Ticks, Mites and Associated Pathogens
Overview:
• Characteristics of the subclass Acari (ticks
and mites)
• Metastigmatid mites = ticks
• Ticks and tick-borne pathogens
• All other mites….
• Mites and mite-borne pathogens
1
Ticks and Mites (Subclass Acari)
1. Class Arachnida (Also includes spiders and
scorpions
2. Characteristics of Acari (mites and ticks):
a. sac-like, unsegmented body
b. highly specialized mouthparts, capitulum w/
hypostome
c. phytophagous, predatory, parasitic
d. larvae 6 legs, nymph & adult 8 legs
e. 4-stage life cycle, egg-larva-nymph-adult
2
Ticks and Mites - Classification
Class Arachnida
Subclass Acari
Order Ixodida (= Metastigmata) (ticks)
Order Mesostigmata (free-living,
predaceous, and parasitic mites)
Order Prostigmata (chiggers, follicle mites)
Order Astigmata (house dust, storage & scabies
mites)
3
Ticks - Classification
Class Arachnida
Ticks (3 families):
Ixodidae
Argasidae
Subclass Acari
Superorder
Parasitiformes
Nuttalliellidae
Order
4
Source: http://tolweb.org/tree/phylogeny.html
Mites - Classification
Class Arachnida
Subclass Acari
Mesostigmatid
Mites
Superorder
Parasitiformes
Order
5
Source: http://tolweb.org/tree/phylogeny.html
Mites – Classification (2)
Class Arachnida
Prostigmatid and
Astigmatid Mites
Subclass Acari
Superorder
Acariformes
6
Source: http://tolweb.org/tree/phylogeny.html
Ticks and Mites - Classification
• Recent validation of Acari suborders (ticks
are ticks and mites are mites)
• Recent reorganization within the ticks
J. S. H. Klompen, William C. Black IV, James E. Keirans, and Douglas E.
Norris. 2000. Systematics and Biogeography of Hard Ticks, a Total
Evidence Approach. Cladistics 16, 79–102.
Ivan G. Horak, Jean-Louis Camicas and James E. Keirans. 2002. The
Argasidae, Ixodidae and Nuttalliellidae (Acari: Ixodida): a world list of valid
tick names. Experimental and Applied Acarology 28: 27–54.
7
8
TICKS
MITES
9
TICKS
Characteristics of Ixodida (ticks) - approx. 900
species
a. largest of acarines - larger than mites
b. toothed hypostome
c. Haller's organ (sensory pit on tarsi of first pair
of legs)
d. absence of claws on palps
e. evolved as parasites of reptiles, adaptation to
mammals associated with general reduction in
body size
Tick Families: Ixodidae - Hard Ticks, Argasidae –
Soft Ticks, Nuttalliellidae - rare, S. Africa (single
10
species)
Soft tick
Hard tick
(Family Argasidae)
11
(Family Ixodidae)
Family Ixodidae Hard Ticks (approx. 683 species,
12 genera)
Features:
a. sexual dimorphism, male - enlarged scutum,
female - shield
b. mouthparts (capitulum) visible dorsally
c. feed only once during each stage, often
diurnal, males show little size increase
d. range parasites, questing from vegetation,
one large egg batch
12
Female hard tick
Male hard tick
13
Typical Life History of Hard Ticks
(most three-host):
a. One-Host: Rhipicephalus (Boophilus)
annulatus (Texas Cattle Fever Tick), all stages
on same host, but leave host to molt, control
using pasture rotation
b. Three-Host: Dermacentor variabilis
(American Dog Tick), each stage uses a
different host - larva on small rodents, nymph
on larger mammal, adult on another large
mammal. Other three host: Rhipicephalus
sanguineus (Brown Dog Tick) Amblyomma
americanum (Lone Star Tick)
14
Description of medically-important hard ticks:
Genus
Approx. # Species
World
U.S.
Amblyomma
100
Dermacentor
31
Hyalomma
30
Nosomma
1
Rhipicephalus
68
(includes Boophilus)
Haemaphysalis 155
Ixodes
217
Margaropus
2
Bothriocroton
5
7
7
0
0
3
2
40
0
0
Distribution
worldwide, mostly tropical
worldwide
Africa, Asia
India, SE Asia
Ethiopian / tropicopolitan
worldwide
worldwide
southern, east Africa
Austrailia
15
Genus Ixodes: Largest genus of hard ticks
• Ixodes ricinus/persulcatus complex - Lyme Disease,
HGE
• I. ricinus (European Sheep tick) through Europe,
Turkey, Iran
• I. persulcatus (Taiga tick) Eurasian
• I. scapularis (Black-legged tick) eastern US
• I. pacificus (Western Black-legged tick) western US.
• I. holocyclus Australia (tick paralysis)
• I. rubicundus (Karoo tick) South Africa
16
Genus Haemaphysalis: Small, both sexes
similar, important in enzootic cycles
• H. leporispalustris (Rabbit tick) western
hemisphere distribution (important maintenance
vector for tularemia and RMSF)
Genus Hyalomma: Large unornamented ticks
•
H. marginatum Russian states, southern
Europe (Crimean-Congo hemorrhagic fever)
17
Genus Rhipicephalus: African origin, but several
species worldwide in the tropics (now includes
previous species of Boophilus, non-ornamented,
one-host ticks)
• R. sanguineus (Brown Dog tick) cosmopolitan
distribution (RMSF, boutonneuse fever)
• R. (Boophilus) annulatus (Cattle Fever tick)
southern US, Mexico (Texas Cattle fever, field
rotation for control)
• R. (Boophilus) microplus (Southern cattle tick)
Australia, Mexico, S. America
18
Genus Dermacentor: Ornate ticks
• D. variabilis (American dog tick) eastern US,
Canada, Mexico (tularemia, RMSF)
• D. andersoni (Rocky Mountain wood tick)
western North America (tularemia, RMSF,
Colorado tick fever)
• D. albipictus (Winter tick) across Canada
• D. occidentalis (Pacific coast tick) Oregon,
California
19
Genus Amblyomma: Large ornate ticks
• A. americanum (Lone Star tick) central/eastern
US - S. American (RMSF, tularemia)
• A. cajennense (Cayenne tick) Texas, S. America,
Caribbean
• A. hebraeum (Bont tick) S. Africa
20
Family Argasidae Soft Ticks
(183 species, 4 genera)
Features:
a. slight sexual dimorphism, only slight
swelling from feeding
b. scutum absent
c. capitulum not visible dorsally
d. palpi leg-like and flexible
e. intermittant "rapid" feeder, nocturnal
f. sometime several nymphal instars, some
non-feeding larvae
g. lair parasites, several egg batches,
dry adverse environments
21
Soft tick
Hard tick
(Family Argasidae)
22
(Family Ixodidae)
Typical life history of soft ticks:
a. Many-host cycle. Often one larval host and
several nymphal and adult hosts. Adult female
lays eggs after each feeding
Argas persicus (Fowl Tick) chicken houses,
bird nests, cosmopolitan
Ornithodoros moubata (African Relapsing
Fever Tick) feeds on sleeping humans,
southern Africa
Otobius megnini (Spinose Ear Tick) adult nonfeeding, nymph problem
23
Description of medically-important soft ticks:
Genus
Approx. # species
Distribution
Argas
55
worldwide
Ornithodoros
38
worldwide
Otobius
3
western hemisphere
Carios
84
worldwide
24
Genus Argas: most nocturnal bird-associated
• A. persicus (Fowl tick) cosmopolitan (economic
importance, painful bite)
• A. arboreus east, S. Africa (arbovirus vector)
25
Genus Ornithodoros: Reservoirs and vectors of
relapsing fever
• O. moubata (African Relapsing Fever tick) S.
Africa (species complex) numerous species
Genus Otobius: Adults do not feed
• O. megnini (Spinose ear tick) western
hemisphere, Africa, India (nymphal infestations
in ears)
26
Tick Sampling
a.
b.
c.
observation on hosts and premises
Dragging/flagging
CO2 - baited traps
Tick Control
a.
b.
Natural predators
Repellents/toxicants for human use
I.
DEET (apply to skin)
II.
Pyrethroids (apply to clothing)
27
• Cultural/mechanical control
I.
II.
III.
remove harborage for hosts/ticks
destroy hosts
pasture rotation (one-host only)
• Resistant livestock
•
Anti-tick vaccine
•
Chemical control on animal host, or
acaricide in habitat
28
AVOIDING TICKS
• Wear light-colored clothing to allow you to see ticks
that are crawling on your clothing.
• Tuck your pants legs into your socks so that ticks
cannot crawl up the inside of your pants legs.
• Apply repellants to discourage tick attachment.
Repellents containing permethrin can be sprayed on
boots and clothing, and will last for several days.
Repellents containing DEET (n, n-diethyl-mtoluamide) can be applied to the skin, but will last
only a few hours before reapplication is necessary.
Use DEET with caution on children. Application of
large amounts of DEET on children has been
associated with adverse reactions.
29
AVOIDING TICKS - II
• Conduct a body check upon return from potentially
tick-infested areas by searching your entire body for
ticks. Use a hand-held or full-length mirror to view all
parts of your body. Remove any tick you find on your
body.
• Parents should check their children for ticks,
especially in the hair, when returning from potentially
tick-infested areas. Additionally, ticks may be carried
into the household on clothing and pets. Both
should be examined carefully.
30
Tick Removal:
1. Use fine-tipped
tweezers or shield your
fingers with a tissue,
paper towel, or rubber
gloves. When possible,
persons should avoid
removing ticks with bare
hands.
Removal of an embedded tick
using fine-tipped tweezers.
2. Grasp the tick as
close to the skin
surface as possible
and pull upward with
steady, even pressure.
Do not twist or jerk the
tick; this may cause the
mouthparts to break off
and remain in the skin.
31
3. Do not squeeze, crush, or puncture the body of the
tick because its fluids (saliva, body fluids, gut
contents) may contain infectious organisms.
4. After removing the tick, thoroughly disinfect the
bite site and wash your hands with soap and water.
5. Save the tick for identification in case you become
ill. This may help your doctor make an accurate
diagnosis. Place the tick in a plastic bag and put it in
your freezer. Write the date of the bite on a piece of
paper with a pencil and place it in the bag.
32
33
34
Haemaphysalis
bremneri
mouthparts,
showing toothed,
sawlike
hypostome.
Photograph copyright 2001 Steve Barker
35
Photograph copyright 2001 Steve Barker
Otobius megnini
36
Medical Importance of Ticks
1.
Dermatosis - inflammation, itching ,
swelling at site of bite
2.
Exsanguination - anemia can result from
heavy infestation
3.
Otoacariasis - auditory canal infestation,
poss. secondary infection
4.
Predispose to myiasis and infection
5.
Tick paralysis (envenomization)
6.
Pathogen transmission (virus, rickettsia,
bacteria, spirochaete, protozoa, filarial
worms)
37
Factors Accounting for High Vector
Potential of Ticks
1.
Persistent hematophagous feeders
2.
Relatively slow feeding time allows time for
pathogen transfer
3.
Typically have a wide host range
4.
Longevity increases chances of acquiring and
transmitting a pathogen
5.
Transovarial transmission of some pathogens
6.
Few natural enemies, highly sclerotized
(resistant to environmental stress)
7.
High reproductive potential - up to 18,000 eggs
and parthenogenesis in some species
38
Non-viral Tick-Borne Pathogens
•
•
•
•
•
•
•
•
•
Lyme Disease (Borrelia burgdorferi)
Babesia microti (malaria-like)
Ehrlichia species
Relapsing fever (Borrelia species)
Tularemia (Francisella tularensis)
RMSF (Rickettsia rickettsii)
Tick typhus (Rickettsia sp.)
Heartwater (Cowdria ruminantium)
Anaplasmosis (Anaplasma sp.)
39
Some Tick-Borne Pathogens
• Human monocytic ehrlichiosis (HME), caused by
Ehrlichia chaffeensis a new monocytotropic ehrlichia,
was discovered in 1986 and human granulocytic
ehrlichiosis (HGE), caused by the HGE agent (newly
named Anaplasma phagocytophilum), a new
granulocytotropic ehrlichia, was discovered in 1994.
• In 1999 another granulocytotropic ehrlichia, E. ewingii
which was previously known as a canine pathogen
has been recognized as human pathogen. E.
sennetsu (renamed to Neorickettsia sennetsu) is
another monocytotropic Ehrlichia sp. and the first
human pathogen discovered in Japan in the 1950’s
and recently found in Malaysia.
40
This phylogram is constructed based on 16S rRNA sequences of these species.
Nomenclature has been changed from original names based on 16S rRNA
sequences which divided them into four genera groups.
Family Anaplasmataceae now contains four genera: Ehrlichia, Anaplasma,
41
Neorickettsia, and Wolbachia.
Ehrlichiosis and Anaplasmosis
• Small gram-negative bacteria that grow in
membrane-bound vacuoles in leukocytes or platelets
• Typically 1-3 um cocci
• Different species of Ehrlichia infect different types of
host cells
• Not all species transmitted by arthropods
• HME (human monocytic ehrlichiosis), E. chaffeensis
• HGE (human granulocytic ehrlichiosis), (A.
phagocytophila)
• HGE overlap with Lyme disease - both transmitted by
Ix. scapularis complex members in US
42
Ehrlichia chaffeensis is principally transmitted by the lone star tick (Amblyomma americanum).
White-tailed deer are a major host of lone star ticks and appear to represent one natural
reservoir for E. chaffeensis. Antibody to E. chaffeensis has been found throughout deer
populations in the southeastern and midwestern United States, and the organism has been
43
cultured from deer blood. (CDC)
Cases of HME are predominantly found in
the South and south-central regions where
the suspect vector, the Lone Star tick
(Amblyomma americanum) is present.
Amblyomma americanum
Lonestar tick
Associated with
E. chaffeensis
transmission (HME)
44
Average annual incidence of reported human
monocytic ehrlichiosis (HME) by county, using 1995
45
population census data.
The HGE agent has been associated with the blacklegged tick (Ixodes scapularis)
in the northeastern and upper midwestern United States. The western
blacklegged tick (Ixodes pacificus) is a vector in northern California. Ixodes
ricinus has been shown to be a vector of A. phagocytophila in Europe. Deer, elk,
46
and wild rodents are likely reservoirs.
Ixodes pacificus - western black-legged tick
Cases of HGE have been reported primarily in the
Northeast and Midwest regions and are associated
with the bite of deer ticks (Ixodes scapularis). A
few cases on the Pacific coast are associated with
the related species, Ixodes pacificus.
Ixodes scapularis - black-legged deer tick
47
Average annual incidence of reported human
granulocytic ehrlichiosis (HGE) by county, using
1995 population census data.
48
Distribution of the Tick Vectors of Ehrlichia
and Anaplasma in the United States
49
Ehrlichiosis - Epidemiology
• During 1986 to 1997, health departments and other
diagnostic laboratories reported over 1200 cases of
human ehrlichiosis to CDC.
• Approximately two-thirds were cases of HME. CDC
compiles the number of cases reported by the state
health departments.
• Ehrlichiosis is a nationally notifiable disease;
however, not all state health departments have
reported cases of ehrlichiosis to CDC.
50
Reported Cases of Ehrlichiosis in the United States51
Approximate Seasonal Distribution of HGE in the United States
52
States where Ehrlichiosis is a notifiable disease (green)
53
Lyme Disease
• Lyme disease was named in 1977 when arthritis was
observed in a cluster of children in and around Lyme,
Connecticut.
• Other clinical symptoms and environmental conditions
suggested that this was an infectious disease probably
transmitted by an arthropod.
• Further investigation revealed that Lyme disease is
caused by the spirochete bacterium, Borrelia burgdorferi.
• These bacteria are transmitted to humans by the bite of
infected deer ticks and cause more than 16,000 infections
in the United States each year.
54
Lyme Disease - Vectors
• Black-legged ticks (Ixodes scapularis) are responsible
for transmitting Lyme disease bacteria to humans in the
northeastern and north-central United States.
• On the Pacific Coast, the bacteria are transmitted to
humans by the western black-legged tick (Ixodes
pacificus).
• Ixodes ticks are much smaller than common dog and
cattle ticks. In their larval and nymphal stages, they are
no bigger than a pinhead.
• Ticks feed by inserting their mouths into the skin of a
host and slowly take in blood.
• Ixodes ticks are most likely to transmit infection after
feeding for two or more days.
55
56
Ixodes scapularis
female, male, nymph, larva
White-tailed
deer important
vertebrate host
of adult ticks
57
58
Borrelia sp. Transmission
Greatest
risk
59
Lyme Disease - Risk
• In the United States, Lyme disease is mostly localized
to states in the northeastern, mid-Atlantic, and upper
north-central regions, and to several counties in
northwestern California.
• In 1999, 16,273 cases of Lyme disease were reported
to the Centers for Disease Control and Prevention
(CDC).
• Ninety-two percent of these were from the states of
Connecticut, Rhode Island, New York, Pennsylvania,
Delaware, New Jersey, Maryland, Massachusetts,
and Wisconsin.
• Outdoor exposure - recreational, professional.
60
61
62
Year
63
Month of Lyme disease onset for reported cases, United States - 1992-1998.
64
Lyme Disease - Symptoms
• Lyme disease most often presents with a
characteristic "bull's-eye" rash, erythema migrans,
accompanied by nonspecific symptoms such as fever,
malaise, fatigue, headache, muscle aches (myalgia),
and joint aches (arthralgia).
• The incubation period from infection to onset of
erythema migrans is typically 7 to 14 days but may be
as short as 3 days and as long as 30 days.
• Some infected individuals have no recognized illness
(asymptomatic infection determined by serological
testing), or manifest only non-specific symptoms such
as fever, headache, fatigue, and myalgia.
65
Lyme spirochete
Borrelia burgdorferi
400x
ECM erethyma
chronicum
migrans
(bull’s eye rash)
66
Lyme Disease - Treatment/Control
• Antibiotic treatment for 3-4 weeks with doxycycline or
amoxicillin is generally effective in early disease.
• Cefuroxime axetil or erythromycin can be used for persons
allergic to penicillin or who cannot take tetracyclines.
• Later disease, particularly with objective neurologic
manifestations, may require treatment with intravenous
ceftriaxone or penicillin for 4 weeks or more, depending on
disease severity.
• In later disease, treatment failures may occur and
retreatment may be necessary.
67
Babesiosis
• Babesiosis is caused by hemoprotozoan parasites of the
genus Babesia.
• While more than 100 species have been reported, only a
few have been identified as causing human infections.
• Babesia microti and Babesia divergens have been identified
in most human cases, but variants (considered different
species) have been recently identified.
• Little is known about the occurrence of Babesia species in
malaria-endemic areas where Babesia can easily be
misdiagnosed as Plasmodium.
68
Babesiosis - Life Cycle
• Babesiosis is transmitted by ixodid (hard-bodied) ticks.
Ticks become infected by feeding on an infected vertebrate
animal (rodents, cattle, wild animals) or transovarially (ticks
thus can be vectors as well as reservoirs), depending on
the Babesia species.
• In the ticks, the parasites develop and multiply.
Transmission to the next vertebrate host occurs during a
subsequent blood meal of the tick.
• Inside the vertebrate host, the parasites directly invade the
erythrocytes (without the exo-erythrocytic liver stage
required by human malaria parasites), where they undergo
successive cycles of multiplication and reinvasion.
• The cycle is closed when the infected blood is ingested by a
tick feeding on the mammalian host. Babesia can also be
acquired by transfusion of blood or blood products.
69
Babesiosis - Geographic Distribution
• Worldwide, but little is known about the prevalence of
Babesia in malaria-endemic countries, where misdiagnosis
as Plasmodium probably occurs.
• In Europe, most reported cases are due to B. divergens and
occur in splenectomized patients.
• In the United States, B. microti is the agent most frequently
identified (Northeast and Midwest), and can occur in nonsplenectomized individuals.
• Two variants, arguably different species, have been
reported in the U.S. states of Washington and California
(WA1- type and related parasites) and Missouri (MO1).
70
Tick-Borne Pathogens
•
•
•
•
•
•
•
•
•
Lyme Disease (Borrelia burgdorferi)
Babesia microti (malaria-like)
Ehrlichia species
Relapsing fever* (Borrelia species)
Tularemia (Francisella tularensis)
RMSF (Rickettsia rickettsii)
Tick typhus (Rickettsia sp.)
Heartwater (Cowdria ruminantium)
Anaplasmosis (Anaplasma sp.)
71
*soft tick
Rocky Mountain Spotted fever
a. pathogen Rickettsia rickettsii
b. Nearctic and Neotropical, first described in US
c. human disease, now most common in eastern US,
human encroachment
d. headache, lumbar ache, malaise, 2-5 day
incubation, antibiotic treatment
e. transmission by bite, trans-stadial and TOT
f. D. variabilis eastern, D. andersoni western,
Amblyomma cajennense neotropical
72
Characteristic spotted rash of latestage Rocky Mountain spotted fever
on legs of a patient, ca. 1946
73
Dermacentor variabilis
American dog tick
Dermacentor andersoni
Rocky Mountain wood tick
74
Figure 9. Reported cases of Rocky Mountain spotted fever in
the United States, 1942-1996.
75
Figure 10. Seasonal distribution of reported cases of Rocky
Mountain spotted fever, 1993-1996.
76
Figure 11. Number of reported cases of Rocky Mountain
spotted fever by state and region, 1994-1998.
77
Tick-borne Viruses
1. More than 100 arboviruses associated
with ticks; 116 tick species, 32 argasid, 84
ixodid.
2. Many based only on isolation of virus,
disease potential unknown
3. Most important all exist as zoonoses, and
TOT occurs in some
78
Colorado tick fever (Reoviridae, genus Orbivirus)
a. focal zoonosis in Rocky Mountain states and
South Dakota of US, and western Canada,
overwinters in nymph
b. main vector to humans is Dermacentor andersoni,
no TOT, other zoonotic vectors
c. reservoir hosts - rodents, squirrels, porcupines
d. disease is dengue-like, 3-6 day incubation in
humans, severe in children
79
Tick-borne encephalitides
(Flaviviridae, genus Flavivirus), two forms
a. Russian Spring Summer encephalitis (far eastern form)
I. taiga forest in E. Russia and NE China
II. vector is Ixodes persulcatus
b. Tick-Borne encephalitis (western form)
I. coniferous and temperate deciduous forests
II. vector is I. ricinus
c. Overlap of tick species in western Russia, both forms of
virus present, other ticks involved in focal transmission,
TOT in ticks, "holiday" disease, tick bite or drinking milk of
infected goat
80
Kyasanur Forest disease (genus Flavivirus)
a. Southern India, disease discovered following monkey
deaths, and human illness/death
b. vector is Haemaphysalis spinigera (H. turturis - zoonotic
cycle)
c. human contact in forest, intrusion in foci of infection
d. fever, headache, severe muscle pain - diphasic - cough,
GI disturbance, prolonged recovery, 5% mortality
81
Crimean-Congo hemorrhagic fever
(Bunyaviridae, genus Nairovirus)
a. Russian states, Asia, Africa, Europe - first seen in
Russian soldiers
b. 27 tick taxa associated with zoonotic maintenance, TOT
in some species
c. human epidemics associated with Hyalomma
marginatum and other sp. of Hyalomma
d. infection via bite, or crushing tick on skin
e. acute febrile illness with hemorrhagic symptoms
82
Others:
Louping Ill virus
I. ricinus
sheep, UK
Omsk Hemorrhagic Fever virus
Dermacentor sp. and Ixodes sp.
Siberia
Powassan Encephalitis virus
Dermacentor sp. and Ixodes sp.
US
83
MITES
Usually less than 1 mm long, life cycle: egg-larvanymph-adult, 1-3 nymphal stages
1. oviposition - usually egg, but some ovoviviparous
2. egg -- adult, 8 days to several weeks, average 4
weeks
Abdomen joined to cephalothorax, no segmentation
1. Typical 3 legs - larva, 4 legs - adult, but reduction
in some species
2. Chelicerae for tearing or piercing in parasitic
species
84
MITES
Free-living, predaceous and parasitic - endo/ecto
Skin damage to livestock, as much as $5 million
/year in economic damage
Effects on humans and animals:
1.
2.
3.
4.
dermatitis or other tissue damage
loss of blood or other tissue fluids
transfer of pathogenic agents
cause of strong allergic reactions
85
ACARIASIS - infestation with mites
Possible sites of infestation:
• external, inner and middle ear
• respiratory passages and lungs
• nasal passages
• lymphatic tissue
86
MITES
Order Mesostigmata
A. Relatively large mites, 0.2 - 2.0 mm length
B. Pair of stigmata located behind and lateral to
third coxa, associated with peritremes
C. Many are predatory, biocontrol uses
D. Not host specific, human host unusual but will
cause skin disorders
(Laelaps sp., Ornithonyssus sp.)
87
Mesostigmatid Mite
88
MITES
Order Prostigmata
A. Heterogenous group, weakly sclerotized, 0.1 10.0 mm in length
B. Stigmata present, usually at base of chelicerae,
difficult to see
C. More than 50 families in suborder, some medically
important
(Demodex sp., Trombiculid mites)
89
90
MITES
Order Astigmata
A. Stigmata and tracheae absent, integumental
respiration
B. Small (0.2-1.2mm), thin-skinned mites without
obvious shields
C. Coxae sunk into ventral body wall (epimeres)
D. Palps are 2-segmented and chelicerae pincer-like
(Sarcoptes sp., Dermatophagoides sp., Tyroglyphus sp.)
91
Sarcoptes scabei
92
MITES - Control
Sampling
1. Removal from outside host, with wash
2. Skin scraping for intradermal forms
3. Drag similar to tick flagging
93
MITES - Control
Direct host treatment
a. for human scabies, repeated treatments with
ointments containing sulfur, benzyl benzoate,
thiabendazole, or an approved insecticide
(permethrin) - lindane resistance
b. injection of products such as Ivermectin
c. insecticidal dipping for domestic animals
94
MITES - Control
•
Premise spray
a.
•
Repellent/Toxicant
a.
b.
•
spray roosts for chicken/fowl mites
permethrin
apply to socks, bottom of pant legs
Quarantine
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Mite-Borne Pathogens
• Rickettsialpox (Rickettsia akari)
• Scrub typhus (Orientia tsutsugamushi)
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Rickettsialpox
Rickettsia akari
Liponyssoides mite vector
House mice, rats - vertebrate hosts in urban areas
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Chiggers
• Chiggers, also known as "redbugs, jiggers or harvest mites",
are the immature stages of a tiny red mite.
• They inhabit areas of tall grass, associated with low, wet
spots, ponds and stream banks, wild berry patches and
forest underbrush.
• The larvae attach themselves to the clothing of people or to
the fur of passing animals. Before settling down to feed,
chiggers move to a constriction such as sock tops, waist
bands or armpits.
• Feeding chiggers inject a salivary fluid which dissolves the
host's cells, then suck up the liquefied tissue. Within a few
hours, small, reddish, intensely itching welts appear.
• These bites may continue to itch for several days up to two
weeks after the chigger is dislodged.
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US distribution of chiggers - other areas
also have focally high populations
The Culprit
Larval
chigger mite
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Scrub typhus
(Orientia tsutsugamushi)
Vector - larval Leptotrombidium mites\
Reservoir - mites via TOT, transitory
rodent infections
Distribution - SE Asia and islands of
Indian Ocean and SW Pacific, coastal
North Queensland, Australia
Exposure - outdoor recreation or
occupational exposure - disturbed
habitat
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Chigger Protection
• Stay out of areas where chiggers are likely to be present
including woodlots, pastures, roadside ditches or other
areas with tall grasses and weeds. Chiggers are
especially common in moist low-lying areas.
• Wear loose-fitting clothing and avoid sitting or reclining
on the ground when camping, picnicking or working
outdoors.
• Apply a repellent containing DEET (N,N-diethyl-metatoluamide) to shoes, socks and trousers before entering
chigger-infested areas. Caution: some individuals may
be sensitive to DEET. Always read and follow label
directions.
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Chigger Protection - II
• Immediately after possible exposure to chiggers take a
bath, thoroughly scrubbing the body with hot soapy water.
This will kill or dislodge many of the chiggers.
• When bites begin to itch, apply rubbing alcohol, followed
by one of the non-prescription local anesthetics. A baking
soda paste, calamine lotion or product such as "After-Bite"
also will help reduce discomfort.
• Avoid scratching bites since this only increases irritation
and may lead to secondary infection of the bite.
• Where chiggers are a problem in landscapes, keep lawns
and shrubbery well manicured especially in areas adjacent
to dwellings. Eliminate tall grasses and weeds. Chiggers
also can be reduced by spraying infested foliage with
carbaryl (Sevin), chlorpyrifos (Dursban) or diazinon. 104
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Sarcoptes scabei
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Scabies
• Scabies is an infestation of the skin with
the microscopic mite Sarcoptes scabei.
Infestation is common, found worldwide,
and affects people of all races and
social classes.
• Scabies spreads rapidly under crowded
conditions where there is frequent skinto-skin contact between people, such as
in hospitals, institutions, child-care
facilities, and nursing homes.
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Scabies - Symptoms
• Pimple-like irritations, burrows or rash of
the skin, especially the webbing between
the fingers; the skin folds on the wrist,
elbow, or knee; the penis, the breast, or
shoulder blades.
• Intense itching, especially at night and
over most of the body.
• Sores on the body caused by scratching.
These sores can sometimes become
infected with bacteria.
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Scabies - Infestation
• By direct, prolonged, skin-to-skin contact
with a person already infested with scabies.
Contact must be prolonged (a quick
handshake or hug will usually not spread
infestation). Infestation is easily spread to
sexual partners and household members.
Infestation may also occur by sharing
clothing, towels, and bedding.
• People with weakened immune systems
and the elderly are at risk for a more severe
form of scabies, called Norwegian or
crusted scabies.
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DEMODEX
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Demodex - the follicle mites
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Dermatophagoides
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House Dust Mites - Dermatophagoides
• The term 'house dust mites' is used originally to
refer to those mites belonging to
Pyroglyphidae. At present, the term 'dust mites'
is widely used instead and this is in reference
to all pyroglyphid and nonpyroglyphidites that
are implicated in dust borne respiratory allergy.
• House dust mites cause 25% of all allergies
and 50% of all asthmatic diseases are
traceable to house dust mites
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Areas at highest risk for dust mite problems.
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Ticks, Mites and Associated Pathogens
Summary:
• Characteristics of the order Acari (ticks and mites)
• Metastigmatid mites = ticks
• MANY tick-borne pathogens…
• Mesostigmatid mites, prostigmatid mites and
astigmatid mites
• Infestation, allergy, scrub typhus, rickettsialpox
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