Body lice are the most serious human lice because they can transmit diseases like epidemic typhus. Diseases spread by body lice are severe threats, especially to refugees and those affected by humanitarian crises. Controlling body lice requires insecticide spraying of clothing and living areas, in addition to personal hygiene measures.

1. Entomology
Part-IV
By
Dr Utpal Sharma
Assistant Professor
Department of Community Medicine
SMIMS, Gangtok, Sikkim

2. Louse (plural: lice)
 Common name for members of over 3,000 species of wingless
insects of the order Phthiraptera
 Taxonomic classification
 Phylum:Arthropoda
 Class:Insecta
 Subclass:Pterygota
 Order:Phthiraptera
 Three of which are classified as human disease agents.
 Head louse (Pediculus humanus capitis)
 Body louse(Pediculus humanus humanus/corporis)
 Pubic louse(Pthirus pubis)
 They are obligate ectoparasites of every avian and mammalian
order except for monotremes (the platypus and echidnas), bats,
whales, dolphins, porpoises and pangolins.

3. Biology
 Color varies from pale beige to dark gray; however, if feeding on
blood, it may become considerably darker.
 Female lice are usually more common than the males, and some
species are even known to be parthenogenetic.
 A louse’s egg is commonly called a nit.
 Many lice attach their eggs to their host’s hair with specialized
saliva; the saliva/hair bond is very difficult to sever without
specialized products.
 Lice inhabiting birds, however, may simply leave their eggs in
parts of the body inaccessible to preening, such as the interior of
feather shafts.
 Living lice eggs tend to be pale white. Dead lice eggs are more
yellow.

4. Cont….
 Most lice are scavengers, feeding on skin and other
debris found on the host’s body, but some species feed
on sebaceous secretions and blood.
 Most are found on only specific types of animals, and, in
some cases, on only a particular part of the body;
 Some animals are known to host up to fifteen different
species, although one to three is typical for mammals,
and two to six for birds.
 Lice generally cannot survive for long if removed from
their host

5. Vector Biology
Three types of lice:
Head lice: Pediculus
humanus capitis (2-3 mm long)
Body lice: Pediculus
humanus humanus (2.3-3.6
mm long)
Pubic lice (crabs): Phthirus
pubis (1.1-1.8 mm long)

6. Morphology of louse
 Dorsoventrally flattened, elongated body is divuded into head,
thorax and abdomen
Head
 Smaller than thorax, rectangular-ovoidal and pointed
anteriorly
 Antennae 5 jointed pair situated anterior to eye
 Bears 6 pairs of prestomal teeth haustellum.
 Teeth used to anchor to the skin and everted during sucking.
 Cutting organ/stylet contains..
– A pair of fused maxillae
– Hypophyrynx
– Labium placed ventrally supporting hyphyrynx and maxillae

7. Morphology of louse

8. Cont…
Thorax
 Squarish in shape
 Externally 3 segments not distinct
 Possess 3 pair of very strong legs,each of the leg 5-
segmented
 Tarus is unjointed each ends in a hooked claw
 A thumb like projectio lower part of each tibia helps insect to
grasp hair /fibre with tarsal claw
Abdomen
 Divided into 9 segments
 Posterior part narrow and rounded in males
 In females terminal segment is bilobed
 Last segment bears a pair of internally curve gonopods
used to grasp hair or fibre

9. Life cycle
 Three stages in the life cycle of a louse
 Eggs
 Called “nits”, laid singly or in groups, are firmly attached to the hair or
fibreby cementing substance
 Small white ovoid bodies, pointed at one end and truncated and pitted at
one end.
 Female lays upto 300 eggs at the rate of 4-9/day
 Hatches within 6-9 days under favourable conditions (>22° C)
 Larva/ nymph
 Looks very much like the adult
 Feeds on host acquires maturity after 3 moulds
 Stage may take 10 -15 days
 Adults
 Entire cycle takes around 15-17 days from egg to adult
 Adult lives around 30-50 days

10. Life cycle of louse

11. Public health importance
Lice are the vector of the following
diseases:
Disease Causative agent
Epidemic typhus Rickettsia prowazeki
Relapsing fever Borrelia recurrentis
Trench fever Rickettsia quintana
Dermatitis Due to scratching and secondary
infection

12. Control of lice
Insecticides
 Head & crab lice
 Lotion containing 0.5% malathion
 Should be left for 12-24 hours and than washed
 Dust containing carbaryl is also effective
 Body lice
 Powder containing 1% of malatthion is treatment of choice
 Applied to the inner surface of the clothing and socks
 About 50 gm of insecticidal powder id needed for single person
 Personal hygine
 Daily bath with soap and water
 Good care of long hair
 Clothings tobe washed in hotwater and soap and ironed

13. Summary
 Body lice are more serious than pubic or head lice
because they can transmit disease.
 Diseases associated with body lice are severe!
Epidemic typhus (R. prowazekii)
 Refugees and those affected by humanitarian crises are
particularly at risk.
 Insecticide spraying is an important control measure

14. Bed bugs
 The name “bed bug” derives from the preferred habitat of the
insect: warm houses and nearby or inside of beds and beddings.
 Parasitic insects that feed exclusively on blood.
 Feeds on their hosts without being noticed.
 Taxonomic classification
 Phylum:Arthropoda
 Class:Insecta
 Order:Hemiptera
 Suborder:Heteroptera
 Family:Cimicidae
 Family Cimidae consists of 4 subfamilies and 35 species, of these
only C. Lectularis and C hemipterus are medically important.
 Cimex lectularius, the common bed bug, is the best known, as
it prefers to feed on human blood.

15. Biology
 Adult bed bugs are light brown to reddish-brown, flattened, oval-shaped
and have no hind wings.
 Newly hatched nymphs are translucent, lighter in color and become
browner as they moult and reach maturity.
 Adults grow to 4–5 millimetres long and 1.5–3 millimetres width.
 Nymph of any age, has just consumed a blood meal have bright red
translucent abdomen.
 In next several hours fading to brown and to opaque black within two
days as the insect digests its meal.
 Bed bugs, when warm and active their movements are more ant-like.
 Like most other true bugs, they emit a characteristic disagreeable
odor when crushed due to their stink gland in the metasternum

16. Morphology
Dorso-ventrally flattened,measures 4-6 mm in length and 3
mm in breadth
Body consists of head, thorax and abdomen
Head
 Short and broad with two small compound eyes
 4 jointed antennae, long and slender
 3 jointed proscis , it is kept withdrawn on the ventral surface of
the head and thorax when not sucking blood
Thorax
 Consists of 3 segments,prothorax is the largest one.
 Has 2 wing like expansions anteriorly
 The front wings are vestigial and reduced to pad-like
structures, covers the 2nd & 3rd segments
 The tarus is 3 segmented , ends in 2 small claws

17. Morphology cont…
 Abdomen
 Has 9 segments
 Tip of the abdomen is broad in females and narrow in males.
 Males has reproductive organs on the 8th segment whereas a slit
acts the same on th 4th segments in case of females
 Bed bugs have segmented abdomens with microscopic
hairs that give them a banded appearance.

18. Life cycle
Bed bugs are hemimetabolous, consisting of egg, 5
immature nymphyl stages and a final sexually mature
adult stage.
Each nymphal stage requires about 5-7 days
Whole life cycle completed in as little as one to two
months
Both male and females sucks blood, the nymphs and
adult takes blood intermittantly.
In a single blood meal it may take 7.6 gm of blood
A female with enough food can lay lay three to four
eggs each day continually 200-500 eggs in a lifetime

19. Life cycle cont….
Eggs are white, flask shaped about 1mm long and
sticky,seen in cluster.
Laid in the cracks and crevices along with the black
tarry stool
Adult can live for 1-1.5 years, with frequent feeding
and lives only 3 months without food
They attack man once or twice a week usually during
night
Bed bugs can detect prey only upto a distance of 10
cm.
 in dark sorroundings and starved conditions they also
bite in the daytime.

20. Life cycle of bed bug

21. Public health importance
Bed bugs can cause a number of health effects,
including skin rashes, psychological effects, and
allergic symptoms.
Can be infected by at least 28 human pathogens,
but no estabilished evidence of transmission of
the pathogen to a human being with possible
exception of Hepatitis B.
Experimentally transmitter of kala-azar, oriental
sore, leprosy Chaga’s Disease, typhus etc.
Bed bug bites or cimicosis may lead to a range of
skin manifestations from no visible effects to
prominent blisters.

22. Cont…
Diagnosis involves both finding bed bugs and
the occurrence of compatible symptoms
Treatment involves the elimination of the
insect and measures to help with the
symptoms until they resolve.
They have been found with methicillin-resistant
Staphylococcus aureus (MRSA) and
with vancomycin-resistant Enterococcus

23. Control of bed bugs
 Control is very difficult, resistant to DDT, BHC, and Deldrien
 However following measures to be adopted:
 Search to know the extent and location of the infestation
 Use of soap and warm water to clean the infested articles
 Insecticides- Pyrethrum sprays (0.2%),addition of pyrithrin (0.1-
0.2%) in insecticidal formulation increases efficacy
 Other insecticides- Malathion (-2%), Prorpoxur (1%) and
Dichlorovs(0.5%)
 Dose-Approx. 1 lit/25-5-m2
Precautions
 Complete air dryiny of beddings before reuse
 Infant bedding including cradels not to be treated with
insecticides

24. Sandflies
 Sandfly is name for any species or genus of flying, biting, blood
sucking Dipteran encountered in sandy areas.
 Taxonomic classification
 Phylum:Arthropoda
 Class:Insecta
 Order:Diptera
 Family:Psychodidae
 Subfamily:Phlebotominae
 Phlebotominae subfamily contains more than 600 species.
 Important of these are P. argetipes, P. papatasii, P. sergenti
and S. punjabensis

25. Biology
 Small insects, light-brown in colour.
 Measures 1.5-2.5 mm in length with their wings and bodies
densely clothed with hair.
 About 30 species recorded in India
 Only females, sucks blood (0.1-0.25 ml) for oviposition.
 In feeding on blood, they use their mouthparts to bleed the host,
then suck up the exposed blood.
 Inject biochemicals inhibiting blood clotting and…..
……… stimulates mast cells to produce histamine
distending capillary vessels, promoting blood flow
 Cannot fly more than 1Km from its breeding place.

26. Morphology
 Body divided into head, thorax and abdomen
Head
 Bears a pairs of long, slender and hairy antennae,palpi and
proboscis.
Thorax
 Bears a pair of wings and 3 pairs of legs.
 Wings upright,lanceolate and densly hairy and devoid of scales.
 Legs, longer than the body and slender
Abdomen
 Has 10 segments and covered with hair.
 Males has 3 claspers attached to the posterior end of the
abdomen.

27. Morphology
Pair of wings (Hairy)
Head
Thorax
Abdomen
Antennae
Legs (longer than the body) Proboscis

28. Life cycle (stages)
 Female lays eggs in batches of 40-50.
 Eggs are laid in dark humid animal burrows, cracks
or crevices, or under dead leaves
 Eggs torpedo shaped, hatch within 3-7 days
 Larva is apodous maggot, with distinct head, 3
thoracic and 10 abdominal segments, eyes absent
 There are 4 larval instars, the larval stage lasting a
total of 4-6 weeks
 The pupa requires 10-15 days for development
 Usually lives for 15 days, total life span is about 40
days

29. Life cycle of sandfly
Adult
Egg
Larva Instar I
Larva Instar IV
Larva Instar III
Larva Instar II
Pupa

30. Sand fly vs. mosquitoes
Size- smaller than the mosquitoes
Wings- upright,lanceolate in shape and devoid of
scales.
Legs- longer than the body
Hairs- Sandfly is a hairy insect
Hopping- Generally hops and do not fly by choice
If they flies, usually don’t fly above 3 feet.

31. Habits
Mostly found in cowsheds and mudhuts
Distributed throughout the seasons, peak density
in July to November.
They are troublesome nocturnal pests
Bite is irritating and painful, while their presence is
hardly observed.
Infests dwellings during the night and takes shelter
in holes, crevices, stables and dark corners.
Females requires bloodmeal every 3rd or 4th day for
oviposition.

32. Public health importance
Sandflies are the vectors of many
diseases of public health importance
Diseases transmitted
Species Diseases carried
Phlebotomus argetipes Kala-azar
Phlebotomus papatasii Sandfly fever
Oriental sore
Phlebotomus sergenti Oriental sore
Sergentomyia punjabensis Sandfly fever

33. Control of sandflies
 Control is easy owing to lesser ambulation of the insect
Insecticides
 Still sensitive to DDT, a dose of 1-2 gm/m2 or 0.25gm/m2 of
Lindane
 DDT effective for 1-2 years while for lindane it is 3 months
 Spraying should be done in human dwellings, cattle sheds and
other places
Sanitation
 Removal of shrubs and vegetation within 50 yards of dwellings
 Filling up of the craks and crevices
 Locating cattleshed at a fair distance from human habitation