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Sarcoptes scabiei

By Therese Ihrig

Geographic Range

Scabies mites have a worldwide distribution. Humans are their primary definitive host. These mites are typically found more frequently in impoverished countries, likely due to lack of sanitation, treatment, and other resources. ("Sarcoptes scabiei:parasites and health", 2009; Heukelbach and Hermann, 2006)

Habitat

Scabies mites are human skin parasites, burrowing into the upper skin layer, never below the stratum corneum (the outermost layer of skin, consisting of only dead cells). Scabies mites penetrate and burrow into the skin more easily where the skin is thin and are found in highest concentrations there, with 63% of mites found on the hands and wrists, 11% on elbows, 9% on feet and ankles, 12% in genital areas, and 2% in armpits. These mites are not typically found in desert areas. They are most commonly transmitted through skin-to-skin contact and, if not on a host, can only survive for a few days. ("Sarcoptes scabiei:parasites and health", 2009; Heukelbach and Hermann, 2006; Ogg, 2011; Roecken, et al., 2003)

Physical Description

Females are 0.30-0.45 mm long and 0.25-0.35 mm wide; males tend to be two-thirds to half that size. The body is oval-shaped, ventrally flattened, and dorsally convex, with the dorsal surfaces covered in setae. There are four pairs of legs, with the two most anterior pairs having cushion-like sucker pads (pulvilli) that are used to hold onto the host's skin. They have an anterior feeding structure called a capitulum and a posterior anus. These mites are blind. ("Sarcoptes scabiei:parasites and health", 2009; Arlian, 1989)

  • Sexual Dimorphism
  • female larger
  • Range length
    0.30 to 0.45 mm
    0.01 to 0.02 in

Development

Females deposit 2-3 eggs per day for their entire lives (1-2 months). Eggs are oval and 0.10 to 0.15 mm in length. Eggs hatch into larvae with three pairs of legs within 3-4 days. They go to the surface of the host's skin and tunnel back in, creating short burrows called molting pouches. After another 3-4 days, larvae molt into nymphs with four pairs of legs, and continue to molt until reaching adulthood (determined mainly by size). Nymphs and larvae may be found in molting pouches or hair follicles. Under ideal conditions, 10% of eggs reach adulthood. ("Sarcoptes scabiei:parasites and health", 2009; Bush, et al., 2001; Ogg, 2011)

Reproduction

Males burrow into female molting pouches, where mating occurs. Once a male has mated with a female, she will remain fertile and capable of laying eggs for the rest of her life. ("Sarcoptes scabiei:parasites and health", 2009; Ogg, 2011)

Females lay eggs throughout their lifetime (1-2 months), all along their burrows in their host's skin. They typically lay 2-3 eggs per day. Eggs hatch within 3-4 days. Hosts do not generally feel the effects of infestation for 6 weeks, at which time their bodies react, typically with intense itching, to excretions and secretions from the mites. ("Sarcoptes scabiei:parasites and health", 2009; Ogg, 2011)

  • Breeding interval
    A female scabies mite will mate once in her lifetime.
  • Breeding season
    Scabies mites will lay eggs throughout their lifetimes.
  • Range number of offspring
    60 to 90
  • Range gestation period
    3 to 4 days

This species exhibits no parental investment. ("Sarcoptes scabiei:parasites and health", 2009)

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

Scabies mites that are not attached to a host will die within 2-3 days at 25°C and within 10 minutes at 49°C. Survival when not attached to a host varies depending on temperature and humidity. Expected lifespan of mites on a host is 1-2 months. ("Sarcoptes scabiei:parasites and health", 2009; Heukelbach and Hermann, 2006; Ogg, 2011)

  • Typical lifespan
    Status: wild
    1 to 2 months

Behavior

Although multiple mites will infect a host, they do not exhibit any social or colonial behavior. Males only create burrows to find a mate, and are generally found wandering and feeding on the host's skin. Once they have mated, females use their mouthparts to lengthen their molting burrows in a characteristically serpentine manner, laying eggs all along it. ("Sarcoptes scabiei- scabies", 2011; Arlian, et al., 1984; Heukelbach and Hermann, 2006)

Home Range

The home range of these mites is generally confined to one host; transmission between hosts is possible mainly via skin-to-skin contact. ("Sarcoptes scabiei:parasites and health", 2009)

Communication and Perception

Some variants of scabies mites are capable of detecting odor and thermal stimuli, enabling them to find a host again quickly should they be removed. They may also be attracted to lipid compounds found on host's skin. (Arlian and Vyszenski-moher, 1995; Arlian, 1989)

Food Habits

Scabies mites ingest cell liquids and skin cells from their hosts. ("Sarcoptes scabiei- scabies", 2011; Ogg, 2011)

  • Animal Foods
  • mammals

Predation

There are no known predators of these human skin parasites.

Ecosystem Roles

There are many variants of scabies mites which infect different types of hosts. For example, Sarcoptes scabiei var. canus, infects dogs and Sarcoptes scabiei var. Suis infects pigs. In humans, their secretions and excretions, in particular, cause allergic reactions and intense itching, often with a blister-like rash. Secondary bacterial skin infections may be caused from scratching areas of infestation, particularly to individuals with compromised immune systems. ("Arthropods", 2011; "Sarcoptes scabiei:parasites and health", 2009; Arlian, 1989; Ogg, 2011)

Species Used as Host

Economic Importance for Humans: Positive

Research is ongoing to find effective treatments and prevention of scabies mite infections. (Arlian, 1989; Heukelbach and Hermann, 2006; Ogg, 2011)

  • Positive Impacts
  • research and education

Economic Importance for Humans: Negative

This skin parasite is harmful to humans, causing severe dermal allergic reactions. Individuals with compromised immune systems may develop what is known as "Norwegian scabies," in which thick crusts form over the infected skin. Different variations of scabies affect many other animals, including livestock. ("Sarcoptes scabiei:parasites and health", 2009; Heukelbach and Hermann, 2006)

Conservation Status

The worldwide population size of this species is very large and dispersed. It has not been considered for conservation status by any agency. (IUCN, 2012)

Other Comments

Correlations have been shown between high volumes of people living together in tight spaces and increased infection rates; some studies show a higher rate of scabies infection in the winter months. Both of these conditions are likely due to increased contact between hosts. ("Sarcoptes scabiei:parasites and health", 2009; Heukelbach and Hermann, 2006)

Contributors

Therese Ihrig (author), Radford University, Jeremy Wright (editor), University of Michigan-Ann Arbor.

Glossary

Antarctica

lives on Antarctica, the southernmost continent which sits astride the southern pole.

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

causes disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

cosmopolitan

having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

crepuscular

active at dawn and dusk

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

infrared/heat

(as keyword in perception channel section) This animal has a special ability to detect heat from other organisms in its environment.

internal fertilization

fertilization takes place within the female's body

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

parasite

an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

polar

the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

polygynous

having more than one female as a mate at one time

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scrub forest

scrub forests develop in areas that experience dry seasons.

semelparous

offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

taiga

Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

tundra

A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

year-round breeding

breeding takes place throughout the year

References

2011. "Arthropods" (On-line). Science clarified. Accessed November 26, 2011 at http://www.scienceclarified.com/Al-As/Arthropods.html#ixzz1fiaRjRO0.

2011. "Sarcoptes scabiei- scabies" (On-line). Parasites in humans. Accessed October 25, 2011 at http://www.parasitesinhumans.org/sarcoptes-scabiei-scabies.html.

2009. "Sarcoptes scabiei:parasites and health" (On-line). Accessed November 03, 2011 at http://dpd.cdc.gov/dpdx/html/Scabies.htm.

Arlian, L., R. Runyan, L. Sorlie, S. Estes. 1984. Host-seeking behavior of Sarcoptes scabiei. Journal of the American Academy of Dermatology, 11/4: 594-598. Accessed November 03, 2011 at http://www.sciencedirect.com/science/article/pii/S019096228470212X.

Arlian, L., D. Vyszenski-moher. 1995. Response of sarcoptes scabiei var. canis (acari: sarcoptidae) to lipids of mammalian. Journal of Medical Entomology, 32/1: 34-41(8). Accessed November 30, 2011 at http://www.ingentaconnect.com/content/esa/jme/1995/00000032/00000001/art00008.

Arlian, L. 1989. Biology, host relations, and epidemiology of Sarcptes scabiei. Annual Review of Entymology, 34: 139-161. Accessed February 28, 2013 at http://129.123.92.202/biol3500/Secure/Other%20Readings/Reviews/scabies%20review.pdf.

Bush, A., J. Fernandez, G. Esch, J. Seed. 2001. Parasitism: the diversity and ecology of animal parasites. New York: Cambridge University Press.

Heukelbach, J., F. Hermann. 2006. Scabies. The Lancet, 367/9524: 1767-1774. Accessed November 13, 2011 at http://www.sciencedirect.com/science/article/pii/S0140673606687722.

IUCN, 2012. "The IUCN Red List of Threatened Species" (On-line). Accessed March 02, 2013 at www.iucnredlist.org.

Johnston, G., M. Sladden. 2005. Scabies: diagnosis and treatment. BMJ, 331/7517: 619-622. Accessed November 13, 2011 at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1215558/.

Ogg, B. 2011. "Scabies mite" (On-line). Accessed November 04, 2011 at http://lancaster.unl.edu/pest/resources/MedicalMites.shtml.

Roecken, M., G. Grevers, W. Bergdorf. 2003. Color atlas of allergic diseases. Stuttgart, Germany: Gorge thieme verlag. Accessed November 13, 2011 at http://books.google.com/books?id=ywd89F7Eni4C&pg=PT84&lpg=PT84&dq=are+scabies+found+in+polar+regions&source=bl&ots=RM-L4V-JGv&sig=GGGsJXvhv8CRH7jHuGrYUfrmuK0&hl=en&ei=UordTpfQNMOa0QGWuPGsBw&sa=X&oi=book_result&ct=result&resnum=1&ved=0CBwQ6AEwAA#v=onepage&q=scabies&f=false.

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