PARASITIC MITES OF HUMANS
M ichael F. Potter, Extension Entomologist
M ites are very small arthropods which are closely
Persons walking in chigger-infested areas can be
related to ticks. M ite larvae have six legs whereas the
protected by treating clothing (cuffs, socks, waistline,
nymphal and adult stages have eight. M ost species of
sleeves) or exposed skin with tick repellents. Some
mites are pests of agricultural crops. However, certain
repellents should only be used on clothing; and it is
types of mites are parasitic on humans.
important to follow label directions. People who suspectthey may have been attacked by chiggers should take a
soapy bath immediately and apply antiseptic to anywelts. A local anesthetic will provide temporary relief
Chiggers are the larvae of a
family of mites that aresometimes called red bugs.
Regular mowing and removal of weeds and brush make
The adults are large, red mites
areas less suitable for chiggers and their wild hosts.
often seen running over
M owing also enhances penetration and performance of
miticides, should they be required. Chigger populations
Chiggers are extremely small
can be further reduced by treating infested areas with
(0.5 mm) and are difficult to
residual miticides. Applications should be thorough but
see without magnification. The
restricted to areas frequented and suspected of being
six-legged larvae are hairy
! Human Scabies
encountered outdoors in low, damp places wherevegetation is rank and grass and weeds are overgrown.
Some species also infest drier areas, however, making it
Sarcoptes scabei, infest the skin
difficult to predict where an infestation will occur.
of a variety of animals including
humans. The types of Sarcoptes
Chiggers overwinter as adults in the soil, becoming
inhabiting the skin of mammals
active in the spring. Eggs are laid on the soil. After
are all considered forms of
hatching, the larvae crawl about until they locate and
Sarcoptes scab ei a n d can
attach to a suitable host. The larvae do not burrow into
exchange hosts to some degree.
the skin, but inject a salivary fluid which produces a
(For example, Canine scabies can
hardened, raised area around them. Body fluids from the
be temporarily transferred from
host are withdrawn through a feeding tube. Larvae feed
dogs to humans, causing itching
for about 4 days and then drop off and molt to
and lesions on the waist, chest
nonparasitic nymphs and adults. Chiggers feed on a
variety of wild and domestic animals, as well as humans.
The life cycle (from egg to egg) is completed in about 50
Human scabies mites are very small and are rarely seen.
They commonly attack the thin skin between the fingers,the bend of the elbow and knee, the penis, breasts, and
M ost people react to chigger bites by developing reddish
the shoulder blades. The mites burrow into the skin,
welts within 24 hours. Intense itching accompanies the
making tunnels up to 3 mm (0.1 inch) long. W hen they
welts, which may persist for a week or longer if not
first burrow into the skin, the mites cause little irritation,
treated. Bites commonly occur around the ankles,
but after about a month, sensitization begins. A rash
waistline, armpits, or other areas where clothing fits
appears in the area of the burrows and intense itching is
tightly against the skin. Besides causing intense itching,
chigger bites that are scratched may result in infection
and sometimes fever. Chiggers in North America are not
Scabies mites are transmitted by close personal contact,
known to transmit disease.
usually from sleeping in the same bed. Bedridden
individuals in institutions (e.g., nursing homes) may also
source. Their bites cause moderate to intense itching and
pass the mites from caregiver to patient. The adult
irritation. Rodent and bird mites are very tiny, but
fertilized female mite is usually the infective life stage.
usually can be seen with the naked eye. They are about
She adheres to the skin using suckers on her legs and
the size of the period at the end of this sentence.
burrows into the skin where she lays her oval eggs. In 3to 5 days these eggs hatch into larvae and move freely
The first step in controlling bird or rodent mites is to
over the skin. Soon they transform into nym phs and
eliminate the host animals and remove their nesting
reach maturity 10 to 14 days after hatching.
sites. Often, the nests will be found in the attic, aroundthe eaves and rafters, or in the gutters or chimney.
A scabies infestation should be handled as a medical
Gloves should be used when handling dead animals. A
problem and is readily diagnosed and treated by most
respirator should also be worn when removing nest
physicians. (Confirmation requires isolating the mites in
materials to avoid inhaling fungal spores and other
a skin scraping.) The first step to control a scabies
potential disease-producing organisms associated with
infestation usually involves softening the skin with soap
and water to make sure the pesticide treatments canpenetrate well. An evening bath followed by overnight
After nests are removed, the areas adjacent to the nest
treatment works best. A total body (neck- down)
should be sprayed or dusted with a residual insecticide
application of topical pesticide medication should
such as those products labeled for flea control. Space or
remain for 8-12 hours before showering in the morning.
ULV treatments with non-residual materials (e.g.,
Commonly used products include lindane (Kwell (tm)),
synergized pyrethrins) can be used in conjunction with
permethrin (Elimite (tm)) and crotamiton (Eurax (tm )).
residual sprays. Space treatm ents are especially useful
Follow directions on the product package carefully.
when the mite infestation has dispersed widely from thenesting site. In this case, more extensive treatment with
Because the sym ptoms of scabies mite infestations are
residual and non-residual insecticides may also be
delayed by about a month, other members of the
necessary in other areas of the structure where mites are
household besides those showing symptoms may be
observed. A vacuum cleaner or cloth moistened with
harboring the mites. It is important that everyone in the
alcohol can be used to eliminate mites crawling on open
infected family or living group go through the treatment
regime. A second treatment may be necessary toeliminate an infestation of scabies m ites, but patientsshould avoid overzealous pesticide treatment since
itching may persist for a week or more after treatmentand does not necessarily indicate treatment failure.
Scabies mites cannot live off of a human host for morethan 24 hours. Therefore, insecticide treatment ofpremises is not warranted. It is recommended, however,that coincident with treatment, the clothing and beddingfrom infested individuals be washed in hot water or drycleaned.
! Bird and Rodent Mites
Parasitic mites that occasionally infest buildings areusually associated with wild or domestic birds orrodents. Bird and rodent mitesnormally live on the host or intheir nests, but migrate to otherareas of the structure when theanimal dies or abandons thenest. Rodent mites often becomea nuisance after an infestationof mice or rats has beenelim inated. People usuallybecome aware of the problemwhen they are attacked by mitessearching for an alternate food
ESH position statement The metabolic syndrome in hypertension: European society ofhypertension position statementJosep Redon, Renata Cifkova, Stephane LaurentPeter NilssoKrzysztof NarkiewiczSerap Erdineand Giuseppe Mancia, on behalf ofthe Scientific Council of the European Society of Hypertension The metabolic syndrome considerably increases the risk of compelling indications are present for its use. If a
ZYPREXA® NAME OF THE MEDICINE ZYPREXA® (olanzapine). ZYPREXA® Zydis® (olanzapine). Chemically, olanzapine is 2-methyl-4-(4-methyl-1-piperazinyl)-10H-thieno[2,3-b] [1,5]benzodiazepine and its empirical formula is C17H20N4S. Olanzapine is a yellow crystalline solid, practically insoluble in water with a molecular weight of 312.44. The CAS number for olanzapine is 132539-06-1.