Prevent Disease, Disability and Premature Death

MosquitoBiology & Control

Prevent Disease, Disability and Premature Death

Objectiveهدف

Name the biology of mosquitoes to appropriate control measures.

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Overviewمرور

Life Cycle

Behavior

Control Measures

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Importance of Mosquitoes

Found worldwide except Antarctica

Adult female mosquitoes require a blood meal for successful reproduction

May transmit viruses, protozoa, and filarial disease agents

Can have devastating impact, especially during military campaigns

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Mosquitoes Diseases

Mosquitoes are vectors of several important diseases:

Malaria

Dengue

Yellow Fever

Encephalitides (arboviruses)

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Mosquito Growth and Development

Complete Metamorphosis

Egg, larva, pupa, adult

Water is required for larval development

BLOOD

WATERWATER

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Egg Raft (Culex species)

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Single Eggs (Anopheles species)

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Mosquito Habitats

Some require large bodies of still water with emergent vegetation (lake margins, rice fields)

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Mosquito Habitats

Some require “dirty” water (lots of organic materials)

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Mosquito Habitats

Salt marshes (brackish water)

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Mosquito Habitats

Some require water in ditches, streams and other narrow vegetated watercourses (water does not move rapidly)

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Mosquito Habitat

Water in certain plants

L - R: Bamboo, Pitcher Plant, Bromeliads

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Mosquito Habitat

Water in tree holes

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Mosquito Habitat

Some attach themselvesto plants and get their oxygen through the plant

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Mosquito Habitats

Water in artificial containers: cans, bottles, bird feeders, flower vases, and tires

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Mosquito Habitat

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Mosquito Growth and Development

A mosquito larva hatches from an egg…..

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Mosquito Growth and Development

The larvae (“wigglers”) feed on microscopic plants and organic debris in the water; a few are predaceous (Toxorhynchites spp).

Using a respiratory tube, the larvae obtain oxygen from the surface of the water (Anopheles, Culex, and Aedes) or from aquatic vegetation (Mansonia).

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Mosquito Larvae

Anopheles Culex & Aedes

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Mosquito Larvae

Mansonia species

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Mosquito Larvae

Mosquitoes have four larval stages

Development completed in 4 to 10 days

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Mosquitoe Pupae

The pupae are also known as tumblers:

quite active but do not feed

they breathe through two trumpet-like tubes located on the thorax

2 to 5 days as pupae

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Mosquito Adult Emerging

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And flying away…..

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Mosquito Behavior

Defined: “The complex of mosquito actions and activities that meshes with, manipulates, and uses their environment”

Mosquitoes do not think or reason as humans do -- they act/react instinctively to certain stimulus.

We can use their behavior to facilitate surveying for them, trapping them, and killing them.

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Break

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Mosquito Behavior

Feeding behaviorResting behaviorResponse to lightFlight behaviorMating behavior

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Feeding Behavior

Most mosquito species require a blood meal for the adult female to complete the reproduction cycle.

Males do not feed on blood.Almost all mosquitoes need a blood meal to supply protein for each batch of eggs.

Some species can break down muscles for the protein to form one batch of eggs.

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Feeding Behavior

Mosquito females are “pool feeders” when they take a blood meal.

They insert their straw-like proboscis into the host until it reaches capillary blood.

They salivate into the wound, injecting materials to keep the blood from clotting, causing a sub-dermal blood pool to form.

They pull the liquid blood pool through their proboscis to feed.

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Blood-Fed “Engorged”

Culex species Aedes species

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Feeding Behavior

Males and females feed on plant nectar to obtain carbohydrates necessary for their energy requirements.

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Host SpecificityMany mosquitoes are host specific:

Anthropophilic: feed exclusively on humans

Other animalsDomestic animals

Wild animals

Birds

Or any mixture of the above.

Domestic mosquitoes: found in close association with humans

Problems arise when pathogens are transferred between hosts

Mosquito feeding on bird now feeds on human

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Host Attraction

Attractiveness for mosquito based on an identifiable attribute of the primary host

Carbon Dioxide (CO2): Attractive to many species; but all animals exhale CO2L-lactic acid: Thought to be a human attractant; not considered to be importantOctenol: Attractive to some, but not all spp.Other unidentified chemicals specific to hostColors, shapes, sizes, temperatures

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Feeding Periodicity

Feed only during certain times of a 24-hour cycle

Knowing when they’re out feeding helps in targeting surveillance and control

Diurnal -- during the day

Crepuscular -- around sunrise and sunset

Nocturnal -- during the night

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Feeding Location

Endophagic: prefer to feed inside of structures

Rest in room corners, under beds, along roof, wait for host to come inside

Exophagic: prefer to feed outside of structures

Rest in shrubs, trees, pipes, feed on hosts when active outside

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Resting Location

Endophilic: prefer to rest inside after feeding

Rest inside closets, behind curtains, in animal stalls, etc.

Exophilic: prefer to rest outside after feeding

Rest in vegetation, tree canopy, leaf litter, etc.

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Attraction to Light

Light attracts most mosquitoes, as it does most insectsAttractiveness is most pronounced during night hoursSome are so sensitive that they exhibit lunar periodicity

More active with certain phases of the moonIncreased activity w. full moon; decreased w. new moon

However, not all mosquitoes are attracted to lights

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Flight Range

Distance able to fly varies from species to species

Some tend to be weak flyers (</= 100 yds) -- Aedes aegypti and many peridomestic species

Some are strong flyers (Aedes dorsalis, and most salt marsh breeders)...

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Mating Behavior

Adult males usually emerge from the pupal stage ~24 hours before females

Male genitalia must rotate 180 degrees before they become functional -- a slow process

A heavy emergence of males is often followed the next day by a heavy emergence of females

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Mating Behavior

In some species, males form mating swarms near the emergence site to mate with females as they emerge

In some species, the adults mate singly, often near the blood host

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Mosquito Control

Control techniques vary with situationLarge area managementLimited recreational areasResidential

IndoorOutdoor

Field operational -- combinations of above

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Control In/Around Buildings

Reduce vegetation to reduce mosquito resting sites

Outdoor residual pesticides applications in resting places

Screens, caulking, other barriers

Space spraying (“mosquito fogging”)

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Wide Area Mosquito Management

Can be a complex problem

Involves separate sites and groups, and thus requires community involvement and administrative oversight needed

Uses several control strategies, such as…

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Health Education

Education of the public to gainUnderstanding: People must understand the importance and process so they can and will contribute to itSupport: People must support the process so they will clean up their areas, make their property accessible, and take personal precautions to avoid disease

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Survey for Breeding Places

Baseline survey must be made to locate the breeding sites of problem mosquitoes

Oviposition sites (where eggs are laid)

Larval habitats (where are they developing)

Adult surveys (where are they hanging out and when)

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Source Reduction

Channel stagnant water streamsDrain or fill if possibleRemove vegetation that forms harborageStock lakes and ponds with top-feeding minnows or mosquitofish (Gambusia)

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Gambusia Mosquito fish

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Chemical Management

LarvicidingControl the larvae before they become mobile blood-feedersShould be first line of attack

AdulticidingControl the adults before they bite

Proper pesticide must be used in the proper way!

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Larval Control

Use of an appropriate larvicide

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Larval Control

Biological Control:Stock with predators like this Toxorhynchites mosquito species or Gambusia fish

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Summary

Life Cycle

Behavior

Control Measures

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Questions?

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