関: chigger、red bug、trombiculid mite、Trombiculidae

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mites (同)family Trombiculidae

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ツツガムシ(ダニの一種) / スナノミ(南米・アフリカ産のノミ)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/07/20 11:38:03」(JST)

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Leptotrombidium /ˌlɛptɵtrɒmˈbɪdiːəm/ is a genus of mites in the family Trombiculidae, that are able to infect humans with scrub typhus (Orientia tsutsugamushi infection) through their bite.^[1] The larval form (called chiggers) feeds on rodents, but also occasionally humans and other large mammals. They are related to the harvest mites of the North America and Europe.

It was originally thought that rodents were the main reservoir for O. tsutsugamushi and that the mites were merely vectors of infection: that is, the mites only transferred the contagion from the rodents to humans.^[2]^[3] However, it is now known that the mites only feed once in their lifetime, which means that transmission from rodent to human via the mites is impossible (for it to have been possible, the mite would have to feed at least twice, once on the infected rodent and again on the human who would then be infected).^[4] Instead, the bacterium persists in the mites through transovarial transmission,^[5]^[6]^[7] where infected mites transmit the infection to their unborn offspring. Leptotrombidium mites are therefore both vector and reservoir for O. tsutsugamushi.^[4] The infection predominantly affects female mites,^[8] and does not appear to otherwise harm the mites.

Life history[edit]

The larva is pale orange in colour and feeds on liquified skin tissue, not blood, as their mouth parts (chelicerae) are too short to reach the blood vessels.^[9] They have 3 pairs of legs. The larvae most commonly target rodents, but will also attach to humans.^[4] For humans, the bite is painless, but pain commonly develops only after the larva detaches from the skin, leaving a red papule that may then develop into an eschar.^[10]

The larval stage lasts for 1 to 2 weeks. After feeding, the larvae drop to the ground and become nymphs. Nymph is brick-red in colour and has 4 pairs of legs. Nymphal stage lasts for 1 to 3 weeks. Nymphs mature into adults which have 4 pairs of legs, first pair being the largest. They are harmless to humans. In the post larval stage, they are not parasitic and feed on plant materials.^[11] Female lays eggs singly, which hatch in about a week. Lifespan of adult is about 6 months.

Taxonomy[edit]

L. akamushi is endemic to Japan and is the reservoir for the Kato serotype of Orientia tsutsugamushi;^[1]
L. deliense is the main vector in the south of China^[12] and in Thailand;^[13] it is also endemic to Litchfield Park, in the Northern Territory, Australia, where is carries the Litchfield serotype.^[14]
L. pallidum is endemic to Japan and is the reservoir for Karp and Gilliam serotypes;^[1]^[15]
L. scutellare is endemic to Japan and is the reservoir for Kawasaki and Kuroki serotypes.^[1]^[15]

References[edit]

^ ^a ^b ^c ^d "Scrub typhus (tsutsugamushi disease) in Japan, 1996–2000". Byogen Biseibutsu Kenshutsu Joho Geppo 22: 211–212. 2001.
^ Philip CB (1948). "Tsutsugamushi disease (scrub typhus) in World War II". J Parasitol 34 (3): 169–191. doi:10.2307/3273264. JSTOR 3273264.
^ Fox JP (1948). "The long persistence of Rickettsia orientalis in the blood and tissues of infected animals". J Immunol 59 (2): 109–114.
^ ^a ^b ^c Pham XD, Suzuki H, Takaoka H (2001). "Distribution of unengorged larvae of Leptotrombidium pallidum and other species in and around the rodent nest holes". Southeast Asian J Trop Med Public Health 32 (3): 553–57. PMID 11944716.
^ Walker JS, Chan CT, Manikumaran C, Elisberg BL (1975). "Attempts to infect and demonstrate transovarial transmission of R. tsutsugamushi in three species of Leptotrombidium mites". Ann NY Acad Sci 266: 80–90. doi:10.1111/j.1749-6632.1975.tb35090.x.
^ Takahashi M, Murata M, Nogami S, Hori E, Kawamura A, Tanaka H (1988). "Transovarial transmission of Rickettsia tsutsugamushi in Leptotrombidium pallidum successively reared in the laboratory". Jpn J Exp Med 58: 213–218.
^ Frances SP, Watcharapichat P, Phulsuksombati D (2001). "Vertical transmission of Orientia tsutsugamushi in two lines of naturally infected Leptotrombidium deliense (Acari: Trombiculidae)". J Med Entomol 38 (1): 17–21. doi:10.1603/0022-2585-38.1.17. PMID 11268685.
^ Roberts LW, Rapmund G, Gadigan FG (1977). "Sex ratios in Rickettsia tsutsugamushi-infected and noninfected colonies of Leptotrombidium (Acari: Trombiculidae)". J Med Entomol 14 (1): 89–92.
^ Roberts LW, Robinson DM, Rapmund G, et al. (1975). "Distribution of Rickettsia tsutsugamushi in organs of Leptotrombidium (Leptotrombidium) fletcheri (Prostigmata: Trombiculidae)". J Med Entomol 12 (3): 345–348.
^ Kitaoka M, Asanuma K, Otsuji J (1974). "Transmission of Rickettsia orientalis to man by Leptotrombidium akamushi at a scrub typhus endemic area in Akita Prefecture, Japan". Am J Trop Med Hyg 23 (5): 993–9. PMID 4451238.
^ Takahashi M, Misumi H, Urakami H, et al. (2003). "Life cycle of Leptotrombidium pallidum (Acari: Trombiculidae), one of the vector mites of scrub typhus in Japan". Ohara Sogo Byoin Nenpo 45: 19–30.
^ Wang S, Jiang P, Huang J, et al. (2001). "Demonstration of the natural foci of tsutsugamushi disease in Nan Peng Lie Islands in China". The Southeast Asian journal of tropical medicine and public health 32 (3): 541–46. PMID 11944714.
^ Frances SP, Watcharapichat P, Phulsuksombati D, Tanskul P, Linthicum KJ (1999). "Seasonal occurrence of Leptotrombidium deliense (Acari: Trombiculidae) attached to sentinel rodents in an orchard near Bangkok, Thailand". J Med Entomol 36 (6): 869–874. PMID 10593093.
^ Odorico DM, Graves SR, Currie B, et al. (1998). "New Orientia tsutsugamushi strain from scrub typhus in Australia". Emerg Infect Dis 4 (4): 641–4. doi:10.3201/eid0404.980416. PMC 2640248. PMID 9866742.
^ ^a ^b Kawamori F, Akiyama M, Sugieda M, et al. (1992). "Epidemiology of Tsutsugamushi disease in relation to the serotypes of Rickettsia tsutsugamushi isolated from patients, field mice, and unfed chiggers on the eastern slope of Mount Fuji, Shizuoka Prefecture, Japan". J Clin Microbiol 30 (11): 2842–2846. PMC 270539. PMID 1452653.

UpToDate Contents

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1. ツツガ虫病：臨床的特徴および診断 scrub typhus clinical features and diagnosis

English Journal

Characterization Based on the 56-Kda Type-Specific Antigen Gene of Orientia tsutsugamushi Genotypes Isolated from Leptotrombidium Mites and the Rodent Host Post-Infection.

Takhampunya R, Tippayachai B, Promsathaporn S, Leepitakrat S, Monkanna T, Schuster AL, Melendrez MC, Paris DH, Richards AL, Richardson JH.Author information Department of Entomology, United States Army Medical Component - Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand; Viral Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland; Mahidol Oxford Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand; Viral and Rickettsial Diseases Department, Naval Medical Research Center, Silver Spring, Maryland; Entomology Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland.AbstractAbstract. Characterization of the 56-kDa type-specific antigen (TSA) genes of Orientia tsutsugamushi (OT) from three naturally infected, laboratory-reared mite colonies comprising three species (Leptotrombidium deliense [Ld], Leptotrombidium imphalum [Li], and Leptotrombidium chiangraiensis [Lc]) has revealed the presence of single and coexisting OT genotypes found in individual chiggers. The Karp genotype was found in all of the chiggers examined, whereas Gilliam and UT302 genotypes were only observed in combination with the Karp genotype. From analysis of these OT genotypes after transmission from chiggers to mice it was determined that with the Lc and Li mites, the OT genotype composition in the rodent spleens post-infection had not changed and therefore resembled that observed in the feeding chiggers. However, only the Karp genotype was found in rodents after feeding by Ld chiggers carrying Karp and Gilliam genotypes. The current findings reveal a complex association among the host, pathogen, and vector.
The American journal of tropical medicine and hygiene.Am J Trop Med Hyg.2014 Jan;90(1):139-46. doi: 10.4269/ajtmh.13-0393. Epub 2013 Dec 2.
Abstract. Characterization of the 56-kDa type-specific antigen (TSA) genes of Orientia tsutsugamushi (OT) from three naturally infected, laboratory-reared mite colonies comprising three species (Leptotrombidium deliense [Ld], Leptotrombidium imphalum [Li], and Leptotrombidium chiangraiensis [Lc]) ha
PMID 24297814

A new genus and two new species of chigger mites (Acari: Trombiculidae) from the Laotian rock-rat Laonastes aenigmamus Jenkins, Kilpatrick, Robinson & Timmins (Rodentia: Diatomyidae).

Stekolnikov AA.Author information Zoological Institute, Universitetskaya Embankment 1, St. Petersburg, 199034, Russia, trombicula@mail.ru.AbstractA new chigger mite genus Laotrombicula n. g. and two new species, Laotrombicula khunboromi n. sp. (type-species) and L. fangumi n. sp., are described from the Laotian rock-rat Laonastes aenigmamus Jenkins, Kilpatrick, Robinson & Timmins (Rodentia: Diatomyidae). The new genus is most similar to Trombiculindus Radford, 1948 and Leptotrombidium Nagayo, Miyagawa, Mitamura & Imamura, 1916 and differs from these genera by having the scutum of subhexagonal or semicircular shape vs widely rectangular; pinnatifid dorsocentral idiosomal setae vs foliaceous in Trombiculindus and unexpanded in Leptotrombidium; and by the presence of serrated longitudinal crests in the middle part of scutum.
Systematic parasitology.Syst Parasitol.2014 Jan;87(1):21-31. doi: 10.1007/s11230-013-9453-4. Epub 2014 Jan 7.
A new chigger mite genus Laotrombicula n. g. and two new species, Laotrombicula khunboromi n. sp. (type-species) and L. fangumi n. sp., are described from the Laotian rock-rat Laonastes aenigmamus Jenkins, Kilpatrick, Robinson & Timmins (Rodentia: Diatomyidae). The new genus is most similar to T
PMID 24395573

ECTOPARASITE BURDENS OF THE COMMON MOLE-RAT (CRYPTOMYS HOTTENTOTUS HOTTENTOTUS) FROM THE CAPE PROVINCES OF SOUTH AFRICA.

Archer EK, Bennett NC, Ueckermann EA, Lutermann H.Author information University of Pretoria, Mammal Research Institure, Department of Zoology & Entomology, University of Pretoria.AbstractAbstract The members of the African mole-rat family (Bathyergidae) are widely distributed across sub-Saharan Africa. Despite their well-studied biology and reproductive physiology the current knowledge of their ectoparasite fauna is limited and ambiguous due to recent revisions of the bathyergid taxonomy. The common mole-rat (Cryptomys hottentotus hottentotus) is 1 of the most widely distributed species of these subterranean rodents. Ectoparasites were collected from 268 common mole-rats at 2 localities (Western and Northern Cape Province) in South Africa over the course of 18 mo with the aim to document species richness, prevalence and abundance of these ectoparasites. The aggregation of parasite species, sex bias within a species and seasonal variation in ectoparasite burdens were investigated. A total of 4830 individual parasites from 4 mite species (Androlaelaps scapularis, A. capensis, Radfordia ensifera and 1 undetermined chigger (Family Trombiculidae), 1 flea species (Cryptopsylla ingrami) and 1 louse species (Eulinognathus hilli) were collected. With the exception of R. ensifera and the chigger all of these ectoparasites appear to be host specific either for the host species or the Bathyergidae. Aggregation indices indicated that with the exception of E. hilli the distribution of all parasite species was highly aggregated among hosts and sex biased. Seasonal variation in prevalence, abundance and species richness was apparent with greater burdens in the rainy winter season. This is likely related to seasonal variation in abiotic factors but may also be affected by the timing of host reproduction and dispersal behavior.
The Journal of parasitology.J Parasitol.2013 Oct 30. [Epub ahead of print]
Abstract The members of the African mole-rat family (Bathyergidae) are widely distributed across sub-Saharan Africa. Despite their well-studied biology and reproductive physiology the current knowledge of their ectoparasite fauna is limited and ambiguous due to recent revisions of the bathyergid tax
PMID 24171714

Japanese Journal

11月熱福島県中南部におけるタテツツガムシ媒介性つつが虫病

成田雅,鵜沼菜穂子,伊藤文人 [他],佐藤憲行,星野智祥,井上実,山本正悟,安藤秀二,藤田博己
日本内科学会雑誌 101(1), 164-167, 2012-01-10
NAID 10030391425

11月熱　福島県中南部におけるタテツツガムシ媒介性つつが虫病

成田雅,鵜沼菜穂子,伊藤文人,佐藤憲行,星野智祥,井上実,山本正悟,安藤秀二,藤田博己
日本内科学会雑誌 101(1), 164-167, 2012
タテツツガムシによるつつが虫病の臨床像は多彩で見逃されることが多い．病歴（好発時期と好発地域，野外活動歴），バイタルサインと身体所見（発熱，比較的徐脈，発疹，刺し口）から積極的に疑い，疑わしければ直ちにテトラサイクリン系抗菌薬にて治療を開始すべきである．血清学的にはKawasaki型あるいはKuroki型のOrietia tsutsugamushi抗原に対する抗体価の上昇が特異的であるが，これらは …
NAID 130003371628

房総半島南部におけるツツガムシ病の血清学的疫学調査

田中研三,葛西猛,伊藤憲佐,大橋正樹,中井智子,伊藤太一
日本救急医学会雑誌 22(11), 845-851, 2011-11-15
NAID 10030254993

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★リンクテーブル★

リンク元	「アカツツガムシ属」「Trombiculidae」「trombiculid mite」「red bug」「chigger」
拡張検索	「Leptotrombidium属」

「アカツツガムシ属」

Leptotrombidium
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Arachnida
Subclass:	Acari
Order:	Trombidiformes
Family:	Trombiculidae
Subfamily:	Trombiculinae
Genus:	Leptotrombidium; Nagayo et al., 1916