Leptotrombidium
Encyclopedia
Leptotrombidium is a genus of mite
s in the family Trombiculidae
, that are able to infect humans with scrub typhus
(Orientia tsutsugamushi
infection) through their bite. 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. 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). Instead, the bacterium persists in the mites through transovarial transmission
, where infected mites transmit the infection to their unborn offspring. Leptotrombidium mites are therefore both vector and reservoir for O. tsutsugamushi. The infection predominantly affects female mites, and does not appear to otherwise harm the mites.
The larval mites feed on liquified skin tissue, not blood, as their mouth parts (chelicerae) are too short to reach the blood vessels. The larvae most commonly target rodents, but will also attach to humans. 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.
After feeding, the larvae drop to the ground and become nymphs, then mature into adults which have 8 legs and are harmless to humans. In the post larval stage, they are not parasitic and feed on plant materials.
Mite
Mites, along with ticks, are small arthropods belonging to the subclass Acari and the class Arachnida. The scientific discipline devoted to the study of ticks and mites is called acarology.-Diversity and systematics:...
s in the family Trombiculidae
Trombiculidae
Trombiculidae is a family of mites called trombiculid mites Trombiculidae is a family of mites called trombiculid mites Trombiculidae is a family of mites called trombiculid mites (also called berry bugs; harvest mites; red bugs; scrub-itch mites; and aoutas. In their larval stage, those...
, that are able to infect humans with scrub typhus
Scrub typhus
Scrub typhus or Bush typhus is a form of typhus caused by Orientia tsutsugamushi first isolated and identified in 1930 in Japan., accessdate: 16 October 2011...
(Orientia tsutsugamushi
Orientia tsutsugamushi
Orientia tsutsugamushi is the causative organism of scrub typhus, and the natural vector and reservoir is probably trombiculid mites ....
infection) through their bite. 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. 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). Instead, the bacterium persists in the mites through transovarial transmission
Transovarial transmission
Transovarian transmission occurs in certain arthropod vectors as they transmit disease-causing bacteria from parent arthropod to offspring arthropod. For instance, Rickettsia rickettsii, carried within ticks, is passed on from parent to offspring tick by transovarial transmission...
, where infected mites transmit the infection to their unborn offspring. Leptotrombidium mites are therefore both vector and reservoir for O. tsutsugamushi. The infection predominantly affects female mites, and does not appear to otherwise harm the mites.
The larval mites feed on liquified skin tissue, not blood, as their mouth parts (chelicerae) are too short to reach the blood vessels. The larvae most commonly target rodents, but will also attach to humans. 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.
After feeding, the larvae drop to the ground and become nymphs, then mature into adults which have 8 legs and are harmless to humans. In the post larval stage, they are not parasitic and feed on plant materials.
Taxonomy
- L. akamushi is endemic to Japan and is the reservoir for the Kato serotypeSerotypeSerotype or serovar refers to distinct variations within a subspecies of bacteria or viruses. These microorganisms, viruses, or cells are classified together based on their cell surface antigens...
of Orientia tsutsugamushiOrientia tsutsugamushiOrientia tsutsugamushi is the causative organism of scrub typhus, and the natural vector and reservoir is probably trombiculid mites ....
; - L. delienseLeptotrombidium delienseLeptotrombidium deliense is a species of mite.It is a vector of scrub typhus....
is the main vector in the south of China and in Thailand; it is also endemic to Litchfield ParkLitchfield National ParkLitchfield National Park, covering approximately 1500 km2, is near the township of Batchelor, 100 km south-west of Darwin, in the Northern Territory of Australia...
, in the Northern Territory, Australia, where is carries the Litchfield serotype. - L. pallidum is endemic to Japan and is the reservoir for Karp and Gilliam serotypes;
- L. scutellare is endemic to Japan and is the reservoir for Kawasaki and Kuroki serotypes.