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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. Ticks and Mites (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)
Ticks (3 families):
Prostigmatid and Astigmatid Mites
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.Cladistics16, 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.
Female hard tick
GenusApprox. # SpeciesDistribution
Amblyomma 100 7 worldwide, mostly tropical
Dermacentor 31 7 worldwide
Hyalomma 30 0 Africa, Asia
Nosomma 1 0 India, SE Asia
Rhipicephalus 68 3 Ethiopian / tropicopolitan
Haemaphysalis 155 2 worldwide
Ixodes 217 40 worldwide
Margaropus 2 0 southern, east Africa
Bothriocroton 5 0 Austrailia
Genus Haemaphysalis: Small, both sexes similar, important in enzootic cycles
Genus Rhipicephalus: African origin, but several species worldwide in the tropics (now includes previous species of Boophilus, non-ornamented, one-host ticks)
GenusApprox. # speciesDistribution
Otobius3 western hemisphere
a. observation on hosts and premises
c. CO2 - baited traps
a. Natural predators
b. Repellents/toxicants for human use
I. DEET (apply to skin)
II. Pyrethroids (apply to clothing)
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.
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.
Removal of an embedded tick using fine-tipped tweezers.
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.
Haemaphysalis bremnerimouthparts, showing toothed, sawlike hypostome.
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
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, Neorickettsia, and Wolbachia.
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 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.
E. chaffeensis transmission (HME)
Average annual incidence of reported human monocytic ehrlichiosis (HME) by county, using 1995 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, and wild rodents are likely reservoirs.
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
Average annual incidence of reported human granulocytic ehrlichiosis (HGE) by county, using 1995 population census data.
Distribution of the Tick Vectors of Ehrlichia and Anaplasma in the United States
female, male, nymph, larva
White-tailed deer important vertebrate host of adult ticks
Month of Lyme disease onset for reported cases, United States - 1992-1998.
erethyma chronicum migrans
(bull’s eye rash)
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
Characteristic spotted rash of late-stage Rocky Mountain spotted fever on legs of a patient, ca. 1946
Rocky Mountain wood tick
American dog tick
the United States, 1942-1996.
Mountain spotted fever, 1993-1996.
spotted fever by state and region, 1994-1998.
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
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
(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
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
(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
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
Usually less than 1 mm long, life cycle: egg-larva-nymph-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
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. dermatitis or other tissue damage
2. loss of blood or other tissue fluids
3. transfer of pathogenic agents
4. cause of strong allergic reactions
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.)
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)
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.)
1. Removal from outside host, with wash
2. Skin scraping for intradermal forms
3. Drag similar to tick flagging
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
Rickettsia akariLiponyssoides mite vector
House mice, rats - vertebrate hosts in urban areas
Larval chigger mite
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