this presentation gives you information about taxonomy and biology of medically important lice for humans

1. LICE
PRESENTED BY:
ANIL KUMAR(03)
MPHE Ist year
Vector Control Research Center
(ICMR)-2015-17
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2. INTRODUCTION :
• Worldwide more than 550 species of
louse have been reported.
• These are obligatory ectoparasites of
humans, cattles and animals.
• Lice are small, dorsoventrally flattened,
exopterygot wingless insects.
• Two different forms of lice have evolved :
- The Mallophaga
- The Anoplura
• The Mallophaga – they retains the
primitive insect mandibulate mouthparts
and feed on epidermal structures of birds
and mammals(chewing lice).
• The Anoplura – they evolve specialized
mouthparts for blood feeding and they
are only found on humans (host specific)
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MALLOPHAGA
Fig. 1. ANOPLURA

3. Contd. Introduction…
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• Three types of lice are there to be considered
under medical importance for humans based
on the part they feed on:
- Pediculus humanus capitis (head
louse),
- Pediculus humanus corporis (body
louse), and
- Pthirus pubis ("crab" louse/pubic
louse).
• Human lice survive by feeding on human
blood.
• Lice infestation are most commonly caused
by close person-to-person contact.
• Body louse is only reported to spread
diseases.
• Treatment is available, so identification can
help in taking accurate control measures.

4. Classification :
Phylum • Arthopoda
Class • Insecta
Order • Anoplura
Family
Genus
• Pediculidae
• Pediculidae humanus
• Phthirus
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6. Pediculus humanus
capitis
(Head louse)
 The adult lice are obligate blood sucking
ectoparasites that require warmth and a source of
human blood to survive.
 Reservoir : Human (susceptible- children)
 Transmission : person to person contact
 Oviposition site : Base of head hairs
 They will die if separated from human host for 24hrs
 Hemimetabolous (no pupa)
 No. of blood meals : 4 - 10/day
 Longevity of adults : Up to 35 days
 Reduced compound eyes no ocelli
 Crawling speed : 30 cm/min
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9. Eggs or Nits :
• Eggs are laid in their shells (the nits)
• Shape: oval or flask shaped and have a lid (operculum) that covers the free
end
• Colour: documented as grayish-white, transparent but turns to dark brown
after tanning
• Size: 0.3 mm – 0.8 mm
• After hatching, empty white to dull yellow and almost clear colored nit
casing or shells are left behind. They remain tightly adhered to hair shaft.
• Viable nits are always found close to the scalp (1 – 4 mm).
• Human hair grows slowly at an average rate of approximately 0.37 mm/ day.
Nits found several millimeters from the scalp are now empty egg cases.
• Egg is tightly glued to the base of the hair shaft, nearest the scalp with chitin.
• Eggs are usually deposited 1 – 4 mm from the scalp.
• Eggs hatch within 6 – 10 days.
• Only eggs deposited by inseminated female lice will hatch.
• May persist for months, even after treatment, if not removed.12/30/2015

10. • Looks like adult louse, but smaller and immature.
• Size: 1 mm in length, size of pinhead.
• Matures in 3 stages.
• They grow by molting or shedding their skin 3 times before reaching
adulthood.
• Duration of nymph stage is 7-14 days.
• Nymphs tend to remain on the head where they hatch.
• The newly hatched nymph will crawl and seek a place to feed
immediately.
• The three nymphal stages last about 8-12 days.
Nymph :
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11. Hy : hypopharynx Pm : prementum
Adult :
• Wingless, elongated body with 3 segments (head, thorax and abdomen).
• Short antennae with 4 segments.
• Small head with anterior piercing mouthparts that are used to pierce the scalp and
feed on blood.
• 6 short and stubby legs with single tarsal segments, with powerful hook-like claws at
the end of each leg. These claws are used to grasp the hair shaft.
• Dorsoventrally flattened.
• 3rd abdominal segment : As long as wide
• Female body length : 2.4 - 3.3 mm
• Male body length : 2.1 - 2.6 mm
• Mating only occurs once fully grown.
• Colour: have been documented as grey, tan, brown, red or black.
• Colour changes to rust coloured after a blood meal.
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12. Pediculus humanus humanus
(Body louse)
Head louse
Characteristics Head louse Body louse
Color Dark Light
Female body length 2.4 - 3.3 mm 2.4 - 3.6 mm
Male body length 2.1 – 2.6 mm 2.3 – 3.0 mm
Antennae shape Short and wide Long and narrow
3rd antennal segment As long as wide Slightly longer than wide
Abdominal indentations Prominent Not prominent
Apices of paratergal plates Extending into intersegmental
membranes
Didn’t extend to
intersegmental plates
Eggs laid 4 - 8 per day 8 - 12 per day
Oviposition site Base of head hairs Clothing fibers
Longivity 35 days 60 days
Blood meals 4 - 10 per day 1-5 per day
Body louse
Body louse differ from head louse with only few characters, namely
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13. • They can survive up to 1 week after getting separated from human host without
feeding
• Mouthparts same as head louse, piercing and sucking type
• The body louse is the vector of three bacterial diseases
- epidemic or louse-borne typhus, caused by Rickettsia
-trench fever, caused by Rochalimaea quintana (Rickettsia quintana)
-louse-borne relapsing fever, caused by Borrellia recurrentis (Lebert)
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14. Pthirus pubis
(Pubic louse)
• It is associated with poor hygiene condition or socioeconomic status
• Pubic lice are adapted to a sedentary life style on pubic hair, armpits,
sometimes on eyelashes/moustaches/beard and body hair.
• They are usually transmitted during sexual contact, and have been associated
with other sexually transmitted diseases.
• They do not cause any disease
• They look like crab in shape thus also known as crab lice which makes it easily
distinguishable from head and body lice
• Life cycle remains same in pubic lice i.e, Egg, Nymph and Adult only difference
seen is in duration of different stages during life cycle,
Stages Duration
Egg 6 - 8 days
Nymph (I) 5-6 days
Nymph (II) 9 – 10 days
Nymph (III) 13 – 17 days
Adult 15 – 25 days12/30/2015

15. The crab louse may be distinguished readily from the body louse or head louse by the
following:
• forelegs delicate, with long, slender claws;
• other legs very stout, with short, stout claws:
• thumb like process of tibia short and stout;
• abdomen very short and broad; segments 1-5 closely crowded, thus the stigmata of
segments 3-5 apparently lying in one lateral process.
• adult size 1.1 – 1.7 mm
• they can feed continuously for hours without retracting their mouthparts.
All legs of the body louse or head louse are stout; thumb like process of tibia very long and
slender, bearing strong spines, forelegs stouter than the others; abdomen elongate,
segments without lateral processes.
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16. Collection technique :
Mechanical method -
• Hand picking : Using a fine watch-repairer's forceps (BB or NN) one
can conveniently pick up the lice. Plucking the barbs of the feathers,
or hairs, holding a little below the louse will avoid crushing of the
specimen in the process.
• Brushing technique : The host should be separated and fumigants
(ether/chloroform/carbon disulphide) should be sprinkled over the
infested area in such a way that the fumigant should not come in
direct contact/affect the host. After 30 min comb the hair with fine
comb in such a way that all sample should fall on a white paper. The
specimens can be preserved in vials containing 70-95% alcohol.
Chemical method
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17. Preservation technique :
The specimen collected can be conveniently preserved in a liquid medium or
mounted on slides.
• Storing in liquid media : The material can be preserved in small glass vials
containing 70% - 95% alcohol, plugged with cotton or air tight plastic
stoppers (cork stoppers should not be used), while in case of specimens
which are placed in a large jar should contain 95% alcohol.
• Whole mounts
Resin mount : Elhel (1967) quoted Emerson's procedure of
mounting. In this process, after treating in KOH or NaOH solution, the
specimens were washed well with water (about 20 min.) and then placed in
40% alcohol (15 min.). They were then transferred to a solution of Ziehl
Nielson's Carbol-Fuchsin for about 30 minutes. The material then passed
through 70% alcohol (30 min.), 95% alcohol (15 min.) washed in absolute
alcohol, and then placed in Beechwood creosote (1 hr to overnight), and
finally mounted in Damar gum or Canada balsam.
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18. REFRENCES :
BOOKS:
• Proceeding of the workshop on techniques in parasitology, Zoological
Survey of India, Calcutta., 1980
• Michigan head lice manual, Michigan department of education.,
August 2013
JOURNALS :
Amina Boutellis, Laurent Abi Rached, Didier Raoult., The origin and distribution
of human lice in the world., Infection, Genetics and Evolution 23(2014);
page 209-217
Denise L. Bonilla and et al., The Biology and Taxonomy of Head and Body Lice –
Implication for Louse-Borne Disease Prevention., PLOS Pathogen 9;
November 2013
Elston DM., What’s Eating You? Pediculus humanus (Head Louse and Body
Louse). CUTIS. Vol. 63, May 1999; p. 259
H. V. Weems, Jr. and T. R. Fasulo., Crab Louse, Pthirus pubis (Linnaeus) (Insecta:
Phthiraptera (Anoplura): Pediculidae)., University of Florida, EENY-103
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19. THANK
YOU
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