Sarcoptes scabiei
Jeffery Cote
Biology 4800
March 18, 2011
Cause of Scabies and Mange
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First identified by Aristotle
1868, formal discovery of
scabies causative agent
Ectoparasite
Class Arachnia
Family Scaroptidae
Sarcoptes scabiei var (variety)
hominis.
Mite, feeds on skin and
blood
Mite life cycle
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Eggs Hatch
1st instar, nymphs dig into
stratum corneum with
mandibles, moult after 3-4
days
2nd instar, protonymphs,
moult after 2-5 days
3rd instar, tritonymphs, moult
after 5-6 days
Adult males and females
Females moult once more
Life cycle continued
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Females, twice as big as males
Female: 0.5mm long
Male: 0.25mm long
Larvae have 6 legs, other stages
have 8.
No respiratory tract
Mating occurs after female’s
second adult moult.
Female produces approx. 40 eggs
after fertilization
Male dies after fertilization*
Fewer than 1% of eggs develop
into adult mites.
Females live in burrow for 30-60
days
Transmission
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Transmission via close sustained contact with infected
individuals, takes at least 30 min to become infected.
Most common route in adults is sex, thusly lumped in
with STDs.
Secondary transfer can occur via contact with the
clothes or towel of an infected person, not likely unless
individual has crusted scabies.
Largely caused by crowding and poor healthcare, no
link to hygiene.
Outbreaks occur in prisons, nursing homes, hospitals.
Symptoms
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Itching, Rash
Pimple like rash (immune
reaction to female’s feeding,
tunnelling and crapping).
Severe itching at night
Itching can occur in one or
more areas.
Scratching can lead to
bacterial infection by Staph.
Aureus or Streptococcus
Scabies rash
Crusted Scabies (Norwegian
Scabies)
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Normal infection: 12-15 mites
Crusted infection: millions of mites
Immunocompromised patients,
elderly, and paralyzed (unable to
itch or scratch).
45% of cases have advanced AIDS.
Vesicles and thick crusts over skin.
Very contagious and hard to treat.
Crusted scabies on feet
Mange
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Caused by other varieties of
Sarcoptes scabiei in some cases.
Sarcoptic mange affects dogs,
wolves, coyotes, red foxes,
pigs, dogs, horses, and cattle.
Intense itching and hair loss.
Sarcoptes scabiei are host
specific, won’t survive long
on improper host.
Mice and cats afflicted by
different genera; Notoedres
Mange
Treatment
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Acaricides (substances that kill mites)
Scabicides (substances that kill scabies mites)
Topical creams
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Oral medication
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5% permethrin, 1% lindane, 0.05% malathion, 10%
crotamiton, 25% benzyl benzoate.
Applied for 8-12 hours, then removed
Ivermectin (200µg/kg)
Animal treatment
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Ivermectin or insecticides
References
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Elmer, N., N. Glenn, S. Gerhard, and M. Austin. 1989. Parasitology: The Biology of
animal Parasites. Sixth edition. Lea and Febiger, Philadelphia.
Karthikeyan, K. 2009. Crusted scabies. Indian Journal of Dermatology Venereology &
Leprology 75:340-347.
Tjioe, M. and W. Vissers. 2008. Scabies outbreaks in nursing homes for the elderly.
Drugs & Aging 25:299-306.
Walton, S. F. 2010. The immunology of susceptibility and resistance to scabies.
Parasite Immunology 32:532-540.
Walton, S. F. and B. J. Currie. 2007. Problems in diagnosing scabies, a global disease in
human and animal populations. Clinical Microbiology Reviews 20:268-+.
Walton, S. F., S. Pizzutto, A. Slender, L. Viberg, D. Holt, B. J. Hales, D. J. Kemp, B. J.
Currie, J. M. Rolland, and R. O'Hehir. 2010. Increased Allergic Immune Response to
Sarcoptes scabiei Antigens in Crusted versus Ordinary Scabies. Clinical and Vaccine
Immunology 17:1428-1438.