Ticks and mites

Chiggers
Harvest mites
Kedany
Scrub mite

The vector mites belong to the order Acarina
and family Trombiculidae which comprises
many hundreds of species of world wide
distribution
They are found in great abundance in areas with hot, humid
climate, thick vegetation and presence of small vertebrates
like rodents. The foothills in subtropical and temperate regions
offer them ideal conditions.
Exercise
Mites are more prevalent in regions with perennial weather
True
False

Exercise
Which of the following is also called as
“Chigger”
A. Tromboculid Mites
B. Sarcoptes Scabies
C. Anopheles
D. Aedes Aegypti
Tromboculid Mites

Morphology
 Adult is about 3-4mm in size
 Densely covered with hair and has a figure of eight
 Mouth parts consist of a pair of chelicerae and a pair of
palps.
 Adult resembles the nymph except that it is larger and
more densely covered with hairs.
 Larva is pale yellow to orange-red in colour with…
 Circular body bearing
 Three pairs of legs and
 Branched hairs on the body and on the legs.

Exercise
Which is the parasitic stage in mites
Egg
Larva
Nymph
Adult
All of the above
Larva

Life Cycle
 Takes 6 to 12 weeks for its development from egg to adult
 The stages in the life history of a mite are egg, larva, nymph and adult.
 The eggs laid singly on the surface of the soil.
 Larva leaves the egg-shell and becomes very active….
…moving quickly, it seeks a suitable host such as rat, mouse etc.
 Larva feeds on the lymph and the tissue fluid but not on blood of the host.
 Larvae feed for 2 to 3 days and then drop off to the ground concealing themselves
in loose soil, and here they develop into nymphs and finally into adults.
Only the larval stages are parasitic; the nymphs and adults are never parasitic and
feed on small insects in the soil or their eggs

Exercise
The orange red colour of the tromboculid
larva mite is due to ingested blood.
True
False
False

Bionomics
 Distributed in areas ideal for their survival called as “Mite Islands”.
 Mite Islands are patches of ground characterized by
 Thick vegetation cover, mainly the scrub jungles or other tall grasses
offering protection from direct sunrays and desiccation
 Nearly 100% relative humidity at ground level
 Ideal ambient temperature of 27± 5°C.
 Shelters animals like rats, mice etc. are also the reservoirs of
rickettsiae for which the trombiculid mites are vectors.
 Mites are most active during the whole rainy season
 In dry season, the adults migrate deeper into the soil, the egg laying
ceases and the mite islands shrink

Exercise
• Which of the following transmits scrub typhus
Mites
Tick
Flea
louse
Mites

Diseases caused by mites
Disease Vector Causal organism Reservoir
Scrub typhus L. deliense Orientia tsutsugamushi Rodents
Rickettsial pox Allodermanyssus sanguineus R akari Rodents
Scabies S scabei Man

Vector Potential
 In India, Leptotrombidium deliense is the vector of Orientia
tsutsugamushi causing Scrub typhus
 Rickettsiae taken up by larvae while feeding on rodents are carried
through its nymph, adult stages and then its eggs (trans-stadial
transmission).
 The larvae hatching out of these infected eggs are capable of
transmitting the rickettsiae to the next host.
 The infection is thus trans-ovarially transmitted for some generations
and hence the mite also acts as a reservoir of infection.
 Larvae feed only once during their life time causing transmission of
infection occuring in second or subsequent generations.
 Larva comeing in contact with a human being feeds on lymph;
rickettsiae contained in the mouth parts are injected into the lymph
of the human being thereby causing scrub typhus.

Itch Mite (Sarcoptes Scabiei)
 Found all over the world.
 Infestation is more common when living is congested.
 All stages (egg, larva, nymph and adult) are completed in the skin, the
development from egg to the adult occurring in about two weeks.
 The female makes zig-zag burrows and lays eggs deep in the horny layers
of the skin.
 Eggs develop into three legged larvae, which enter hair follicles and grow
into nymphs and adult.
 The adult is 0.4 mm in length and oval in shape with flat ventral and
convex dorsal surface.
 The spines and bristles on its body given it the appearance of a hedgehog.

Continue….
 The male dies after mating, leaving behind the fertilized female to cause
the disease.
 Interdigital webs, wrists, elbows, feet, penis, scrotum, buttocks and
armpits. Face, palms and soles are always free in adults but may be
involved in children: Predilection
 After a month or 2, erythematous patches are seen around the burrows
which develop into papules and vesicles.
 Itching is intense at night, which leads to scratching and secondary
infection.
 Personal contact of prolonged nature, such as sharing the same bed, is
needed for infection.
 Transmission through bedlinen is not likely as mites prefer the warm body.

Prevention and Control
 Direct contact with the infested person, or indirect through
undergarments, should be avoided.
 Proper personal hygiene should be observed including bath with soap and
water
 The infested persons and contacts should be treated thoroughly with 3 to
5% percent sulfur ointment or 20 to 25 percent benzyl benzoate
emulsion.
 The old clothes should be sterilised by boiling.
 Second application may be necessary.
 Tetmosol 5 to 10%in soap is a good prophylactic; apply three times a day.
 0.5 to 1 percent BHC or Gamma HCH (lindane) in coconut oil applied on
the affected parrts 2-3 times at interval of 2-3days.

Morphology
 Distinguished from other acarines by their relatively large size and
absence of prominent hairs on the body.
 Oval in shape and of varying colours and dorsoventrally compressed.
 Females are larger and are capable of great distention.
 Both sexes and all other stages thrive on blood alone
 They are free living on the ground in between various moults during
development.
 Two families, Family Ixodidae which is the HARD TICK and Family
Argasidae which is the SOFT TICK.
 The hard tick is more a jungle tick while the soft tick is a domestic or
household tick like a bedbug.

Exercise
Which is the parasitic stage in Ticks
Larva
Nymph
Adult
All of the above
All of the above

Hard Ticks
 Dorsum of the adult male is covered by a dark shield, called
scutum.
 This may be ornate with grey or white ‘patterns’.
 In females and immature males, it covers only the anterior part
 ‘Capitulum’ is the false head, actually formed by the mouthparts
anteriorly
Soft Ticks
Oval with leathery cuticle and devoid of scutum.
Mouth parts are placed ventrally and hence not visible from above

Exercise
False about ticks
A. Cant stand starvation
B. Has a very short life span and always found on
host
C. Scutum is present in the entire back of male and
in a proportion in females
D. Readily comes out in night for feeding
Cant stand starvation

Life Cycle
 Passes through stages egg, larva, nymph and adult taking 6 weeks to 2
years
 Fertilized female (Fed) drops off to the ground and lays eggs in cracks and
crevices.
 Hard ticks deposit all their eggs in a single act of oviposition after which
they die.
 Eggs take a few weeks to several months to hatch.
 Larvae are six legged and do not feed for about a week after emergence
does QUESTING after this period
 Nymphs emerge after 1st moulding with 4th pair of legs and does
Questing, feeds and again drop off.
 They again moults to adulthood and become sexually mature being
parasitic and exhibiting questing
 Copulation takes place after the last moult and the male dies after
fertilizing the female.

Exercise
Which of these regarding ticks is not true
A. Females are larger than males
B. Both sexes thrive on blood alone
C. They are free living on the ground in between
various moults
D. All are true
All are true

Bionomics
 Hard ticks are open jungle dwellers and thrive on animal hosts
 Do not attach themselves to human beings voluntarily but
accidentally.
 Soft tickson although preferentially parasitic on animals and birds
attack man voluntarily.
 Found in human dwellings and cattle sheds and attack man and
animals during their sleep.
 They however, live away from their hosts, in cracks and crevices
and only emerge at night to feed on the host.
 Ticks can survive starvation for a long time

Hard and Soft ticks
Attributes Hard Tick Soft Tick
Life Cycle O->L->N->A O->L->N1->N2->N3->…A
Habitat Free range species; attacks host
in the day
Burrow inhabiting species ;
basically a nocturnal feeder
Nymph 1 instar Several (5-7) instars
Adult Feeding 1 blood meal Intermittent feeders (5-12 or more)
Hosts 1-3 hosts More than 10 hosts
Egg laying Tjhousands in a single batch Less than thousand in several
batches
Life span 2 months – 3 years Long duration ( as long as 16
years)

Diseases caused by Ticks
Disease Vector Causal organism Reservoir
Kyasanur Forest
Disease (KFD)
Hard ticks species Arbovirus group B Monkeys/Birds
Tick typhus Hard ticks species R conorii Dogs
Tularaemia Hard ticks species P tularensis Rabbits/
Rodents/cattle
Relapsing fever Soft Tick B duttoni Rats

Exercise
All of the diseases are caused by ticks
except
A. Relapsing fever
B. Tularemia
C. Epidemic typhus
D. Tick typhus
Epidemic typhus

Vector Potential
 Diseases in man by transmitting the viruses, rickettsiae,
spirochaetes and bacilli of infectious diseases and through toxin
present in their saliva.
 Factors which account for high vector potential are that
 All the stages are haematophagous and are
 Persistent blood suckers
 While feeding they attach firmly and cannot be easily removed.
 They are resistant to varying environmental conditions and relatively
protected from natural enemies.
 Trans-stadial and transovarian transmission of infection helps in
maintaining infection for several years.
 Power to regenerate lost parts such as amputated legs and also the
ability to repair mutilated mouth parts, which conserves them for
long.

Control of Ticks and Mites
A. Area Treatment :
 “Malathion 50% EC” (as 5% solution) / “Cyfluthrin EC” should be sprayed
B. On Vegetation
 Spraying Malathion, Fenthion, Propoxur and Permethrin are suitable
C. Domestic Animals :
 Wash or spray containing 2% Malathion, 1% Propoxur, Deltamethrin (0.025%)
 Personal protection using Dibutyl-phthlate (DBP), Diethyl phenyl acetamide (DEPA)
and Diethyltoluamide (DEET).
 Wearing body covering clothing
 Walking while on grass
 Use of Insecticide treated mosquito net
 Removal of shrubs, trees, or tall grass can be useful in recreational areas.
Insecticidal Control
Habitat Management
Personal Protection
Anti-Rodent Measures

Ticks and mites

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