Detection of Orientia tsutsugamushi in Novel Trombiculid Mite Species in Northern Tamil Nadu, India: Use of Targeting the Multicopy traD Gene

Abstract

Detection of Orientia tsutsugamushi DNA in a trombiculid mite chigger species suggests that it might be a potential vector of scrub typhus in an endemic area. Over a period of 20 mo, 85 rats were trapped, 57 had chiggers that were identified by standard morphometric techniques. The chigger pools were assessed by performing PCR assays targeting fragments of the single-copy genes 56 kDa type-specific antigen gene (TSA56) by nested PCR and the 47 kDa (htrA) quantitative real-time PCR (qPCR). The novel traD SYBR green assay that detects a multicopy gene was also performed. In total, 27 chigger pools were positive by traD qPCR, of which only 7 were positive by 47 kDa qPCR and in 3 of these, 56 kDa gene was amplified by nested PCR. Orientia tsutsugamushi-specific DNA was detected in Ascoschoengastia spp., Schoengastiella ligula, Leptotrombidium rajasthanense, Leptotrombidium deliense, and Leptotrombidium jayawickremei chigger pools. Therefore, they could be potential vectors of scrub typhus in Southern India. The three 56 kDa sequences belonged to TA716 genotype and Kato genogroup. Further studies are needed to confirm these chigger species as scrub typhus vectors in Northern Tamil Nadu.

Not Only Leptotrombidium spp. an Annotated Checklist of Chigger Mites (Actinotrichida: Trombiculidae) Associated with Bacterial Pathogens

“…), the Savile’s bandicoot rat Bandicota savilei Thomas, 1916, the greater bandicoot rat B. indica (Bechstein, 1800) (Mammalia: Rodentia), the northern treeshrew Tupaia belangeri (Wagner, 1841) and the common treeshrew T. glis Diard and Duvaucel, 1820 (Mammalia: Scadentia). Reports come from India, Thailand and Vietnam [ 23 , 30 , 46 , 47 , 48 , 49 , 50 ].…”

“…Orientia tsutsugamushi -positive larvae of this species (originally mentioned as Leptotrombidium jayawickremei ) were captured in India while feeding on R. rattus [ 49 ].…”

“…Infected chiggers parasitized small mammals: R. rattus , R. rattus -complex, R. argentiventer , R. tanezumi , the Polynesian rat R. exulans (Peale, 1848), M. cervicolor , B. indica , B. saliviei , the Royle’s mountain vole Alticola roylei (Gray, 1842) (Mammalia: Rodentia) and T. belangeri as well as swarmed on the ground and plants (unfed parasites). Above observations come from India, Indonesia, Pakistan, Taiwan and Thailand [ 29 , 30 , 47 , 49 , 50 , 55 , 68 , 78 , 79 ].…”

“…Bacteria-positive larvae were obtained from A. agrarius , the Indian mole-rat B. bengalensis Gray, 1835, B. indica , A. roylei , R. rattus , the buff-breasted rat R. tanezumi flavipectus (Milne-Edwards, 1872), R. tanezumi , the Sikkim rat R. andamanensis (Blyth, 1860), R. exulans , R. norvegicus , R. losea , Rattus spp., the small white-toothed rat B. berdmorei (Blyth, 1851), T. belangeri (mentioned as T. belangeri persurae ), T. glis and S. murinus (mentioned as S. murinus fulvo-cinerea) as well as from the moist marshlands (host-questing larvae). The above observations were made in Australia, China, India, Indonesia, Malaysia, Myanmar, Pakistan, Papua New Guinea, Philippines, Singapore, Taiwan (including Pescadores), Thailand and Vietnam [ 10 , 14 , 23 , 40 , 46 , 49 , 51 , 52 , 68 , 78 , 83 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 ].…”

“…Genus representatives parasitizing R. rattus were evidenced for the presence of O. tsutsugamushi. Observation from India [ 49 ].…”