Life on the Coast: The Necessity of Mosquito Control

Rosmarie Kelly, PhD MPHPublic Health EntomologistGeorgia Department of Public HealthAtlanta, GArmkelly@dhr.state.ga.us404-408-1207

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Overview

• Saltmarsh, freshwater, and mosquitoes• Brief history of coastal mosquito-borne diseases• Mosquito control

– Some history– Mosquito control today– Some data

• Surveillance– Why do it– Some basics (field work)

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Coastal Georgia

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Saltmarsh

Saltmarsh Mosquito Facts

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salt marsh mosquitoes fly 25 miles or more

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A CDC egg survey estimated that the dredge spoil areas have a breeding potential of 100 million mosquitoes per acre.

The coastal marsh is not a “bad” environment. Over 90% of the salt marsh does not breed mosquitoes…only the high marsh areas that trap water after extreme high tides or

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significant rainfall; ie. the areas of the marsh that do not flush with the daily tides.

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Mosquito Oviposition Habitat

• There are two general categories within which mosquito breeding habitats exist: – natural mosquito breeding habitats – man-made mosquito breeding habitats

• Female mosquitoes lay their eggs either on water or on soils that are periodically flooded.

• These breeding areas can be found in habitats that exist naturally, such as within a pond or flood plain, or in habitats that have been created by humans, such as bird baths, water-filled tires, or catch basins.

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Freshwater Habitats

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WHAT MAKES A MOSQUITO?

A long piercing-sucking proboscis, with scales on it!

Scales on the wings and body 3 basic body parts

Head Thorax

2 (=one pair) wings 6 (= 3 pairs) legs

Abdomen ~60 species are found in Georgia~12 are actually a human problem

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Male vs. Female Mosquitoes

male female

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Things Often Confused With Mosquitoes

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Larvae(5-10 days)

Emerging Adult

Egg(2 days -months)

Life Cycle of a Mosquito

Pupae(1-2 days)

live ~1 month

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WHAT DO THEY EAT?

Plant juices & nectar

Females also need blood from other animals

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WHY DO THEY NEED YOUR BLOOD?

And now there will be more mosquitoes!

They use the blood to help develop eggs

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HISTORY OF MOSQUITOES AND MOSQUITO-BORNE DISEASES ALONG THE COAST

• Prior to the Civil War, the fertile delta bottomlands of the lower Altamaha basin were cleared, drained, banked and irrigated for the cultivation of rice, the primary staple crop of the Georgia and South Carolina tidewater section.

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The marshy fields where rice was grown were breeding grounds for mosquitoes carrying diseases such as malaria and yellow fever.

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The semi-tropical climate that made the Lowcountry such an excellent place for rice production also made it vulnerable to the spread of malaria and yellow fever.

Anopheles quadrimaculatus is historically the most important vector of malaria in the eastern United States. Many regions have natural populations of An. quadrimaculatus with predominant populations occurring in the rice growing regions due to cultural growing practices. Fresh water is regularly added to rice fields. Anopheles quadrimaculatus oviposit soon after fresh water has been added.

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What is Malaria?

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Rural cycle

Urban cycle

Sylvatic cycle

A mosquito-borne viral disease of humans. Aedes aegypti is the most common vector.

Initial symptoms include fever, headache, vomiting and backache.

As the disease progresses, the pulse slows and weakens, and bleeding of the gums and bloody urine occur.

Jaundice may also occur.

What is Yellow Fever?

yellow fever had a mortality rate of ~80%

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Even in the absence of diseases, mosquitoes can become so abundant that they cause disruptions in community services and cause severe stress in the affected local human, pet and livestock populations.

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History of Mosquito Control

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City records show the health of its citizens was much improved.

In 1817 the City of Savannah, which also supported a large rice growing culture, approved an ordinance authorizing the City to buy the right of culture from wet to dry from the surrounding landowners.

From 1817 to 1829 the City had expended $72,537 so that only dry rice field culture would be practiced on the adjacent lands.

This successful reduction in mosquito breeding sites was likely the first time that local tax monies were expended to control mosquitoes in the New World.

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Mosquito-control operations are targeted against three different problems:

• Nuisance mosquitoes bother people around homes or in parks and recreational areas;

• Economically important mosquitoes reduce real estate values, adversely affect tourism and related business interests, or negatively impact livestock or poultry production;

• Public health is the focus when mosquitoes are vectors of infectious disease.

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1. Which mosquito species are locally important as the primary source of intolerable annoyance or as vectors of disease.

2. Where the breeding sites of these mosquito species are located.

3. When the mosquitoes are developing in these breeding sites and when the emergence of adult mosquitoes will take place.

4. What mosquito control measures are needed and can be applied effectively, economically, and safely with minimal disruption to the local environment.

5. How much funding will be required to coordinate and execute the plan.

To successfully control mosquitoes it is important to know:

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"A process consisting of the balanced use of cultural, biological, and least-toxic chemical procedures that are environmentally compatible and economically feasible to reduce pest and disease-vector populations to a tolerable level"

INTEGRATED MOSQUITO MANAGEMENT

THIS DOES NOT IMPLY THAT PESTICIDES SHOULD NOT BE USED

Integrated Mosquito Management

SurveillanceSource ReductionAdult and/or Larval

Control Community EducationMapping / Record Keeping

Best Management Practices

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Without surveillance, mosquito control becomes a matter of luck.

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With surveillance, mosquito control becomes more targeted, more effective, and more economical.

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Source Reduction• Modification of water

habitats, including:– Ditching – Clearing vegetation– Filling low areas – Emptying containers – Cleaning gutters

• This is the best method to use when dealing with container breeding mosquitoes.

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Larviciding

• Larviciding is a general term for killing immature mosquitoes by applying agents, collectively called larvicides, to control mosquito larvae and/or pupae.

• It can include the use of natural enemies:– Dragonfly naiads– Mosquito Fish (Gambusia)

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Some Larviciding History• Waste oil or diesel oil products were implemented to

control mosquitoes in the early 1800s• Paris green dust, an arsenical insecticide, was developed as

a larvicide in 1865 and, along with undiluted diesel oil, was used through the 1960s

• Larviciding became prominent when implemented as an area-wide malaria control procedure in the early 1900s

• After 1945, DDT, a chlorinated hydrocarbon compound, was used as both an adulticide and a larvicide - mosquitoes became resistant to DDT, and its use was discontinued in the late 1950s

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Some Larviciding History• In the 1950s, malathion, an organophosphate, was used

increasingly to control both larval and adult mosquitoes - soon, resistance to malathion was observed in saltmarsh mosquitoes.

• Products currently available for use in larval control include:– Biological insecticides

• Bacillus sphaericus • Bacillus thuringiensis israelensis• Natular

– Temephos (OP) – Methoprene (IGR)– Oils– Monomolecular films

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Adulticiding• Control of adult mosquitoes using pesticides• Products available for use include:

– Organophosphates• Naled• Malathion/Fyfanon

– Synthetic pyrethroids• Adulticides can be applied using:

– ULV cold fogging– Thermal fogging– Barrier spray

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Truck Mounted ULV Adulticiding

• Time of day – Mosquitoes must be

present– Dark or close to dark– Temperature inversion

• Conditions – The pesticide has to

impinge upon the mosquito while aloft

– The pesticide has to remain aloft but close to the ground

• Calibration/Droplet size

Controlling Adult Mosquitoes

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Public Education

• Media reports• Community Programs

– Tip and toss (source reduction)– Neighborhood cleanup

• Wear repellent (bite prevention)• School programs• Churches• Nursing Homes• Any place the public congregate

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Mosquito Control Education• It is important to increase the knowledge of mosquito control workers and

other professionals on matters related to mosquito biology, ecology, relationship to disease, and control.

• Georgia Mosquito Control Association– Founded in 1977– Annual meeting– Support for mosquito control programs– Sustaining member of the AMCA– PESP member

• Georgia Department of Public Health– Mosquito surveillance– Mosquito ID classes

• Extension Services

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Record Keeping

• Logging and tracking of citizen complaints and service requests.

• Mosquito collection and trapping.• Insecticide applications and regulatory reports.• Tracking of work assignments, including detailed

daily time and task recording.• Virus testing (sentinel flocks, mosquito pools, etc.)

and related lab reporting.• Mosquito breeding and trap site mapping.

MAPPINGA picture is worth a

thousand words.

1. Map complaints2. Map service calls3. Map breeding sites4. Map anything

useful and mappable

USEFUL TIP – Google Maps

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Surveillance Data – McIntosh County

Ae. a

lbop

ictu

s

Ae. v

exan

s

An. c

ruci

ans

An. q

uadr

imac

ulat

us

Cq. p

ertu

rban

s

Cx. n

igri

palp

us

Cx. q

uinq

uefa

scia

tus

Cx. s

alin

ariu

s

Oc.

atl

antic

us

Oc.

japo

nicu

s

Oc.

solli

cita

ns

Oc.

tris

eria

tus

Ps. c

olum

biae

0

10

20

30

40

50

60

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McIntosh County Mosquito Surveillance

CDC Gravid

Species

coun

t

species CDC GravidAe. albopictus 5 9Ae. vexans 2 An. crucians 47 An. quadrimaculatus 29 Cq. perturbans 7 Cx. nigripalpus 12 Cx. quinquefasciatus 1 64Cx. salinarius 10 Oc. atlanticus 2 Oc. japonicus 1Oc. sollicitans 27 6Oc. triseriatus 1 Ps. columbiae 4

Oc. taeniorhynchus 8767 93

GRAND TOTAL 8914 173

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Surveillance Data – McIntosh County

98%

Surveillance DataAe. albopictus

Ae. vexans

An. crucians

An. quadrimaculatus

Cq. perturbans

Cx. nigripalpus

Cx. quinquefasciatus

Cx. salinarius

Oc. atlanticus

Oc. japonicus

Oc. sollicitans

Oc. taeniorhynchus

Oc. triseriatus

Ps. columbiae

saltmarshmosquito

Gravid Trap

Light Trap

Mosquito Surveillance

Mosquito Gravid Trap Operation

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Gravid Traps

• USE – primarily for monitoring container breeding mosquitoes

• Used in the WNV surveillance program

• NOT USEFUL for monitoring most nuisance species

• NOT USEFUL for monitoring EEE

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Mosquito Light Trap Operation

Light Traps

• USE – general surveillance for host-seeking mosquitoes

• Used in the EEE surveillance program

• USEFUL for monitoring most nuisance species

• NOT USEFUL for monitoring WNV

Larval Surveillance – “get them before they get you”

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WHY MOSQUITO SURVEILLANCE?

•Surveillance is used to define the nature and extent of the mosquito problem.

•Surveillance is used to gauge daily mosquito control needs.

•It provides a basis for evaluating the effectiveness of control operations.

•It provides a basis for evaluating the potential for transmission of mosquito-borne diseases.

Mosquito Surveillance

Mosquito surveillance is the cornerstone of mosquito control.

No mosquito control program can operate effectively without a surveillance program.

Mosquito surveillance can reveal:

• The species of mosquitoes that are active in a community

• The presence of disease vector species

• The presence of mosquitoes infected with arboviral diseases

• The breeding habitats of the local species

• The size of the local mosquito population

• When to apply pesticides to control the mosquito population.

Knowing what mosquito species are present andwhere they are breeding is essential to a well-plannedmosquito control program.

ALL MOSQUITO SURVEILLANCE SHOULD HAVE A PURPOSE:

•MOSQUITO CONTROL – LARVAL OR ADULT•ARBOVIRAL SURVEILLANCE•PUBLIC EDUCATION

MOSQUITO SURVEILLANCE SHOULD NEVER BE DONE WITHOUT A SPECIFIC GOAL IN MIND.

Any Questions?52

http://health.state.ga.us/epi/vbd/mosquito.asp

http://www.GAmosquito.org

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Field Work• Adult surveillance - set traps

– CDC miniature light trap– CDC gravid trap

• Larval surveillance• Landing counts

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