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  • Since 1986, several outbreaks of malaria have occurred in the traditionally non-mal;rious areas. These were related to hydrological changes below dams causing pooling in the rocky and sandy river bed linked with water diversion and aggravated by droughts. In addition human migration between the downstream settlements and upper non malarious areas promoted parasite carriage.
  • Infection is associated with prolific breeding of the vector in blocked drains, sewage pits and polluted stagnant water collections that are common in the poorly planned urban environment. such sites also favour breeding of Armigeres mosquitoes.
  • the outdoor agricultural lifestyle and rural dwellings carry high risks of man-mosquito contact.
  • The global emergence of dengue fevers as an urban public health problem is associated with Aedes breeding. Modern lifestyles with widespread use of 'thowaway containers that end up in refuse are ideal breeding sites. 90% of Aedes breeding in in Sri Lanka occur in discarded receptacles, empty coconut combs and used tyres made use of for varying purposes.
  • Mosquitoes

    1. 1. Rumala MorelDept. of ParasitologyPeradeniyaY2S2Mosquitoes of MedicalImportance in Sri LankaAedesAnophelesCulex
    2. 2. MEDICAL ENTOMOLOGYStudy of insects and otherarthropods of medical importanceInsects: Mosquitoes, Flies, Midges,Lice, Bugs, FleasOther arthropods: Ticks and Mites
    3. 3. Objectives: List the major mosquito borne diseasesthat occur globally List the mosquitoes of medical importancein Sri Lanka indicating the diseases theytransmit Outline the life cycle of a mosquito Describe the breeding & biting habits ofthe medically important mosquitoes in SriLanka Outline the strategies used for control ofthese mosquito species in Sri Lanka
    4. 4. Anophelines-AnophelesMosquitos – found globally in all climates>3000 spp. only few of medical importance Culicines - Culex- Aedes- Mansonia- Armigeres
    5. 5. Role of mosquitoes in disease transmission2500 yrs ago Susruta suggestedtransmission of malaria by mosquitoesbut no definite proof until end of 19thC1859- James Emerson Tennent in‘Ceylon: An account of the island’….retiring punctually at sunset andsleeping under mosquito ‘curtain’ is avaluable prophylactic against fevers…
    6. 6. Medical importance of Mosquitoes biting nuisance- pests/allergy vectors of diseasetransmit disease causing organismsMosquitoes as biological vectorsEssential part of the life cycle takes place inthe vector- multiplication or developmentor bothSpecific time period necessarybefore vector can infect another host
    7. 7. Mosquitoes as vectors of disease:some important discoveries1878 Patrick Manson- filarialparasites1897 Ronald Ross- malaria1900 Reed & team- yellow fever1902 Graham- dengue
    8. 8. Aedes aegypti Dengue Dengue virusesChikungunya Chikungunya virusA.albopictus Dirofilariasis Dirofilaria repensMosquito borne diseases in Sri LankaMOSQUITO DISEASE INFECTIVE ORGANISMAnopheles culicifacies Malaria Plasmodium spp.Culex quinquefasciatus Bancroftian Wucheraria bancroftifilariasisC. gelidus Japanese Jap Encephalitis virusC. Tritaeniorynchus encephalitisC.pseudovishnuiYellow fever – globally impt. mosq.borne diseaseNot found in SL
    9. 9. Biological characteristics influencingdisease transmission only females suck blood (blood required foregg maturation) breeding habits: preferred water type host preference – anthropophilic- zoophilic blood sucking behavior- daytime/nightindoor/outdoor survival- 3-4 weeks (to allow development ofpathogen) flight range- 0.5 - 1.5 km
    10. 10. Morphology of adult mosquito
    11. 11. SEX DETERMINATION - AntennaClassification of mosquitoes -1. SEX"plumose" (hairy) - male"pilose" (not very hairy)female
    12. 12. Palps (sensory organs just lateral to the proboscis)Classification of mosquitoes – 2. GENERAA female mosquitowith long palps = AnophelesA female withshort palps =CulicineAnopheles mosquitoesrest and bite with theirbottoms up @ 45 degreeangle to the skin
    13. 13. Life span1 month150-300laid every 48-72 h4 stages1-3 weeks2-3 days2-3 daysMosquitoLife CycleWater isessentialfor breeding
    14. 14. Eggs:laid singlywith floatsEggs:in clustersLarvae:parallel tosurfaceno siphontubeLarvae:siphon tube +Adult: rests @45º angle tosurfaceAdult: restsparallel tosurface
    15. 15. Aedes rests parallel to surfaceAnopheles culicfacies alsorests parallel to surface like culex
    16. 16. Anopheles species of importance in Sri LankaAn. culicifacies- major vector of malariavectors of minor importanceAn. subpictusAn. annularisAn. vagusAn. tesselatusMajor vectors in other countriesAn. gambiae- vector of human malaria andBancroftian filariasis in Africa
    17. 17. Characteristics of importance for a malarial vector density longevity biting habits- anthropophilic (manbiting)- outdoor/indoornight biting mosquitoesKeys/charts used for species identificationRests on walls – Indoor Residual SprayingEffective control method
    18. 18. Anopheles culicifaciesDistribution: Sri Lanka, India, MyanmarPakistan, Middle East, Nepal, ThailandAdult: small- mediumwings & female palps - bandingresting position culicine-likeBreeding: shallow, sunlit, clear fresh waterEg. Edges of slow flowing streams/rivers;rain water collections in ground pools and pits
    19. 19. Dry zone: endemic speciespresent throughout year but highdensities with rains (NE monsoon Oct-Jan)Intermediate zone: seasonal breedingWet zone: not normally found but breedingoccur with failure of monsoons due topooling in river bedsFound up to 900 m heightDistribution in Sri LankaAnopheles culicifacies
    20. 20. Rain water collections in pits,construction sites, hoof printsin dry zoneStream/river bed pools;seepage pools atmargins of lakes,reservoirs;open irrigation canalmargins
    21. 21. Malaria vector breedingin quarry pitsKurunegala (NWP) andAnuradhapura (NCP)
    22. 22. Malaria vector breeding in Agro wellsMatale, Anuradhapura district
    23. 23. Wet zone-rock/sand river bed pools during droughtspooling below dams/barragesKotmal oya- below dam
    24. 24. malaria vector breeding downstream of dams-An. culicifacies
    25. 25. Below dam at Nilambe oyaIlagolla- malaria outbreakdue to mosquito vectorbreeding in rock pools
    26. 26. Culicines- 20 generaIn Sri Lanka > 115 species Culex Aedes Mansonia Armigeres
    27. 27. Culex quinquefasciatusVery common urban domestic mosquito throughoutSouth/SE Asia- vector of bancroftian filariasisSmall, brown, absence of markingsBreeding: eggs in rafts (75-100 eggs)highly polluted (organic matter) stagnant watereg. blocked drains, cess pits, waste water pitsHabits: night biter, outdoor/indoorbites man, cats/dogsRests in shade eg. indoors in dark cornersclothes, under furniture etc.
    28. 28. Culex quinquefasciatus Biological vectorLymphatic filariasis:Microfilaria ingested with the blood meal develop intoInfective larvae L3 in 10-12 days and emerge fromproboscis during the biteONLY development NO multiplication
    29. 29. Breeding sites of Culex quinquefasciatusStagnant,polluted water(sewage)
    30. 30. Culex quinquefasciatus breeding sitesDirty water in blocked drains, cess pits etc.
    31. 31. Culex tritaeniorhynchusCx. gelidusCx. pseudovishnuiBreeding: paddy fields, marshes,husk-soakage pitsHabits: night, outdoor/indoorbites animals; pigs/cattle(zoophilic)Vectors of Japanese encephalitis
    32. 32. Japanese encephalitis:Epidemiological cyclePigs important amplifier hostsMosquito vectors:Cx. tritaeniorhyncus;Cx.pseudovishnui- paddyfield breedersCx. gelidus- muddy poolshusk pits
    33. 33. Japanese EncephalitisCulex gelidus
    34. 34. Vectors of Japanese encephalitis breed in paddy field
    35. 35. Aedes spp.Ae. aegypti Ae. albopictusSmall, delicate, black & white banding on legs.wings clearVectors of-Dengue fever, Chikungunya, Dirofilaria repensYellow fever (not in Sri Lanka)Breeding: eggs laid singly (no floats)damp surfaces that get submergedrain water collections in containers
    36. 36. Vectors ofDengue & ChickungunyaAedes aegyptiAe albopictusContainer breeders, clean waterartificial- tyres, tin cans, plastic wasteIndoors- flower vases etc.Natural- cut bamboo stumps, leaf axils
    37. 37. SL: dengue endemic since 1989Transovarian transmission of arbovirusesAedes breeding sites
    38. 38. Aedes breeding in householdsindoorsoutdoors
    39. 39. AedesBreedingoutdoors
    40. 40. Vector of Brugian filariasis& DirorfilariasisWater plants:PistiaEichorniaSalviniaMansonia spp.M uniformisM annuliferaBrown, speckled wings (light/dark scales)Breeding: aquatic plantseggs laid in clusters on undersurfaceleaves of water plantsLarvae/pupae attached to plant roots
    41. 41. Armigeres subalbatusVery common dusk/night biterPest & vector of Dirofilaria repensBreeding: polluted waterDirofilariasisDirofilaria repens: commonparasite of dogstransmittedby Aedes,Armigeres,MansoniaCauses subcutaneousnodules in humans
    42. 42. Reduce mosquito densityPathogen control in humansPrevent man-mosquito contactControl of mosquito borne diseases
    43. 43. Reduce vector density 1Adult control – Malaria control(1) Insecticide impregnatedbed nets – treat every 6/12(2) Indoor Residual Spraying
    44. 44. Reduce vector density 2Eliminate breeding sitesDestroy larvaeAedes spp.• Properly dispose of old tires, cans, bottles,water-collecting rubbish, and otherunused/unwanted containers.• Eliminate breeding in standing pools of waterEg. air conditioners, refrigerators – add surfaceoil layer• Clean birdbaths, vases, plant pots, rainbarrels, kiddie pools etc. ONCE A WEEK
    45. 45. SummaryMosquitoes ofMedical ImportanceAedesAnopheles culicfaciesCulex