Medical entomology

1. Insects of Public Health
Importance

2. 1. Mosquitoes
Anophilines, Culicines
1. Flies
House fly, sand fly, Tsetse fly, black fly
3. Human lice
Head
and body
lice, crab
lice
4. Fleas
Rat

3. Flies

4. Insecta or hexapoda
• 6-7 cm long, hairy
• Three body segments
• Six legs
• Two pairs of wings
• Wings-transparent, no
veins

5. House fly
•A pair of
compound eyes
•Eyes are closer in
males and far apart
in females
•Antenna - small &
3 segmented

6. House fly- life
cycle
• Egg- 150-200eggs/sitting
1mmlong, pearly white
2 longitudinal ridges in dorsal side
• Larva (maggots) – white segmented(13)
footles, worm like,1/2 inch. narrow anterior end &
broad posteriror end
no eyes / appendages

7. Contd…
• Pupa- white in early stages, later it
become dark brown. Barrel shaped

8. •2-6 d
•2-7 d
8-24hr

10. Mechanical transmission of diseases
• Viruses : Hepatitis, poliomyelitis.
• Bacterial : Enteric fever, bacillary
dysentery, wound infection & trachoma.
• Parasitic :
Eggs:
Mechanical transmission of
Ascaris ,Trichuris,
Hymenolpis nana…
Cysts: Entameba histolytica, Giardia

11. Fly control
1. Environmentalcontrol
clean house with clean surroundings
1. Insecticidalcontrol
DDT (5%), lindane(0.5%), fenthion (2.5%),
malathion(5%), diazinon (1-2%) etc as
residual/space spray/Baits
1. Fly papers –resin & castor oil
2. Protection against flies-screening (14mesh/ in)
3. Health education

12. Sand fly

13. Phlebotominae
• Like a mosquito, except
its body is hairy and the
wings are feathery.
• Tiny insects (1-3 mm)
• Smaller than mosquitoes
• Hairs on body and wings
• Wings rest over body like
“angel’s” wings
• Only females suck blood

14. Sand flies Phlebotomus spp
• Live in warm climates
• Minute, hairy ,with wing kept erect while
resting.
• Breed in crack of soil and wall, rubbish
heaps
• Move in hops rather than fly .
• Nocturnal ,during day time rest in cool damp
places
• Vector of leishmaniasis, sand fly fever.

15. Sand fly
• Large compound eyes
• Hairy legs
• Long slender legs
• Wings are vertical and pointed
• Whole body is covered with hairs
• All 10 segments are abdomen are visible

16. Sandfly
• In males 2 claspers
are seen in the 10th
abdominal segment
• In females ,10th
abdominal segment
has 2 small cerci

17. Sand fly
Vector for Leishmaniasis
◈L.Donovani -visceral leishmaniasis.
◈L. tropica -cutaneous leishmaniasis.
◈L.braziliensis -mucocutenous.
Transmission cyclopropagative.
◈Sand fly fever viral disease
mild fever like influenza
propagative

18. Fleas of medical importance

19. Ctenocephalides
• Ecto- parasites of dog and cat
• Characterized by black teeth like structure
on head known genetal comb and
another set on first thoracic segment-
pronotal comb

20. Dog flea, cat flea
Human flea Trop. rat flea
dog flea cat flea

21. Ctenocephalides canis
Rat flea
Pulex irritance

22. X. cheopes • Main vector for plague
• Females have “C”shaped
spermatheca with uniform
thickness which is used for
storing sperms
• In males spermatheca is
absent, the 9thabdominal
segment dorsally has a
sensory organ-pygedium
• Anterior to this is anti
pygedial bristles arise
directly from the body
• 9th sternite is club
shaped

24. X. astia
• In female-spermatheca is bulbus at the
middle –a shaped
• In male- anti pygedial bristles
arise directly from the body
• 9th sternite is ribbon shaped

25. X. braziliensis
• In female-spermatheca is bulbus at one
end –b shaped
• In male- anti pygedial bristles
arise from a conical base
• 9th sternite is absent

26. Fleas transmited
• Plague (bubonic)
• Endemic or murine typhus
• Chiggerosis
• Hymenolepis diminuta
• Modeof transmission
◈Biting-blocked flea
◈Mechanical transmission
◈Faecal

27. Control of fleas
• Insecticides
◈DDT(5-10%),γHCH, dieldrin, diazinon(2%)
◈Applied in floors & walls up to 1ft
◈Applied in rat burrows
• Repellents
◈Diethyl toluamide
• Rodent control

28. Human lice

29. Lice
• Small wingless insects
• Three species that solely live on humans
◈Pediculus humanus occurs in two subspecies
the head louse ( Pediculus capitis) and
the body louse ( Pediculuscorporis)
• The body louse lives mostly in the
clothing and attaches its eggs to its
fibers
• The third species of human lice is
Phthirus pubis the crab or pubic louse.

30. Head louse- Pediculus humanuscapitis
• The head louse lives in the hair and
attaches eggs (nits) to the hair
• Body - dorso-ventrally flattened, has head,
thorax & abdomen
• Head-pointed, bears a pair of 5 segmented
antennae, Simple eyes.Head has a pair of
antennae which is sucking & piercing type
• Thorax(square shaped) has 3 pairs of
appendages.Last segment of appendages
ends with claws
• Abdomen – 9 sements.Last segment imale it
is pointed, females - bilobed

31. Head louse
•In females last
abdominal segment is
bifid
•In males last
abdominal segment is
pointed not bifid.
•Males posses a U
shaped organ called
”aedeagus
•Aedeagus is species
specific and region
specific

32. Pubic Louse
Pthirus pubis - • Resembles a crab, about 2mm
• Attached to pubic hair & eye
lashes
• Head, thorax, abdomen
• Thorax has 3 pairs of legs & first
pair is slender
• Last segment of appendages ends
with claws
• Abdomen has lateral projections
called lateral papillae
• Females last abd.segment is bifid
• In males last segment is not bifid.

33. Lice -PH importance
disease transmission:
lice act as a vector for
- Epidemic typhus
- Epidemic relapsing fever,
- Trench fever.
Pediculosis, irritation and
pruritus.

34. Control of lice
• Insecticide s -Lotion with 0.5%
malathion,toapplied and kept on for 24-48 hrs.
• Personal hygiene

35. Ticks
• Wingless insects
• Ectoparasites of vertebrate animals
• They all suck blood
• Body is oval in shape ,and has two parts- head or
Capitulum & Abdomen
• Head is at anterior end
• Has 4 pairs of appendages, no antennae
• Hard tisks are covered on their dorsal
surface by a chitinous schield called scutum

36. Hard ticks • Males are smaller than
females
• In males body is
completely covered by
scutum
• In females anterior 1/3rd
is covered by scutum
• Vertical transmission
from mother to egg

37. Hard tick
Male
Female

38. Hard tick
Female
Male

39. Soft tick •Small, soft and leathery cuticula,
•Mouthparts invisible from dorsal
aspect
•The scutum/ dorsal schield is
`absent
• Abdominal wall is
smooth
• Dorsal surface has
small dot like
mamillary
tubrercles

40. Soft and hard ticks
(Agasidae/Ixodidae)

42. •Hard tick hard cuticle
- Babesiosis,Tularemia
- Quneensland fever,
- Rocky mountain spotted fever,
- Tick paralysis ,KFD
•Soft tick soft cuticle
- Relapsing fever Borrelia duttoni
- Q fever
- KFD

43. Mites – sarcoptes scabei
• Tiny (0.1- 0.3 mm) endo-parasitic
mite
• Lives in epidermal layer of skin
• Body - Capitulum & Abdomen
• Eyes, antennae & wings are
absent
• 2 pairs of legs in front 2 pairs
behind. Front legs end in long
tubular process- suckers
• Hind legs end in long filamentous
bristles
• In females 4 thpair end in suckers

44. sarcoptes scabei
Female
Male

45. sarcoptes scabei- Public health imp
• Causes human scabies
• Scabies is characterized by an intensely
pruritic, erythematous, papular eruption
caused by burrowing of adult female mites
in upper layers of the epidermis, creating
serpiginous burrows. Itching is most
intense at night
• Sites of lesion – hands & wrist
(63%),extensor aspect of wrist (11%),

46. ▶Preferred sites interdegital, popliteal fold and groin

47. Cyclops • Class-crustacea
• Pear shaped semi
transparent body, forked
tail, 2pairs of antennae
• Large cephalothorax &
slender segmented
abdomen
• Single small pigmented
eye
• In females 1stabd. segment
has apair of ovisac

48. Cyclops
Female
Male

49. Cyclops (water flea)
• Vector for:
Dracunculus medinensis

50. Control
• Physical
straining of water through a piece fine cloth
Boiling at 60 degree C
• Chemical – chlorine 5ppm,alum
4gm/gallon, abate 1mg/l
• Biological – gambusia fish
• Abolish step well, promote sanitary well