0 0 2 (16.7) 0 0 6 (1.1) 0 8 (0.6)
Chigger index (SD)
 0
 0
 0.45 (1.1)
 0
 0
 0.03 (0.3)
 NA
 0.02 (0.2)
S. punctata 1 (0.4) 0 0 0 0 18 (4.4) 0 19 (1.5)
Chigger index (SD)
 0.04 (0.6)
 0
 0
 0
 0
 0.3 (1.9)
 NA
 0.1 (1.1)
S. ralagea 7 (1.1) 13 (4.2) 0 0 0 173 (15.4) 0 193 (6.5)
Chigger index (SD)
 0 (0.4)
 0.7 (4)
 0
 0
 0
 6.6 (45.7)
 NA
 2.3 (25.6)
S. argalea 0 0 1 (8.3) 0 0 3 (0.7) 0 4 (0.3)
Chigger index (SD)
 0
 0
 0.2 (0.7)
 0
 0
 0.04 (0.6)
 NA
 0 (0.3)
S. ceylonica 20 (1.1) 1 (0.4) 5 (8.3) 53 (40.9) 0 0 0 79 (1.6)
Chigger index (SD)
 0.1 (1.7)
 0.03 (0.6)
 1.8 (6.3)
 6.2 (17.3)
 0
 0
 NA
 0.2 (3.1)
S. bengalensis 0 1 (0.4) 0 0 0 23 (5.9) 0 24 (1.9)
Chigger index (SD)
 0
 0.01 (0.2)
 0
 0
 0
 0.23 (1.2)
 NA
 0.07 (0.7)
S. singularis 0 0 40 (41.7) 0 0 0 0 40 (0.6)
Chigger index (SD)
 0
 0
 28.8 (51.8)
 0
 0
 0
 NA
 0.4 (6.7)
Walchia sp. 0 0 0 8 (18.2) 0 37 (9.2) 0 45 (3.3)
Chigger index (SD)
 0
 0
 0
 0.8 (2.2)
 0
 0.3 (1.7)
 NA
 0.1 (1)
Gahrliepia khandalaensis 0 1 (0.4) 0 0 0 2 (0.4) 0 3 (0.2)
Chigger index (SD)
 0
 0.01 (0.1)
 0
 0
 0
 0.04 (0.6)
 NA
 0.01 (0.3)
Total 3,070 (92.1) 5,337 (99.3) 177 (100.0) 91 (63.6) 168 (92.9) 3,580 (91.2) 8 (100.0) 12,431 (93.5)
Chigger index (SD) 41.4 (50.2) 196.4 (148.3) 100.7 (106.4) 11 (22.6) 46.2 (49.5) 77 (98.1) 17 (NA) 102.4 (124.4)

*Chigger species and total values are no. chiggers (% infestation). Chigger index is mean number of chiggers per host. NA, not applicable.

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Page created: January 20, 2026
Page updated: February 19, 2026
Page reviewed: February 19, 2026
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