insects of public health importance
DESCRIPTION
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Insects of Public Health Importance
1.MosquitoesAnophilines, Culicines
2.Flies House fly, sand fly, Tsetse fly, black fly
3. Human liceHead and body lice, crab lice
4. FleasRat fleas, sand fleas
5. Reduvid bugs
Flies
Insecta or hexapoda
• 6-7 cm long, hairy
• Three body segments
• Six legs
• Two pairs of wings
• Wings-transparent, no veins
House fly
• A pair of compound eyes
•Eyes are closer in males and far apart in females
•Antenna - small & 3 segmented
House fly- life cycle
• Egg- 150-200eggs/sitting1mmlong, 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
Contd…
• Pupa- white in early stages, later it become dark brown. Barrel shaped
•2-7 d
•2-6 d
8-24hr
Mechanical transmission of diseases
•Viruses : Hepatitis, poliomyelitis.•Bacterial : Enteric fever, bacillary
dysentery, wound infection & trachoma.
•Parasitic : Mechanical transmission of Eggs: Ascaris ,Trichuris, Hymenolpis nana… Cysts: Entameba histolytica, Giardia
Fly control
1. Environmental controlclean house with clean surroundings
2. Insecticidal controlDDT (5%), lindane(0.5%), fenthion (2.5%), malathion(5%), diazinon (1-2%) etc as residual/space spray/Baits
3. Fly papers –resin & castor oil4. Protection against flies-screening
(14mesh/ in)
5. Health education
Sand fly
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
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.
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
Sandfly
• In males 2 claspers are seen in the 10th abdominal segment
• In females ,10th abdominal segment has 2 small cerci
Sand fly
Vector for LeishmaniasisL.Donovani -visceral leishmaniasis.L. tropica -cutaneous leishmaniasis.L.braziliensis -mucocutenous.
Transmission cyclopropagative.Sand fly fever viral disease
mild fever like influenza propagative
Fleas of medical importance
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
Dog flea, cat flea
Human flea Trop. rat flea
dog flea cat flea
Ctenocephalides canis Rat flea
Pulex irritance
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 9th abdominal segment dorsally has a sensory organ-pygedium
• Anterior to this is anti pygedial bristles arise directly from the body
• 9th sternite is club shaped
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
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
Fleas transmited
• Plague (bubonic)• Endemic or murine typhus• Chiggerosis• Hymenolepis diminuta
• Modeof transmissionBiting-blocked fleaMechanical transmissionFaecal
Control of fleas
• InsecticidesDDT(5-10%),γHCH, dieldrin,
diazinon(2%)Applied in floors & walls up to 1ftApplied in rat burrows
• RepellentsDiethyl toluamide
• Rodent control
Human lice
Lice • Small wingless insects
• Three species that solely live on humansPediculus 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.
Head louse- Pediculus humanus capitis• 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
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
Pthirus pubis - Pubic Louse
• 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.
Lice -PH importance
disease transmission: lice act as a vector for - Epidemic typhus - Epidemic relapsing fever, - Trench fever.Pediculosis, irritation and
pruritus.
Control of lice
• Insecticides -Lotion with 0.5% malathion,toapplied and kept on for 24-48 hrs.
•Personal hygiene
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
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
Hard tick
Male
Female
Hard tick
Female Male
Soft tick
• Abdominal wall is smooth
• Dorsal surface has small dot like mamillary tubrercles
•Small, soft and leathery cuticula,
•Mouthparts invisible from dorsal aspect
•The scutum/dorsal schield is `absent
Soft and hard ticks(Agasidae/Ixodidae)
•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
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 4th pair end in suckers
sarcoptes scabei
Female Male
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%),
Preferred sites interdegital, popliteal fold and groin
Cyclops • Class-crustacea
• Pear shaped semi transparent body, forked tail, 2pairs of antennae
• Large cephalothorax & slender segmented abdomen
• Single small pigmented eye
• In females 1st abd. segment has apair of ovisac
Cyclops
Female Male
Cyclops (water flea)
• Vector for:
Dracunculus medinensis
Control
• Physical straining of water through a piece fine
clothBoiling at 60 degree C• Chemical – chlorine 5ppm,alum
4gm/gallon, abate 1mg/l• Biological – gambusia fish• Abolish step well, promote sanitary well