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