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.
👉 Chennai Sexy Aunty’s WhatsApp Number 👉📞 7427069034 👉📞 Just📲 Call Ruhi Colle...
Entomology Louse, Bedbugs & Sand fly
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
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
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.
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
Editor's Notes
For example,
in humans, different species of louse inhabit the scalp and pubic hair
Head lice found anywhere on the head (typically hair, but also can be found on the eyebrows.)
Body lice: typically found on the clothing, except when they need a blood meal. They then move to the skin (but usu found on the clothing NOT the skin)
Pubic lice: usu found in pubic hair but are adapted to any other type of coarse hair (armpit region etc.)
All of the lice types are six-legged
Differ on the basis of morphology (see pictures, especially pubic lice), where they can be found as discussed above, and size
Photo Credit: CDC http://www.cdc.gov/parasites/lice/index.html
Genetic analysis has shown that a single pregnant bed bug, possibly a single survivor of eradication, can be responsible for an entire infestation over a matter of weeks, rapidly producing generations of offspring.
Some species are selective, whereas others bite any suitable host they find.